August 18, 2008 Indexing and Reading Spark Plugs
The first step to index a spark plug is to draw a black line on the plug with a Sharpie or some other permanent marker. The line must be directly in line with the plane of the ground strap top. That way when the plug is indexed and installed in the head correctly, the black line is always on top. Unfortunately not all heads and spark plug holes are tapped the same as well as the thread starting point of spark plugs. You may screw in and tighten a plug and the black line is on the bottom meaning that you need to compensate for the 180° difference. That's where indexing washers come in. A set of indexing washers contains three thicknesses of washers to rotate your plugs 90°, 180° or 270°. If the plug is off by 180°, add the middle thickness washer and now the plug is properly indexed and the black line is on top. From a personal perspective, I'm a little anal about it but I also write the cylinder number on each plug so if I take the whole set out, I put them back in the same hole and don't have to re-index them. Moroso offers part numbers 71910 for flat seat plugs and 71900 for tapered seat plugs. Other than installing thermo-coupler sensors measuring EGT (Exhaust Gas Temerature), the only real way to know what is happening inside your engine is to read the spark plugs. Both the fuel mixture and the ignition timing result in coloring of the spark plug’s porcelain and ground strap. The trick is to how to get the correct coloring without going into detonation and destroying the engine or by going too rich and raising the ring lands. Spark plugs can only be correctly read if the car has been shut down immediately at the end of a run without driving it back to the pits. Get off the track and coast to a place you are safely out of the way and either read the plug there or change one or two with some you have in your pocket so you can read these uncontaminated plugs when back to the pits or simply tow the car back. It may take a couple of runs to get see the spark plug color. The porcelain around the plug’s center electrode can be divided into three areas for reading. The area that is closest to the tip is affected by the idle and transition carburetor circuits and is of no real concern to a racer. If this area is gray then you drove the car back to the pits and you cannot correctly read the plugs. The middle area is only colored when you drive down the road at around a steady 30-40 mph and is normally affected by the primary circuit jetting with the power valve closed and this is really of no concern to the racer. The area you are interested in is that third that is all the way up inside the plug where the sun dosen't shine. This area is colored when all is wide open under full power because the combustion chamber heat totally cleans off the other two areas. It will take a special plug reading flashlight with the magnifying glass to view it correctly. Plugs cannot be correctly read by just quickly looking at them with the naked eye. You see people doing it all the time because they don't know what they are doing. Normally aspirated cars should have a light gray or tan hydrocarbon ring or as some call it a "fuel ring" all the way up inside around the third area closest to the point where the porcelain is attached to the metal jacket of the plug. The actual color may depend on type of fuel you use. This fuel ring should appear like a light shadow. Most VP C-15, C-16 or C23+ fuels will show as a light gray when correct. This fuel ring starts to color on the porcelain side that is below the ground strap and works its way around either side of the center electrode until it completely joins. Sometimes it may take two or three runs to see a good coloring. Note: New engines or engines that pump a little oil may show a thin oily line way down inside on the porcelain where the porcelain meets the metal wall of the plug. This oil line has nothing to do with the air/fuel mixture but may be confused with the fuel ring you are looking for. If you are having a hard time figuring out if what you are reading is correct or because you are not sure if the plug heat range is correct then tow the car back to the pits and drop the headers and look inside the pipes. If they are black then you are too rich, if they are light gray or white then you are too lean. The pipes should be a medium to dark gray or tan color. Normally the white area of the porcelain has a chalky appearance. If you see the porcelain take on a shine then it is time to change the plugs because the glass that is in the porcelain has been melted and has glazed the surface. If the car has been running rich (due to lots of idling or incorrect fuel mixture) then it is possible to glaze the plugs and short them out during a run because of the sudden heating of the plug with the soot on the porcelain. This glazing appears to be a glossy coating on the porcelain with a splotches of color of greenish yellow or brown. These two different glazings will cause the plug to short out and misfire and raise ring lands or make a popping through the exhaust when going down the track. Ignition timing is directly responsible for the heat in the combustion chamber and therefore the color of the plug’s ground strap and the color of the first few threads on the outside of the plug. The ignition timing can be checked by looking at the color of the plug’s ground strap and the position of the "blue line" on the strap. The blue line really indicates the point at which the strap has reached annealing temperature of the metal. To help to understand this, think of a bar of steel (ground strap) on a table that is being super heated with a acetylene torch at one of the tip ends. As the end heats up and the heat starts moving down the bar you will see a blue line across the bar at some point down the bar away from tip with the torch. This blue line reflects the temperature that is the annealing point of the metal. As the temperature increases the blue line moves further down the bar away from the torch. Similarly, the blue line moves down the spark plug ground strap as you put more heat in the engine. If you are using a gold colored ground strap like with an NGK spark plug then not enough timing will show the ground strap as still gold or going light gray maybe with a few bubbles on it after a run. As you advance the ignition and put heat in the engine the plug ground strap will turn darker gray as well as the metal at the end of the threaded area. As the metal turns medium to dark gray you should start looking for the blue line (band) around the ground strap. Ideally, you want this blue line to be just below where the ground strap makes the sharp bend and above the weld. If you advance the ignition too far the blue will disappear off the strap and the strap will pick up rainbow colors (blues and greens). The next step beyond that is to start melting the strap from the tip end and detonation. When you are close to the correct timing then only change the timing by one degree at a time. If your ignition system has the capability of adjusting the timing of each cylinder independently (ICT), then you can use that feature to have the blue line in the same position on all the plugs. First, adjust the basic timing to get as many of the plugs to have the blue line just at the sharp bend in the strap. Now adjust the ICT to move the blue line to the same point on the remaining plugs. Once all the plugs read the same you can advance the ignition a little at a time to put the blue line just above the weld on the strap or whatever point gives you the best performance. The round flat circular area of the plug at the end of the threads should be dark gray or flat black and should not be sooty. If it is sooty then it can mean that your plug has not been tightened enough and you are sucking and blowing fuel and air past the threads of the plug. Detonation shows up on the plugs as spotting on the porcelain. There are two different types of spotting seen. One type appears as just black spots and the other appears as little bright spots like diamonds. The black spots (look like pepper sprinkled on the plug) indicate a little too much heat on the plug which causes detonation by having the heated plug fire off the mixture prior to the spark firing. This creates two flame fronts that collide and can cause great amounts of damage. If you see black spots on the porcelain and you know the tune-up is correct then you may need a colder plug. If you are not sure, then increase the carburetor jet size slightly, take out some timing, or go to a colder plug. If you hold the plug in the sun and you see what appears to be small diamonds on the porcelain then your detonation is severe enough to be blowing off the aluminum from your piston and you need to add fuel and/or take out timing immediately. If you keep on adding timing until your finish MPH falls off but you still have no color on the plug’s ground strap but the porcelain has good color then your plug is too cold. If you have lots of color on the ground strap but the porcelain is clean and white then the plug heat range is too hot. The heat from the plug is cleaning off the fuel ring from the porcelain.
