![]() Spending as much time as we do on the racetrack in the last 1000 rpm before redline meant having to make that tradeoff. For a street engine, having an extra 13 lb-ft of torque at 3500 rpm is worth a softer top end. We got our top end, but with huge penalties in horsepower and torque before 6200 rpm. With the intake cam advanced, the engine was highly sensitive to having the exhaust cam retarded, thereby increasing overlap. We returned our attention to the exhaust cam. While we were happy with the horsepower and torque numbers, power was still nosing off heavily at 6200 rpm. The engine was happy with 2 degrees advance on the intake. The best horsepower numbers were often matched to the best torque figures as well. By advancing the intake cam and opening the intake valves sooner, we saw better torque numbers with minor peak horsepower penalties, but with big roll-off on the top end. Retarding just the exhaust cam yielded both inferior horsepower and torque numbers, so we put the exhaust cam back to zero and moved on to optimize the intake cam. Putting the cams straight up, we got 151 hp and 141 lb-ft of torque. Rushing for our first race, we had advanced the intake cam 1 degree and the exhaust 2 degrees, hoping to get midrange and kill the top-end power a bit. With the Clark Steppler magic tune, our Dynojet read 148 hp and 144 lb-ft of torque. We settled on what we could beg, borrow and steal: a stock cat, midpipe, and rear section tubing with an Edelbrock RPM-series muffler. With many runs to make during business hours, we had to bolt a quieter exhaust on to the car, which would also better approximate what people will run on the street. Once you have the ideal cam adjustment figured out, another option is to buy preadjusted eight-hole cam gears from someone like JWT, which completely eliminates the risk of slippage and is a good idea on racecars where everything tends to go wrong, always. We've seen a cam gear with only four adjustment bolts slip, so we were happy to see six bolts with anti-slip washers on the Stillen units. We procured a set of anodized, adjustable billet SR20DE cam gears from Stillen to do just that.Ĭam tuning on the SR20 is always a pain, requiring removal of the valve cover, but these gears allow easy adjustment with Allen keys once the cover is removed. In the time between receiving our S3 roller cams from JWT and rebuilding our blown-up engine, JWT came out with a set of trick valve springs and titanium retainers that would raise our rev limit.ĭesigned for the stock 6500 rpm rev limit, the roller S3s nose over fairly hard after 6200 rpm, not ideal for road racing, where the engine lives mostly between 5000 rpm and redline.īy playing with cam timing, we hoped for increased performance in the upper rpm. With the mandated 15:1 horsepower-to-weight ratio, torque is the name of the game. Ok this suck !The guys want help and he ask I think it's the reason for forum. Man, not to be mean but search, theres a lot of info in here, just search for it!
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