Hello from Germany

[olddog]

Originally Posted by Max Power

I have a 351W with a roller cam and ported Performer RPM heads that makes 355 rwhp behind a c6 tranny.

So I am now ready to stroke to a 408.

Excuse my using torque in ft-lb rather than N-M. I just don't think in the superior metric units.

If you change nothing other than the stroke. Same intake, heads, cam, headers, etc., your engines torque curve will shift to 351/408 rpm from the present rpm. Your engine will make the same torque only the rpms will be lower when that happens.

for example:
351 rpm -- torque -- 408 rpm
1000 ------ 350 ----- 860
2000 ------ 375 ----- 1720
3000 ------ 400 ----- 2580
4000 ------ 425 ----- 3440
5000 ------ 400 ----- 4300
6000 ------ 375 ----- 5160

If you had a dyno pull chart on your engine it would be helpful. The question is where does the torque start dropping off faster than the rpm is rising (definition of peak hp). The next question is why is the torque dropping rapidly. If it is because the springs are no longer keeping the valves in control at higher rpm, then your stroker will make more Hp (Kw), as it will continue to make more torque up to that rpm. This is true in theory from an air flow point of view. In reality the stroker will make a bit more torque everywhere as the torque curve will shift up a bit from the stroke increase. However this will give you an idea of how your cam would perform.

[Max Power]

Originally Posted by olddog

Excuse my using torque in ft-lb rather than N-M. I just don't think in the superior metric units.

If you change nothing other than the stroke. Same intake, heads, cam, headers, etc., your engines torque curve will shift to 351/408 rpm from the present rpm. Your engine will make the same torque only the rpms will be lower when that happens.

for example:
351 rpm -- torque -- 408 rpm
1000 ------ 350 ----- 860
2000 ------ 375 ----- 1720
3000 ------ 400 ----- 2580
4000 ------ 425 ----- 3440
5000 ------ 400 ----- 4300
6000 ------ 375 ----- 5160

If you had a dyno pull chart on your engine it would be helpful. The question is where does the torque start dropping off faster than the rpm is rising (definition of peak hp). The next question is why is the torque dropping rapidly. If it is because the springs are no longer keeping the valves in control at higher rpm, then your stroker will make more Hp (Kw), as it will continue to make more torque up to that rpm. This is true in theory from an air flow point of view. In reality the stroker will make a bit more torque everywhere as the torque curve will shift up a bit from the stroke increase. However this will give you an idea of how your cam would perform.

Thanks for the reply.

re: metric vs. standard, there are two kinds of countries: those that use the metric system and those that have landed on the moon.

I am an American stranded in europe for the moment so I understand and prefer the standard system.

Here is a dyno pull. I made peak power at nearly 6600+ rpm, which is more rpm than I was ever hoping to spin this motor. the engine masters 408w using the afr 165 heads made 471 hp at 5400 rpm and 515 ft lbs at 3900 rpm. the cam they used was rather small at 218 / 224 dur at .050 and had 513 of lift. What cam could I use that would make my peak power at or below 6200 rpm?