August 8, 2008 How to Dyno Your Motor and Run Your Car From Your Desk
I had already setup my car in the Drag Race Analyzer and backed into my previous horsepower numbers by using actual ET and incremental numbers. I just had to enter all of the motor data into the Engine Analyzer Pro to determine Peak HP at what RPM and Peak Torque at what RPM. Taking those figures then enter them into the Drag Race Analyzer to predict the runs. Click Here to see the results in .pdf format of my original set up at 36° timing with a 7600 rpm shift and 5400 rpm launch. I had all of the details of air flow of the heads from AFR and all of the cam specs from my Cam Motion cam card. The software predicted that I'll have 708 Peak HP @ 5650 rpm and 576 Peak ft/lbs Torque @ 5650 rpm and run a 1.16 60 foot, 5.09 @ 137.10mph in the 1/8th mile and 8.06 ET @ 163.80 mph in the 1/4 mile. This is where it gets interesting. I had already changed my launch rpm six times and my shift rpm four times to find the best ETs. Then I ran the dyno and the resultant sheets that you can download. Afterwards I was thinking, what if I played with timing, what would happen? I started at 36° then ran the timing all the way up to 40° and down to 34°. When I lowered the timing from 36° to 34°. The Peak Torque climbed to 582 ft/lbs and I gained 1 HP. I then adjusted the numbers in the Drag Race Analyzer and the ET picked up .01 to a 5.08 in the 1/8th and picked up .02 in the 1/4 to a 8.04. Of course this software is like any other, garbage in, garbage out but if you have all of the data and you spend the time to enter it right, you can learn a lot about your car for a lot less money and then make the right choices in new parts before you buy them. The nice thing about the whole package is that you can play with one or many changes for your car to get the most bang for the buck especially concerning cams, gears, tires, carburetors, jets, heads etc.
July 27, 2008
So much of the difference between winning and losing is mental. I'm not trying to discount that you must have a good race car but you must be prepared as well. I know for a fact that when I feel confident in my car and have a positive mental attitude, I win many more rounds. The mind is a powerful tool to either work for you or against you. Michael Beard at the Staging Light, wrote three papers for his psychology class while at Bucknell University. All of the papers deal with the psychology of drag racing and are very worth while reading if you are trying to improve your win loss ratio. The first paper is Problem Solving - How I improved My Driving, the second is Attribution Theory - Develop A Winning Attitude and the third is Analysis of a Learning Environment- Inside The Drag Racer's World. Let's put it this way, if by reading these, you win one extra round, it was worth the read. Right?
July 5, 2008 Engine Oil Is The Life Blood Of A Racing Engine
The filter provides for 100% filtration through a duplex woven, deep pleated
30 micron surgical stainless steel filter media. The base of the filter
includes a rare-earth magnet. These extremely powerful and compact
rare-earth magnets will capture the smallest of metal particles and stop the
metals from re-entering your engine. I my case, all of the minute bearing
particles stuck to the bottom so I was able to immediately identify the
problem and correct it before completely trashing the motor. This is just one of those products that in my opinion is cheap insurance that in the long run can save you a ton of money.
May 28, 2008
When working with aluminum, keep in mind that it is a relatively soft metal that scratches easily so when smoothing or polishing, keep in mind which way any swirl marks may appear. The plates I polished were certified 6061-T6 1/4" aluminum sheet. I spent about 3 hours or so on the mid-plate and another hour and a half on the front side only of the front engine mounts. If you were to look at the raw aluminum under a microscope, you would see what could easily be represented as a saw blade with ridges, peaks and valleys across the surface of the metal. The process of polishing basically reduces the height of the peaks drastically reducing the depth of the valleys. This allows the valleys to be cleaner and reflect light rather than absorb it. I started the process by dry sanding the plate with 320 grit automotive sanding disks (available at any NAPA store) using an orbital sander. I sanded each side as smooth as possible using 3 or 4 disks per side. After this first step the difference in smoothness is very noticeable. The next step was to wash the plate thoroughly with Simple Green and water. Between each step it's very important to remove all of the black cuttings and keep the plate clean. The next step was to wet sand with 1000 grit hand sheets using mineral spirits as a lubricant (not water). Mineral spirits suspend the cuttings allowing them to be washed away so that the don't clog up the microscopic valleys. Keep your motions going in one direction for a more even finish. I used 3 or 4 sheets per side. After completing this step, wash the plate thoroughly with mineral spirits. Repeat this entire step now using 1500 grit then repeat the whole step again with 2000 grit. For an even brighter shine, you can do it one more time with 2500 grit, I didn't. I buy Carborundum sanding paper from McMaster-Carr
May 8, 2008 Thrust bearings are used to control end play in the crankshaft. End play is important because it limits the fore and aft movement of the crankshaft in the block. If an engine is assembled with too much end play in the crank, or if the thrust bearing fails, the forward movement of the crankshaft in the block can chew up the main bearing caps and block. Excessive end play can also cause connecting rods to fatigue and break, and wrist pins to work loose and score the cylinders. For years engine and transmission re-builders have struggled to determine the cause of crankshaft thrust bearing failures. Often, each has blamed the other for the resulting damage. To get to the bottom of the issue, the Automotive Transmission Rebuilders Association (ATRA), the Engine Rebuilders Association (AERA), the Production Engine Remanufacturers Association (PERA), the Automotive Service Association (ASA) and bearing manufacturers got together and came up with a list of possible causes and remedies for thrust bearing failures. Their findings are published in AERA tech bulletin TB-1465R (March 1998). What They Found
Surface Finish Manufacturers of crankshaft micro polishing equipment all say polishing the thrust surface on the crank is just as important as polishing the journals. They also say machine polishing is more accurate and consistent than hand-polishing. Many engine builders use a micro polishing machine for polishing crank journals and thrust surfaces. The problem with polishing cranks manually is that it is totally operator dependent. It is more of an art than a science and it is hard to control. These machines use a separate polishing arm for the thrust surface. Micro polishing the thrust surface totally eliminated any thrust bearing failures for most builders. Misalignment The thrust surface on the crank must be ground perpendicular to the crank, so close attention needs to be paid to the grinding wheel. The side of the grinding wheel must be dressed at exactly 90 degrees to produce a thrust face that lines up properly with the thrust bearing. The grinding wheel side face must be dressed periodically to maintain a clean, sharp cutting surface. A grinding wheel that does not cut cleanly may create hot spots on the work piece leading to a wavy, out-of-flat surface. Coolant should be used to minimize heat build-up. The crankshaft grinding wheel must also be fed into the thrust face very slowly and allowed to "spark out" completely. Also, only a minimal amount of metal should be removed to clean up the surface. According to the AERA report, the thrust surface on many remanufactured crankshafts often does not require grinding. The crankshaft can be installed with standard bearings or oversize thrust bearings. But if oversized bearings are used, the crankshaft thrust surface must be re-machined to compensate for the increased thickness of the bearing. If not, the crank may not have the proper amount of end play. When the thrust bearing is installed, AERA recommends a several step process to assure proper alignment.
Overloading
a) Excessive torque converter pressure; b) Improper throw out bearing adjustment; c) Riding the clutch pedal; d) Excessive rearward crankshaft load pressure due to a malfunctioning front-mounted accessory drive. AERA says people sometimes blame torque converter ballooning, the wrong flexplate bolts, the wrong torque converter, the pump gears being installed backward or the torque converter not installed completely for overloading the thrust bearing. Although all of these conditions will increase loading on the thrust surface, it will also cause the same loading on the pump gears. This can cause serious pump damage within minutes or hours. Diagnosis
Examine the front thrust face on the crankshaft for surface finish and geometry. This may give you a clue as to the original quality of the failed face. Once you are satisfied that all the potential causes inside the engine have been eliminated, ask about potential external sources of overloading or misalignment. The main one here is the transmission.
