I have a 350 with 4bbl, headers, flat top pistons, decked and planed maybe 10.5 to 1 compression, comp cams 268h cam. (duration 224 int. 230 exh. @ .050) .318 / .320 lift 110 separation) 12 degrees initial advance, 25 degrees mechanical, all in by 3,000. Does anyone have a horsepower / torque calculator. Trying to figure out what RPM peak torque occurs. Looking at diferent gears for this car.
Maybe I need a chassis dyno?! Thanks for any help you can provide.
Chasis dyno would be the way to go. That way you will know exactly where your peak power is and then you can determine your shift points. It might also point out any deficencies you may have in your setup.
Chasis dyno would be the way to go. That way you will know exactly where your peak power is and then you can determine your shift points. It might also point out any deficencies you may have in your setup.
Maybe not. The problem is that most dynos are set up for Chevy motors and the testing software starts at too high an RPM to provide peak torque of a Pontiac. The printouts on my engine started at 3500 rpm and I was already past the peak.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
It will depend on the dyno operator. Most will try to capture the torque peak but sometimes you have to ask for a specific start rpm. Part of the reasoning behind a particular start rpm is that lower rpm poses a problem.
But the question is regarding your gear selection; what ratio are you using now and why are you considering other gears?
Using the hp peak as a shift point is a common fallacy. Having a graph of the hp curve is much more important. The idea is to select the shift point that has the same hp as the recovery rpm (rpm immediately after shifting).
For an example of how this works, suppose you have two engines that have a hp peak of 350 at 5200 rpm. On one, the hp after that point drops quickly, losing 50 hp in the next 500 rpm. On the other, the hp declines very slowly, staying within 10 hp for the next 1000 rpm, then dropping to 320 hp in the next 500 rpm. Should the shift points be at the same rpm for those two engines?
Next: the steps between the transmission ratios also affect the shift points. A wide ratio transmission requires a higher shift rpm than a close ratio transmission.
At the track, I use the dyno sheets and the transmission ratios to determine the best shift points, and use data acquisition to confirm that. The most recent adjustment was a drop in the driver selected 7200 rpm shift point down to a 6900 rpm shift point. It is almost impossible for a racecar driver to "feel" the right shift point as the torque will be dropping as the hp is still rising.
