10 Lessons Learned From Engine Masters
by Andy Dunn ©2004
The Engine Masters Challenge is a yearly engine building contest created by Popular Hot Rodding magazine. 50 engine builders attempt to build an engine that produces the highest average horsepower and torque over a given rpm range.
On a dynamometer, you can analyze peak power and torque, or you can analyze average power and torque over a given rpm range; this competition only cares about the "average". Many engine builders and racers worship the false god of "peak". When trying to increase an engines average power, a builder quickly learns that changes with carburetors, headers, and spacers most often only teeter-totter the curve. This alters peak but does not change average. A 408ci engine might have a peak HP of 650 and a peak TQ of 550, but the average total for an rpm range of 2500 to 6500, might be closer to 500HP and 500TQ; these two numbers are added together produce a score of 1,000.
1. HEADS, CAM, COMPRESSION - Cylinder heads, camshaft, and compression, will always be the largest determinants for the final power output of any given engine. More than 95% of an engine's power is derived by the "big three"; this was true in the past, and it will hold true in the future.
2. HEADS - Heads are everything. If you need more power, then you need more air-fuel mixture flowing through the system. When making a bigger explosion, larger quantities of air and fuel must pass through the system. I personally feel that port volume is over-rated and flow is under-rated. Porting must be consistent and efficient, but generally speaking, more flow means more power. Here is a quote from John Kaase, the 2003 and 2004 engine master champion:
"Chris Howe, labored two days on porting and valve seat work. We started the testing with full-size intake ports and later shrunk them down, which made very little difference at any rpm." - Jon Kaase
This is a good example where port volume had negligible effects on flow and power. Kaase's heads outflow the competition, especially at mid-lift. If you have the skills to pull it off, one of the ways to improve flow is to shrink the combustion chamber. This reduces the quench distance and places more of the chamber in the top of the piston. This makes for a very efficient chamber and is referred to by my Phd friends as a "Heron" chamber. This will not help peak flow but does help mid-lift flow numbers since the valves are un-shrouded sooner.
3. CAM - The camshaft determines the shape and size of the horsepower and torque curves. Camshafts are chosen to optimize horsepower and torque for a given rpm range. Drag racing, roundy-round, and road racing, all require power in different areas. Computer simulation software is very good at finding a starting point for picking the cam that will best match your specific power needs.
* Lobe Shape (Lifter Acceleration Rate)
The computer is good at finding the correct duration. Lift is often limited by rules. The lobe shape should be as aggressive as possible, with practical engine life in mind. The lobe shape is probably the part of the cam design that is least understood by the public. The faster you can open and close the valve, the more efficient the system, and the more power you will make. You can design a camshaft with a 280/288 duration and 106 centerline many different ways, based on the many different lobe shapes. Use the computer, talk to the cam reps, and do some testing.
Belt drives are worth the investment because you can test various intake centerlines; wiggling the cam finds power.
4. COMPRESSION - More compression makes more power, assuming you can control detonation. Compression is often limited by rules. In the Engine Masters, contestants are limited by 92 octane pump gas. The most popular compression in the winner's circle is 12.5:1. This ratio is too high for a street car, but it has a place in race engines on the edge. Many builders are scared of compression, it's worthwhile to test and find the engine limits using a research mule.
5. MANIFOLD - If heads, cam, and compression are the "big three", the intake manifold makes the "big four". The manifold is an extension of the cylinder head. Most of the top engine masters test and re-test to find the manifold that best works for their mill.. I don't have statistical proof, but I believe a manifold should flow the same or 5% better than heads at peak. If you have heads that flow 350, I would start testing with a manifold flowing in the 350cfm to 365cfm range. If your manifold flows less than your heads, air flow becomes restricted and total power will be reduced. If your manifold flows way more than your heads, the air gets lazy, loses some velocity, and power declines.
6. CARBURETOR - It surprised me and all the lads at Westech Dyno, when we put an 830cfm on my engine and did a baseline pull, then sleeved it up to 1050cfm, made one jet change and repeated the pulls, and the total average power was identical. Don't get too hung-up on the carburetor. Pay the money ($700 - $1,500) for a good race carburetor, tune it, and don't worry about it; retune it when conditions dictate.