Vehicles with manual transmissions may also experience thrust bearing failures due to high clutch pressures if someone has installed a "performance" clutch with very high spring pressures. Who is To Blame? Transmission oil pressure does exert a force that tries to expand the converter like a balloon (which is why converter ballooning is often blamed). The front of the converter has more surface area than the rear because the converter neck is open. This is why the converter pushes forward against the crankshaft. But the amount of force usually is not great enough to cause excessive wear on the thrust bearing. General Motors says the thrust bearing on a big block Chevy is designed to withstand a sustained force of 210 lbs. against the end of the crankshaft. That would require an internal pressure of 100 to 119 psi inside a torque converter which normally operates at 50 to 80 psi. So the only way the torque converter could cause a problem is if it is experiencing higher than normal operating pressures. One of two things can cause excessive torque converter pressure: a restriction in the cooler circuit; or modifications or malfunctions in the transmission that increase line pressure. One way to combat restrictions in the cooler circuit is to run larger cooler lines. Another is to install an additional cooler in parallel rather than in series. This will increase cooler flow considerably and reduce the risk of over cooling the oil during cold weather. The external parallel cooler may freeze up under very cold conditions, but the cooler inside the radiator will still flow freely. Modifications that can increase converter pressure include using an overly-heavy pressure regulator spring, or excessive cross-drilling into the cooler charge circuit. Control problems such as a missing vacuum line or stuck modulator valve can also cause high pressure. Bearing Designs In recent years, bearing manufacturers have switched to "contoured" thrust bearings that can handle higher loads. Some use thrust washers or a three-piece flange assembly. The contact surface has multiple tapered ramps and relatively small flat pads, or a curved surface that follows a sine-wave contour around their circumference. This allows the bearing to maintain an oil wedge and support greater loads. On Chrysler 3.5L engines, a six-piece thrust bearing is used. The two thrust flanges are loosely held on each bearing with four small tabs so they can move around and align themselves to the crankshaft. They also incorporate a "ramp and flat" design that increases their load carrying capacity by a factor of three compared to that of a conventional, flat-faced, thrust bearing. Be sure to use an equivalent bearing when rebuilding one of these engines because Chryslers FWD transmissions tend to load the thrust bearing pretty heavily. The upper bearing is grooved and the lower one is not.
The chamfer should be toward the rear thrust face only. It is very important not to contact the bearing surface with the end of the file. The resulting enlarged ID chamfer will allow pressurized engine oil from the preexisting groove to reach the loaded thrust face without passing through the bearing clearance first.
Other External Problems
It's easy to check for excessive voltage in the drivetrain: Connect the negative lead of your DVOM to the negative post of the battery, and the positive lead to the transmission. You should see no more than 0.1 volts on your meter while the starter is cranking. For an accurate test, the starter must operate for at least four seconds. It may be necessary to disable the ignition system so the engine won't start during the test. If the voltage is excessive, check or replace the negative battery cable, or add ground straps from the engine to the frame, or the transmission to the frame. Some systems may reach 0.3 volts momentarily without having a problem. For added assurance, improve the ground with a larger battery cable or additional ground straps. Although the greatest current draw is usually while the starter is cranking, current in the drivetrain can occur while accessories are operating. That's why you should perform this voltage-drop test with the ignition on, and as many accessories operating as possible. Again, the threshold is 0.1 volt. One final problem that may occur is current though the drivetrain, without measurable voltage. If the grounding problem is in the chassis but the engine and transmission ground is okay (or vice-versa), the vehicle may pass the test. What happens here is the ground circuit can be completed through the drive shaft and suspension. To test this, measure the voltage drop with the drive shaft removed. Both the drivetrain and frame must pass the 0.1 volt test. This is where a ground strap from the engine or transmission to the frame does its best work.
May 2, 2008 Taking the Mystery Out Of Drag Racing With Alcohol
I have run across more racers than I can count who have said to me, "I don't know anything about racing with alcohol so I race with gas." I wanted to write this article to take a lot of the mystery out of the subject as racing with alcohol is really not that difficult. I started racing with methanol back in 1985 after Danny Bastianelli, a good friend of mine, talked me into it. At that time we made tons of mistakes and learned a lot the hard way, but we also ran pretty quick. So,,what is it? Methanol, racing alcohol, is comprised of one carbon atom, one oxygen atom and four hydrogen atoms (CH3OH), a clear, very toxic liquid fuel formed by catalytically combining CO with hydrogen in a 1:2 ratio under high temperature and pressure. It melts at -97.8°C (-144.04° F) and boils at 67°C (152.6° F). The boiling point is important so remember it for later in the article. Methanol mixes and absorbs water very easily. These are all important considerations that you must take into account before beginning to race with Methanol" 1.) Methanol makes approximately 15% more horsepower than racing gas. You will go quicker immediately. It is also a very forgiving fuel and much more consistent as it is much less vulnerable to weather changes than gas. 2.) Slightly rich methanol engines typically run with much lower exhaust gas temperatures than with a gasoline engine, while the exhaust gas volume is higher. On the top end with methanol, a 1250° EGT is expected vs.1400° to 1500° for gas. The result is much lower coolant temperatures. On a typical run, pull out of staging at 150°, stage at 160°, go through the lights at 180° and cruise down the return road at 160°. Overheating is an issue of the past. 3.) Methanol evaporates very quickly when directly exposed to the atmosphere. As a result, fuel jugs and fuel caps must be kept closed when not transferring fuel. 4.) Methanol is corrosive so keep your fuel system full with fuel or it will evaporate, oxidizing certain types of metal such as pot metal, aluminum or steel (not stainless steel) and will dry or harden rubber seals and hoses. Corrosion can be kept to a minimum by mixing 2 oz. of top oil to each 5 gallon jug of methanol. This amount of top oil will not effect performance but will adequately lubricate the fuel system and the cylinder bores. After you are finished racing for the day, liberally spray your induction system with WD-40, turn the motor over for 5 seconds then repeat the process 2 more times. This will protect your carburetor or throttle body and keep any rust from forming on the cylinder walls. 5.) You will use almost twice as much methanol as you would racing gas. The optimum air/fuel ratio for methanol is 6.4: 1 while gasoline is 13.2:1. As a result, you need to be able to flow enough fuel so as not to starve the motor. If racing with a carburetor use a high flow electric fuel pump such as a Magna Fuel or Barry Grant or even a mechanical belt driven pump with a 10-AN supply line.. If you use an electric pump, you need a good quality bypass regulator (I recommend only the Magna Fuel) set @ 8 lbs. adjusted with the motor running on idle. A bypass is extremely important because methanol boils at 152.6° F and it doesn't take very long for methanol under a lot of pressure to reach that point. A 750 cfm Demon for my 370 cubic inch small block would use 94 jets on gas or my 775 cfm Demon on methanol would use 180 jets. I learned the hard way that the ultimate fuel system for methanol is a Ron's Flying Toilet. It's worth .2 in ET. My 385 small block uses #35 injector nozzles and a .086 bypass pill.
