Originally Posted by
beto 
man, not to be mean but search, theres a lot of info in here, just search for it!
Ok this suck !The guys want help and he ask I think it's the reason for forum.
So here what i've found : Cam Tuning
With the mandated 15:1 horsepower-to-weight ratio, torque is the name of the game. 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.
Designed 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.
By playing with cam timing, we hoped for increased performance in the upper rpm. We procured a set of anodized, adjustable billet SR20DE cam gears from Stillen to do just that.
Cam 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. 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. 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.
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. 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 the Clark Steppler magic tune, our Dynojet read 148 hp and 144 lb-ft of torque. Not exactly what we hoped for.
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. We were successful.
Putting the cams straight up, we got 151 hp and 141 lb-ft of torque. 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. 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.
The best horsepower numbers were often matched to the best torque figures as well.
The engine was happy with 2 degrees advance on the intake. While we were happy with the horsepower and torque numbers, power was still nosing off heavily at 6200 rpm. We returned our attention to the exhaust cam. With the intake cam advanced, the engine was highly sensitive to having the exhaust cam retarded, thereby increasing overlap. We got our top end, but with huge penalties in horsepower and torque before 6200 rpm. For a street engine, having an extra 13 lb-ft of torque at 3500 rpm is worth a softer top end.
Spending as much time as we do on the racetrack in the last 1000 rpm before redline meant having to make that tradeoff.
We moved the exhaust back to .5 degrees retarded, hoping to fall somewhere in the middle of good midrange and top end. Exhaustive testing complete, we bolted on our race dump pipe for the big number. Over two points more compression, a slight increase in displacement, and much dyno time yielded us a whopping 3 more hp and 3 lb-ft of torque more than our stock cam timing, stock compression engine.
This could be a function of a crescent wrench I left in a cylinder bore or coagulated knuckle blood on bearing surfaces. Your mileage may vary. The moral? A box-stock roller SR20 is one kick-ass engine, can be yours for about $400, and with just a few bits from the wizards at JWT, is a torquey wonder for your street or racecar. Or you can try to build an engine.
So halfway through the season, we have blown engine number two, and harbor an enthusiasm deficit. Like a phoenix, however, the #27 will rise from its head gasket ashes--with a stock compression engine, upgraded cooling system, weaknesses addressed, all while keepin' it cheap, keepin' it real.
has anyone experience with adjustable cam gears?
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