7. HEADERS - I took seven sets of headers to the dyno; I was certain that one pair would have the magic.
* Hooker (2 sets)
* Mac Performance
* Kooks (2 sets)
Once again, me and the lads at Westech Dyno were shocked that all of headers produced average scores within 5 points of each other. The headers had different peak horsepower and torque, but when you examine averages, the truth is revealed.
Most racers and engine builders want headers with primary and collector tube size diameters that are simply too large. My rule of thumb is to choose a header with a primary tube size, ten percent larger than the exhaust valve. Start in this range and test. In the 2004 engine master competition, most heads had 1.6" exhaust valves, and most competitors were running with 1.75" headers.
One of the more interesting tests we did while preparing at the dyno, was to run a set of 1.75" Kook's with a 3" collector VS. a 1.75" to 1.875" stepped Kook's with a merged collector. The difference in scores between the two headers was 1-2 points at best; that is 2 points out of 1,000. I've never been convinced that stepped headers or merged collectors make more power, and this test reinforced my beliefs. The two headers did have differing peak numbers, but peak is the false god...average is the true strength of the engine. Stepped headers and merged collectors are expensive. If merged collectors work, why do they work? It's my belief that they work by simply reducing the size of the collector (people choose collector diameters that are too large).
I wanted to test my size reduction theory; on the fourth day of pulls, with a standard set of 1.75" Hookers with a 3" collector, I mounted a pair of 2.5" collector reducers, inside the collector pipe. These reducers cost $25. We ran the test and picked up 2-3 average points. You can spend $500 on a pair of merged collectors, or you might try testing a cheap pair of collector reducers, fit inside your exhaust pipe. I think you will be pleased with the results.
8. BIG BORE SMALL STOKE VS.. SMALL BORE BIG STROKE - On paper, a big bore with a small stroke makes more power than a small bore with a big stroke. I'm not clear on all the reasons, but I do know that heads flow more efficiently over a bigger bore. When you add detonation to the story, suddenly the small bore big stroke gains the advantage. Kaase was one of the first to use this in competition.
"Because of the low test rpm range, I felt I needed the longest stroke and smallest bore with which the heads would work. With pump gas, detonation was a huge factor in the design of the short-block and heads. A smaller bore has less chance of detonation because it doesn't have some far-off place for a secondary flame front to start." - Jon Kaase
9. OIL - As much as I don't want to believe it, there is hidden power in motor oil. When going from SAE 20w-50, to synthetic 30, and then to synthetic 20, 2-5 average points in power were found. Thin oil makes more power than thick; synthetic oil makes more power than regular. The gains aren't huge but they do exist and they are clearly seen on the dyno runs.
A good oil pan allows oil to drain properly; a bad pan can cost power at certain rpm levels. Too much oil will effect power adversely and most people run with too much oil. Don Terrill suggests testing an 8qt pan with 5qts of oil and I have to agree. On the dyno, my engine master's engine was happiest with 5.5-6qts.
"With a properly located oil pump pickup most engines don't need more than 5qts of oil. Want to see how critical oil level is to power? Test it: If you have an 8qt pan, run it with both 5 and 8."...Don Terrill
Too much oil pressure reduces power. It takes more energy to turn the reciprocating assembly as it slings off excess amounts of oil. Too much pressure can prematurely wear the cam and distributor gears. If you have an engine that won't hold timing, pull the distributor and look at the gear. If the gear is worn, the cause may be excessive oil pressure or an improperly clearances distributor gear and shaft. A good rule of thumb is Terrill's 10lbs of pressure for every 100hp.
10. TESTING - The best way to find the truth is testing. Engines are tested on dynamometers. Book the dyno for longer than you think; one day is barely enough time to break-in an engine and set the carb. Check the oil and water temperature every run and be consistent. Make good notes for every run. Only test one thing at a time. Use average horsepower and torque for your running range as the yardstick to compare changes. Average horsepower and torque are easy to find with SuperFlow software, just click File > Average > Columns and then select the RPM range you want to analyze.