6.) Seeing that you are
pumping twice as much fuel through the motor as with gas, if you aren't
careful, the oil will easily get polluted
When racing with a mechanical fuel injection system, such as a toilet, you simply close the fuel shut off enough so that your idling EGT is 500°. According to both Valvoline and Lucas, do not use synthetic oil if you race with methanol. They both recommend 20W-50 petroleum based racing oil and they both also recommend for the oil to be changed every 30 runs as a maximum. Please see my tech article below dated April 2nd regarding vacuum pumps with alcohol motors. Click the images for full size 7.) Methanol burns a little slower than gasoline which means that a little more advance timing is needed for optimum performance. Start out on the rich side with less advance. Sneak up on it until the car slows down, then back up slightly. Each motor is different. Some smaller cubic inch small blocks can run 38-40°, bigger cubic inch small blocks and big blocks 34-36° and blown or turbo charged cars in the 30-32° range. There are a lot of variables such as compression, heads etc. 8.) Methanol as a fuel, responds very well to compression. 14.0:1 - 17.0:1 vs 12.5 - 13.0 on gas. 9) Methanol requires colder plugs. Typically two steps colder than what you would run on gas. My small block uses a NGK BP-9 series plug. 10.) To read spark plugs when using methanol, a proper tune up will show heat discoloration three threads down from top of the electrode end of the plug. You should also see the heat mark on the ground strap just past the top of the bend and a slight coloring of the porcelain on the electrode side near the tip. 11.) A dead cold motor will not start on Methanol. Don't even try it as you will kill a starter in the process. You must prime the motor with gasoline. Ron's Fuel Systems makes a primer kit that contains a 1 quart fuel bottle, a small Purolator fuel pump, hose with fittings and a push button for your dash. The kit also includes a jet to install in your intake but for my car I opted to use an Edlebrock # 70063 nitrous spray bar so that when you prime the motor the fuel is atomized. You just need to cap one end of the spay bar. Once the motor starts and runs, the latent heat from the block will allow the motor to then restart without having to re-prime it. 12.) Caution...prolonged breathing of methanol fumes or prolonged exposure to the skin can cause blindness. Methanol burns with a clear ever so slightly blue flame that is very hard to see. Handle methanol with caution and common sense just like you would with gasoline. Happy racing.............
April 26, 2008 Oil is the life blood of any engine. I don't think anyone who reads this will disagree with that statement. Over the years, the one thing I found that all engine builders agree on is, a sure way a bracket or Super Class racer can guarantee to prolong the life of a motor is to use an oil accumulator. According to some engine builders, using one can double the expected life of your engine, but of course that statement comes with a large disclaimer. Regardless, whatever we can do to prolong an engine's life is a good thing.
Once mounted in your car, you pressurize the
top of the unit with approximately 6 lbs. of
The only question you are left with is, how are you going to control when to the unit is operated. Once you start the car for the first time with the extra oil, you must close the unit before you shut the motor off. If you don't, of course the extra oil will be in the oil pan and not available in the accumulator to prime the bearings. Depending on your car, the manual method of closing the ball valve just may not be practical. Just think of how many times you have to start and stop the car just in the staging lanes.
In the case of a fuel injected car, such as mine, a separate switch is required because I have to shut the car off with the fuel shut off not the ignition switch. According to the latest prices on the JEGS website, your investment would be $191.99 for the accumulator, $81.99 for the adapter and $107.99 for the solenoid kit. In my book, that's pretty cheap insurance. April 19, 2008 The dos and don'ts, hows and whys of engine bearings Here is the best information that I could find for myself and of course for you as well, on the subject of engine bearings. This is an original article from Clevite that discusses bearings and bearing clearances in depth. It's excellent reading. Click here for a .pdf of the article. April 15, 2008
Everything that you wanted to
know about race engines but
There isn't a universal set of rules that govern all engine building. The following is information that has worked successfully and should be considered when building a performance engine. A high performance race engine, by its definition, indicates that limits are going to be pushed. The limit that is of most concern, as far as pistons are concerned, is peak operating cylinder pressure. Maximizing cylinder pressure benefits horsepower and fuel economy. Considering the potential benefit, owners of non-race engines, from motorhomes to street rods, also look to increasing cylinder pressure. Increasing the compression ratio is one sure way of increasing cylinder pressure but its not the only way. Camshaft selection, carburetion, nitrous and supercharging can all alter cylinder pressures dramatically. Excessive cylinder pressure will encourage engine destroying detonation with no piston immune to its effects. The goal of performance engine builders should be to build their products with as much detonation resistance as possible. An important first step is to set the assembled quench distance to .035". The quench distance is the compressed thickness of the head gasket plus the deck height, (the distance your piston is down in the bore). If your piston height, (not dome height), is above the block deck, subtract the overage from the gasket thickness to get a true assembled quench distance. The quench area is the flat part of the piston that would contact a similar flat area on the cylinder head if you had .000" assembled quench height. In a running engine, the .035" quench decreases to a close collision between the piston and cylinder head. The shock wave from the close collision drives air at high velocity through the combustion chamber. This movement tends to cool hot spots, average the chamber temperature, reduce detonation and increase power. Take note, on the exhaust cycle, some cooling of the piston occurs due to the closeness to the water cooled head. If you are building an engine with steel rods, tight bearings, tight pistons, modest RPM and automatic transmission, a .035" quench is the minimum practical to run without engine damage. The closer the piston comes to the cylinder head at operating speed, the more turbulence is generated. Turbulence is the main means of reducing detonation. Unfortunately, the operating quench height varies in an engine as RPM and temperature change. If aluminum rods, loose pistons, (they rock and hit the head), and over 6000 RPM operation is anticipated, a static clearance of .055" could be required. A running quench height in excess of .060" will forfeit the benefits of the quench head design and can cause severe detonation. The suggested .035" static quench height is recommended as a good usable dimension for stock rod engines up to 6500 RPM. Above 6500 RPM rod selection becomes important. Since it is the close collision between the piston and the cylinder head that reduces the prospect of detonation, never add a shim or head gasket to lower compression on a quench head engine. If you have 10:1 with a proper quench and then add an extra .040" gasket to give 9.5:1 and .080" quench, you will create more ping at 9.5:1 than you had at 10:1. The suitable way to lower the compression is to use a dish piston. Dish (reverse combustion chamber), pistons are designed for maximum quench, (sometimes called squish), area. Having part of the combustion chamber in the piston improves the shape of the chamber and flame travel. High performance motors will see some detonation, which leads to pre-ignition. Detonation occurs at five to ten degrees after top-dead-center. Pre-ignition occurs before top-dead-center. Detonation damages your engine with impact loads and excessive heat. The excessive heat part of detonation is what causes pre-ignition. Overheated combustion chamber parts start acting as glow plugs. Pre-ignition induces extremely rapid combustion and welding temperatures melt down is only seconds away! For a successful performance engine, use a compression ratio and cam combination to keep your cylinder pressure in line with the fuel you are going to use. Drop compression for continuous load operation, such as motorhomes and heavy trucks, to around 8.5:1. Run a cool engine with lots of radiator capacity. Consider propylene glycol coolant and low temperature thermostats. Reduce total ignition advance 2 to 4 degrees. A setting that gives a good HP reading on a 5 second Dyno run is usually too advanced for continuous load applications. Normally aspirated Drag Race engines have been built with high RPM spark retard. The retard is used to counter the effect of increased flame travel speed with increased engine heat. "Seat of the pants" spark adjustment at low RPM will almost always cause detonation in mid to high compression engines once they are rung out and start making serious horsepower. Set spark advance to make best quarter mile speed not best ET, usually 34 degrees total advanced timing. Top Ring End Gap is often a major player when it comes to piston problems. Top ring butting under high load and heat conditions can destroy the piston top land. Most top land damage on race pistons appears to lift into the combustion chamber. The reason is that the top ring ends butt and stick tight at top-dead-center. Crank rotation pulls the piston down the cylinder while leaving at least part of the ring and top land at top-dead. Actual end gap will vary depending on the engine heat load. Lean mixture, excessive spark advance, high compression, low capacity cooling system, detonation and high HP per cubic inch all combine to increase an engine's heat load. Most new generation pistons incorporate the top compression ring high on the piston. The high ring location cools the piston top more effectively, reduces detonation and smog, and increases horsepower. If detonation or other excess heat situations develop, a top ring end gap set to the close side will quickly butt, with piston and cylinder damage to follow immediately. High location rings require extra end gap because they stop at a higher temperature portion of the cylinder at top-dead-center and they have less shielding from the heat of combustion. At top-dead-center the ring is above the cylinder water jacket. If a ring end gap is measured on the high side, you improve detonation tolerance in two ways. One, the engine will run longer under detonation before rings butt. Two, some leak down appears to benefit oil control by clearing the oil rings of oil build up. Clean, open oil rings are necessary to prevent from reaching the combustion chamber, which is also why some do not like gapless rings. A very small amount of chamber oil will cause detonation and produce significant horsepower loss. Top ring gaps can be increased 50% with hypereutectic pistons. Ring Options of 1/16" or stock 5/64" are offered on most performance pistons. The 1/16" option reduces friction slightly and seals better above 6,500 RPM, while being considerably more expensive. Stock, (usually 5/64" compression rings), work well and help with the budget. Piston to Bore Clearance for hypereutectic pistons were Dyno tested at wide open throttle with .0015", .0020", .0035" and .0045" piston to bore clearance. After 7-1/2 hours the pistons were examined and they all looked as new, except the tops had normal deposit color. Even with 320 degrees Fahrenheit oil temperature, the inside of the piston remained shiny silver and completely clean. Excessive clearance has been shown to be safe with hypereutectic pistons. Loose Hypereutectic pistons over .0020" do make noise. As they get up to temperature they still make noise because they have very restricted expansion rate and do not swell up in the bore. The Hypereutectic alloy not only expands 15% less, it insulates the skirts from combustion chamber heat. If the skirt stays cool piston expansion is drastically reduced. Running close clearances is beneficial to piston ring seal and ring life. A small short term HP improvement can be had by running additional piston clearance because friction is reduced. To obtain actual piston diameter, measure the piston from skirt to skirt level with the balance pad. Pin Oiling should be done at pin installation, whether it is pressed or full floating, pre-lube the piston pin hole with oil or liquid pre-lube, never use a grease. If you are using a pressed pin rod be sure to discard spiral pin retainers. A smooth honed pin bored surface with a reliable oil supply is necessary to control piston expansion. A dry pin bore will add heat to the piston rather than remove heat. Pistons are designed to run with a hot top surface, and cool skirts and pin bores. High temperature at the pin bore will quickly cause a piston to grow to the point of seizure in the cylinder. Marine Applications require an extra .001"-.003" clearance because of the possible combination of high load operation and cold water to the block. A cold block with hot pistons is what dictates the need for extra marine clearance. "Compression Ratio" as a term sounds very descriptive. However, compression ratio by itself is like torque without RPM or tire diameter without a tread with. Compression ratio is only useful when other factors accompany it. Compression pressure is what the engine actually sees. High compression pressure increases the tendency toward detonation, while low compression pressure reduces performance and economy. Compression pressure varies in an engine every time the throttle is moved. Valve size, engine RPM, cylinder head, manifold and cam design, carburetor size, altitude, fuel, engine and air temperature and compression ratio all combine to determine compression pressure. Supercharging and turbo-charging can drastically alter compression pressures. The goal of most performance engine designs is to utilize the highest possible compression pressure without causing detonation or a detonation related failure. A full understanding of the interrelationship between compression ratio, compression pressure, and detonation is essential if engine performance is to be optimized. Understanding compression pressure is especially important to the engine builder that builds to a rule book that specifies a fixed compression ratio. The rule book engine may be restricted to a 9:1 ratio but is usually not restricted to a specific compression pressure. Optimized air flow and cam timing can make a 9:1 ratio but is usually not restricted to a specific compression pressure. Optimized air flow and cam timing can make a 9:1 engine act like a 10:1 engine. Restrictor plate or limited size carburetor engines can often run compression ratios impractical for unlimited engines. A 15:1 engine breathing through a restrictor plate may see less compression pressure than an 11:1 unrestricted engine. The restrictor plate reduces the air to the cylinder and limits the compression pressure and lowers the octane requirements of the engine significantly. At one time compression pressure above a true 8:1 was considered impractical. The heat of compression, plus residual cylinder head and piston heat, initiated detonation when 8:1 was exceeded. Some of the 60's 11:1 factory compression ratio engines were 11:1 in ratio but only 8:1 in compression pressure. The pressure was reduced by closing the intake valve late. The late closing, long duration intake caused the engine to back pump the air/fuel mix into the intake manifold at speeds below 4500 RPM. The long intake duration prevented excess compression up to 4500 RPM and improved high RPM operation. Above 4500 RPM detonation was not a serious problem because the air/fuel mix entering the cylinder was in a high state of activity and the high RPM limited cylinder pressure due to the short time available for cylinder filling. Before continuing with theory, a little practical compression information is in order. If you have a 10:1 engine with a proper .040" assembled quench and then add an extra .040" gasket to give 9.5:1 and .080" quench you will usually experience more ping at the new 9.5:1 ratio than you had at 10:1. Non quench engines are the exception to this rule. Some racers make the effort to convert non-quench engines to quench type engines, as with the Mopar Squish Deck Heads. Compression ratios that work are as follows: RACE GAS 12.5:1- Is the highest compression ratio suggested with unrestricted race gas engines. ALCOHOL 15.5:1- Is the highest compression ratio suggested for unrestricted alcohol fuel engines. Satisfactory use of 14:1 - 17:1 compression engines can be made when restrictor plate or small carburetor use is mandated by the race sanctioning. High altitude reduces cylinder pressure so if you only drive at high (above 4500 feet altitude) a 10:1 engine can be substituted for a 9:1 compression engine. General compression rules can be violated but is usually a very special case such as a 600 HP normally aspirated engine in a 1500 lb. street car with a 12:1 compression ratio. The radical cam timing necessary for this level of performance keeps low and medium RPM cylinder pressure fairly low. At high RPM detonation is less of a problem due to chamber turbulence, reduced cylinder fill time, and the fact that you just can't leave the above combination turned on very long without serious non-engine related consequences.
Various piston, cam, valve, chamber and port configurations have been and are currently being tested to optimize engine internal temperatures. Some engines have ceramic exhaust port insulation coatings that allow cooler cylinder head operation while keeping exhaust temperatures elevated for efficient catalytic converter operation. The same ceramic type insulation on a piston top has been quite successful. Ideal piston temperatures in an operating engine would suggest refrigeration during the intake and compression stroke, and incandescence during the combustion and exhaust stroke. The advantage of a hot piston on the power stroke is that less combustion energy is going to be absorbed by the piston. So far, it is not practical to heat and refrigerate a piston 6000 times a minute. However, if the incoming air is not heated by the piston and the piston reflects the heat of combustion, you start to approach ideal conditions. A polished hypereutectic piston will reflect combustion heat back into the combustion process. This reflection, combined with the insulating qualities of the hypereutectic alloy, keeps the heat in the cylinder during the power stroke. A smooth polished piston runs cooler than a non-polished piston, even after combustion deposits have turned both pistons black. A cool, smooth piston will transmit a minimum of heat to the incoming fuel air mix. The Hypereutectic piston gives the racer a real out of the box advantage with smooth diamond turned piston heads. A polish is relatively easy to achieve and does improve the already excellent reflectivity of the hypereutectic piston. If a buffing wheel is used, you will note a gray cast to the finished piston. The gray results from the exposure of the Silicon particles that are dispersed through the piston. Experimental work to reduce piston heating of the incoming fuel mix has been very limited but, in theory, a thin ceramic coating may prove to be beneficial. A thin, smooth coating over a polished piston should still reflect combustion heat while reducing carbon buildup and protecting the piston polish. It is easier for a thin film to change temperature with each engine cycle than it is for the whole piston to do the same. A thin film can be cooled by the first small percentage of inlet fuel mix, allowing the main quantity of fuel mix to remain relatively cool. Tests have shown that polishing the combustion chamber, valves and piston top can increase horsepower and fuel economy by 6%. All this polishing probably sounds counter to the practice of dimpling the combustion chamber. Dimpling has been show to put wet flow back into the air flow and improve combustion. We do not recommend dimpling, but do suggest cutting a small discontinuity close to the valve seat to turbulate wet flow. Some bench flowed cylinder heads encourage fuel separation at the inlet pot. If a small step is added at the valve seat to force the wet flow over the resulting sharp edge, fuel will reenter the air stream and give you the same affect as dimpling only without losing the benefit of a completely polished chamber. As you reduce wet flow you will improve combustion and most likely need to install leaner carburetor jets. Leaner jets compensate for the excess fuel that is available when wet flow is put back into the air/fuel mix. Significant additional horsepower gains can be had with careful attention to cylinder-to-cylinder fuel distribution by allowing all cylinders to be set "just right". Combustion chamber design work has increased steadily the last ten years. Some of the work is mandated by the EPA and some is the result of race engine development. Some of the smog work has actually enhanced race engine development. Combustion chamber science is now more concerned with the effects of swirl, tumbling, shrouding of the valve, quench, flame travel, wet flow and spark location. A combustion chamber shaped dished piston can improve the flame travel in the combustion chamber. A dish allows the flame to travel further and expand more before it is stopped by a metal surface. This rapid flame travel makes it unnecessary to run big spark advance numbers. Ideally, we would like to be able to initiate ignition at top dead center since this would reduce negative torque in the engine that is now cause by spark advance. We are some time away from a practical spark ignition system that will make optimum power with a TDS setting. Some day it will happen. Don't go out and buy dished pistons for your open chamber 454. The advantage in flame travel is more than offset by the low compression ratio this combination yields. Small combustion chambers respond well to dished pistons, especially reversed dome or "D" cups. A 400 small block Chevy can use a 22CC D Cup piston and still have 10.4:1 compression. The trend in modern engine design seems to be smaller combustion chambers with recessed piston tops for more HP per cubic inch. Ignition timing on most installations should be 34 degrees total with full mechanical advance dialed in. More advance may feel better off the line but the engine lays down as the combustion chamber components come up to temperature. At the drag strip set timing for maximum MPH not best ET. Too much spark advance will shorten the life of any performance engine, sometimes drastically. Nitrous oxide can double the horsepower of most engines with less effort and money being spent than any other modification. Even the "smog people" are usually happy, as the nitrous is activated only during full throttle "open loop". A nitrous engine can be built as a stock rebuild or it can be a dedicated effort to maximize the total performance package. As more power is generated, more waste heat, exhaust air flow and combustion pressures push the limits of engine strength. Often more beef is needed in the drive train and tires. All stock factory engines are built with a safety factor when it comes to RPM, HP produced, cylinder pressure, engine cooling, etc. If you are only going to use a 100 HP nitrous setup on a 300 cubic inch or larger engine, built in factory safety factors are probably sufficient. As power output levels are raised engine modifications are usually prudent. The most common mistake made when using nitrous oxide injection concerns ignition timing. A normally aspirated engine makes its best power when peak cylinder pressures occur between 14 and 18 degrees after TDC. Pistons usually require 34 degrees BTDC ignition timing at full mechanical advance to achieve proper ATDC peak cylinder pressure. The total time from spark flash to the point of peak pressure is typically 48 to 52 degrees. If an engine is producing 30% of its power from nitrous, the maximum cylinder pressure will occur too close to TDC to avoid run away to detonation. If ignition does not get retarded, good-bye horsepower and head gaskets. The key to getting max HP from a max nitrous engine is to shift the maximum cylinder pressure event progressively further after TDC. Cylinder pressure of 1000 PSI at TDC, (FIG. 1), can drop to 500 PSI with less than 3/8" of piston travel, (FIG. 2). If you can manage to get 1000 PSI in the same engine after the 3/8" travel, (FIG. 3), the pistons will have to travel an additional 3/4" to lower the cylinder pressure to 500 PSI, (FIG. 4). Work is defined as a force times distance. An average pressure, (750 PSI X 12-1/2 sq. in.), times distance in feet, (3/8" divided by 12), equals 293 foot pounds of work. Our second example, because it has twice the chamber volume above the piston location, must move twice as far to lower the cylinder pressure by 1/2. Since all the other numbers, by our own definition are the same, the force multiplied by a distance twice that of the first example will equal twice the work done, 586 foot pounds of work. There is no free lunch in horsepower equations because to get 1000 PSI above the piston in the second example takes twice as much fuel and energy as the 1000 PSI in the first example. What this offsetting of the peak pressure does is allow us to use the extra fuel mix available to a nitrous engine without breaking and melting things. The system that allows us to postpone maximum cylinder pressure is ignition timing retard. To a lessor extent short rod ratios, lower compression ratios, high RPM, aluminum heads, a tight quench, a rich fuel mixture, a small carburetor and hotter cams tend to delay maximum cylinder pressure. Understand that, in the quest to delay cylinder pressure's peak time, more is not necessarily better. Instead, consider that the ideal cylinder pressure would be just short of detonation pressure and this pressure would be maintained from top dead center, and as long as possible after TDC. If timing is really late, you won't build enough cylinder pressure to start the car, let alone drive it. The 1000 PSI pressure in the example is not the maximum allowable combustion pressure but, rather, a comfortable pressure for illustration of the work principle. Some nitrous manufacturers recommend, "retard the timing two degrees for each fifty horse power of nitrous". Other nitrous kits have the flame speed artificially slowed by the intentional use of a rich fuel to nitrous ratio. The maximum performance engine with a heavy nitrous load must achieve peak cylinder pressures, with the combustion chamber size being drastically increased due to the piston being on its way toward bottom dead center. The strongest engines have less compression ratio, less spark advance, and more nitrous. Many people just don't like the idea of any retard. They say, "retard timing and exhaust heat goes up". It usually does in a stock non-nitrous engine because lower peak cylinder pressure slows the burning. If the timing is retarded in a non-nitrous engine, the exhaust opens before the fuel mix is finished burning and exhaust temperatures go up. Piston temperatures usually go down and exhaust valve temperature goes up. In the nitrous engine, exhaust temperature goes up for several reasons. The first is that the power output has gone up considerably. More power usually produces more waste heat. Second, the need to keep maximum cylinder pressures within reason has dictated that the biggest part of the fire happens closer to the exhaust valve opening time. There just isn't enough piston travel to extract all the energy out of the charge before the exhaust valve opens. Now, we could and sometimes do, open the exhaust valve later so more combustion pressure energy can be used to turn the crank. The trade off is negative torque on the exhaust stroke. If we still have significant cylinder pressure in the cylinder as the piston moves from BDC to TDC on the exhaust stroke, your net HP falls drastically. A real problem at higher RPM. You can improve maximum power stroke efficiency and minimize exhaust pumping losses by running the engine at lower RPM and/or improving the exhaust valve size, lift and port design. A big nitrous engine likes everything about the exhaust to be big. If it flows good enough the cylinder will blow down by bottom dead center, even at high RPM with relatively mild exhaust valve timing. There are many variables in the design and development of an all out nitrous engine. A mistake will cause the melt down of any piston. The high strength of the hypereutectic piston will withstand detonation and severe abuse. Unfortunately, all pistons, even forged will melt and when cylinder pressure limits are exceeded, run away detonation can occur. The excess detonation heat makes the plugs, valves and pistons so hot the ignition system alone cannot be used to shut the engine down. Continued operation worsens the situation to the point of a total melt down. Designing a maximum performance nitrous engine is more of an exercise in heat management than it is in engine building. Serious nitrous users should review ceramic coatings. A lack of a sufficient fuel supply is probably the most common killer of the nitrous engine. If you add a 300 HP kit to your present 300 HP engine, your fuel requirements roughly double and a shortage doesn't just slow you down, it melts things. An electric fuel pump and fuel line devoted entirely to the nitrous equipment is recommended. If you are using a diaphragm mechanical pump to supply fuel to the carburetor, it is worth while to increase the fuel line I.D. If the carburetor goes lean while the nitrous is on, the pistons can melt even with a rich fuel line trick (1/2" dia.) only makes a major improvement in the operation of diaphragm mechanical pump is not recommended and does not do well at high engine RPM. A large size line is effective with a mechanical pump, even if you use smaller fittings at the tank, fuel pump and carburetor. The advantage of the 1/2" large line is not related to the steady state flow rate of the line. The advantage relates to the acceleration time and displacement of the pulsating flow common to the mechanical pump. High compression ratios can be used with nitrous but shifting the maximum pressure after top dead center becomes more and more difficult. I prefer to use street compression ratios and then just work with adding more nitrous to get desired horsepower levels. When choosing piston rings for an engine the most important factor is the intended use of the vehicle. A piston ring set that delivers excellent street performance may not be correct for an engine that will see competitive action, or for one that will be used with nitrous oxide. Piston rings serve two purposes - to contain the cylinder pressure, and to prevent oil from getting into the combustion chamber. Sealing against pressure leakage, or "blow by", is the responsibility of the top ring. The keys to good ring sealing are cylinder wall finish and piston ring groove condition. If pressure gets past the top ring it is already "lost". Any such leakage will not be ignited by the spark plug, and is unlikely to produce any significant power, even if captured between the first and second ring. The second ring is primarily an oil control device. If the top ring is doing the job, the second ring will see fairly limited combustion pressure. Some companies sell second rings that use complex or fragile designs for sealing. These are prone to premature wear and have unpredictable behavior at high RPM levels. Cylinder leakage test percentages are only useful for comparison to data generated when an engine was fresh. Unfortunately this kind of information can be misrepresented to show very low leakage numbers by folks trying to sell "trick" parts. Leakage tests are steady state - they do not account for time, piston movement, or true operating pressures. "Blow-by" measurement will give a better picture of ring condition, but on track performance is the only real measurement of success. Moly rings are intended for applications where cost is of prime importance. Engines being built for serious competition will be far better off using Plasma Moly ring sets. These feature an extremely durable ductile iron top ring with Plasma Moly facing. This design allows the ring to seat quickly and to maintain its sealing integrity under the severe stress of racing. The second ring is a special low tension plain iron design. These taper faced rings are specifically designed to break in quickly and to keep oil from migrating into the combustion chamber. The SS50U stainless steel oil control rings are the absolute best in the high performance industry. This ring combination gives dependable sealing and allows maximum power production. RING TENSION Piston ring sets are available with either standard or low tension oil rings. The standard tension rings are recommended for street driven applications, and for race vehicles which may see frequent open to closed throttle transitions in use - such as road racing. They are also useful in engines that may experience cylinder bore distortion during operation. Low tension oil rings deliver increased performance due to their reduction in cylinder wall drag. These are highly recommended for many racing applications. Engines using low tension rings should be built with particular attention to cylinder concentricity, and often benefit from the use of a crankcase vacuum system. RING END GAP CLEARANCE The piston ring's end gap can have a significant effect on an engine's horsepower output. Rings are available both in standard gap sets, and in special "file fit" sets. The file fit sets allows the engine builder to tailor the ring end gaps to each individual cylinder. Ring gaps should be set differently dependent upon the vehicles use, within the range of .003" (for the 2nd. ring) to .004" (for the top ring) per inch of cylinder diameter. The more severe the use, the greater the required end gap (assuming the use of similar fuels and induction systems). Engines having low operating temperatures, such as those in marine applications is too small. The chart below is a general guideline for cylinders with a 4.00" bore, adjust the figures to match your engine's cylinder diameter: Top Rings (ductile iron, 4" bore) Supercharged Nitromethane .022 - .024" Alcohol .018 - .020" Gasoline .022 - .024" Normally Aspirated - Gasoline Street, Moderate Performance .016 - .018" Drag Racing, Oval Track .018 - .020" Nitrous Oxide - Street .024 - .026" Nitrous Oxide - Drag .032 - .034" 2nd Rings (plain iron, 4" bore) Supercharged Nitromethane .014 - .016" Alcohol .012 - .014" Gasoline .012 - .014" Normally Aspirated - Gasoline Street, Moderate Performance .010 - .012" Oval Track .012 - .014" Pro Stock, Comp. .012 - .014" Nitrous Oxide - Street .018 - .020" Nitrous Oxide - Drag .024 - .026" CYLINDER WALL FINISH When installing new rings, the single greatest concern is the cylinder wall condition and finish. If the cylinders are not properly prepared, the rings will not be able to perform as designed. The use of a torque plate, head gasket, and corresponding bolts are necessary to simulate the stress that the cylinder head will put on the block. Main bearing caps should also be torqued in place. The correct procedure has three steps. First the cylinder is bored to approximately .003" less than the desired final size. Next it is rough honed within .0005" of the final diameter. Then a finer finish hone is used to produced the desired "plateau" wall texture. Use a 280 - 400 grit stone to finish cylinder walls for Plasma Moly rings. Piston ring grooves are also sealing surfaces, and must be clean, smooth and free of defects. Ring side clearance, measured between the ring and the top of the groove should be between, .001" and .004".
April 2, 2008 Engine Vacuum Should you or shouldn't you race with a vacuum pump ?
If you search hard enough you will find a variety of articles on this subject. It's interesting but not everyone agrees on the same advice. The first question that needs to be answered is; are you racing with a wet sump oil system or a dry sump. If you are racing with a dry sump system, the consensus is fairly clear that a vacuum pimp is the route to take. It will remove the crankcase gases and pressure freeing up restriction and allow the rotating assembly to move in a freer state increasing horsepower. Additionally, as long as you have a pressure relief device either on the pump or in the valve cover to allow air into the system between 12 and 15" of vacuum the wrist pins won't be robbed of the lubrication they require. This is especially beneficial if you race with methanol as it will extract quite a bit of the condensation in the oil allowing you to get more use of the oil between changes.
If you are a racer with a wet sump oil system then here is where the controversy
comes in. The manufacturers of the pumps suggest that a vacuum pump is right for
this application however, not all engine builders agree. Most notably is David
Rehr from Rehr-Morrison Racing Engines. His theory is that for bracket racers
with wet sump systems that any potential horsepower advantage is outweighed by
the decrease in potential reliability. His theory is that the positive crankcase
pressure above that extracted from a header evacuation system helps force oil
into and up the oil pump pickup extending engine and bearing life. From personal
experience, the only drawback is if some oil makes it into the headers which
creates a white plum of smoke. This can be cured however with valve cover
baffles and/or an air-oil separator. Here is the link to
David Rehr's article which I guarantee
is excellent reading and food for thought.
The only problem I encountered was the vacuum created by the headers on the top end of a quarter mile run would still pull a little oil mist through the headers that would burn and create white smoke. This is how I cured that problem. The separator comes with honeycomb style foam inserts that are designed to break the liquids from the vapors. They do a good job of this making the liquids fall to the bottom of the tank however, they don't keep the vacuum from drawing some of the mist up into the headers.
The photo on the right is the top of the separator with the foam installed and the cap off. |
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One
of the last details in preparing a new motor is of course installing a new
set of spark plugs. When running a high compression motor like I do, it's
imperative to index the plugs. If you have never done this, what indexing
means, is that you always want to be sure the open spark gap between the
electrode tip and the ground starp is facing down towards the center of the
chamber. By doing this, you accomplish two things. First, this drastically
reduces the chances of the piston hitting the ground strap of the plug
destroying it and secondly, you increase the efficiency of the motor by
igniting the fuel and starting the burn in the center of the chamber
allowing the flame to travel the path as designed into the pistons and
chambers of the heads. It's pretty simple, the greater the efficiency, more
horsepower with less fuel.
As
I mentioned on the Home Page, I really wanted to know what my car is going
to run with the changes. I already had
In
the back of the July 25th edition of National Dragster, Bruce Deveau writes
an excellent column regarding winning and losing and how much of it is
dealing with attributions. The bottom line is that you must take
responsibility or ownership for the reason you lost. Don't blame anyone or
anything else for your losing, accept the responsibility that you screwed
up. Then you must deal with the analysis of what you did wrong and how you
are going to correct it. Bruce is a psychotherapist, mental skills coach and
author of The Racer's Mind. If you haven't yet, read the article.
Internal
problems can occur in your engine that leave tell tale signs. If you act on
these tell tales signs soon enough you can save yourself thousands of
dollars. One of the things that is so important is to inspect the oil and
oil filter when you change the oil. I noticed my problem when I had specs of
bearing material in the bottom of my oil filter. I use a billet aluminum,
washable, re-useable TruFilter TFL-35 oil filter on my car. Yes, it costs
$179 but it's the last oil filter I'll ever have to buy.
Lab
tests have proven that 40 micron particles are the most damaging to your
engine and paper filters can even come close to that.
By
now, your plate is as smooth as glass, well almost. The final step is to rub
the surface with Mother's Billet Metal Polish. You need to do the entire
surface a quarter at a time at least twice all over. Apply with a soft cloth
using your finger and really work it in. Then wipe clean with a paper towel.
By the second polish, your plate will be very bright and have a mirror
shine. I have found that using the Mother's product it best for the initial
work but
Some
engine builders have resorted to "modifying" thrust bearings when all else
fails to cure a thrust bearing problem. One simple modification that can be
made to the upper thrust bearing to improve lubrication is to file more
chamfer (approximately .040˝ or 1 mm) on the inside diameter edge of the
bearing parting line.
The
oil accumulator at the left is a 1-1/2 quart Moroso P/N 23901. Stef's and a
couple other manufacturers make them as well but I'm intimately familiar
with this one. The concept is that when or just before you start the motor,
you send a 1-1/2 quart squirt of oil through the bearings so that you don't
start it dry. When the oil pressure exceeds the pressure in the top of the
unit, the excess oil is forced into the unit where it stays until the unit
is either closed or the oil pressure drops below the pressure in the top of
the unit. This guarantees that you will always have at least some oil
pressure in the motor. This can come in handy as you brake from burnouts,
brake at the top end or if something breaks. I can tell you that on more
than one occasion when I had damage, an accumulator kept the damage from
being catastrophic.
compressed
air. Then install an oil filter adapter similar to a Moroso 23690 (pictured
at the left) between the engine block and your oil filter. The adapter bolts
to the block with the two bolts shown in the picture, then the oil filter
spins on the nipple on the bottom of the adapter. Plumb a single 10 AN oil
line between the adapter and the accumulator.
The
answer to this dilemma is to plumb an electrically operated solenoid such as
the Moroso P/N 23905 (pictured at left) between the ball valve and the oil
filter adapter. If your car is carbureted, I suggest that the solenoid be
wired into the ignition switch so that it opens and squirts the oil into the
motor just before the motor starts and closes when you shut the motor off.
That way it's automatic and you don't forget to do it. You can also wire the
solenoid to another switch to turn it on and off as you choose. 
Piston
temperature and horsepower are interrelated. High horsepower per cubic inch
engines not only make more horsepower but they make more heat. How the
excess heat is handled has a significant effect on total engine power and
longevity.
I went to the local Home Depot and bought a Kohler air filter that was
originally designed for either a lawn mower or generator. It used a 1-1/2" thick
block of filter foam. Out of this foam I cut a doughnut the same size as of of
the honeycomb foam block and insert it into the top of the separator. This foam
filter material would allow air to pass through it but not any
liquid. If it ever becomes soaked it's simple to remove, wash with Simple Green
and replace. This little add on keeps every drop of oil out of the headers
and works well to capture the condensation from the inside the valve covers.