LS7 - cam/headers/intake - 560 rwhp
10-16-2007, 10:58 AM
#21
Launching!
There have been quite a few LS7s showing RWTQ in the low 500s. Part of the key to this is cam timing vs. compression. The LS7 intake starts to go out-of-tune in the low to mid 6000 RPM range. To get the engine to rev a bit higher, and therefore produce a bigger peak HP number, a lot of cam grinders move the Intake Valve Close point quite late - 50 degrees or so ABDC at .050. The late IVC then bleeds off cylinder pressure (torque) at low to mid RPM - the engine has a low dynamic compression ratio.
Contrast that with the Katech Torquer cam, which has an IVC of about only 36 degrees ABDC @ .050. This results in a (very high) dynamic compression ratio in the low 9s (assuming stock static compression of 11.0). The higher dynamic compression results in more torque, as the name suggests, although the power falls off sooner above 6300 or so, and the peak numbers aren't as high.
If you're trying to have the best of both worlds, you can get close by running a cam with late IVC, but increasing the static compression. The highest HP LS7 builds are often running static compression between 11.5 and 12.
A side note: based on the high dynamic compression people are getting away with, and the fact that some folks see peak HP with timing as low as 24 degrees, the LS7 combustion chamber may be even more efficient than the LS1/2.
Contrast that with the Katech Torquer cam, which has an IVC of about only 36 degrees ABDC @ .050. This results in a (very high) dynamic compression ratio in the low 9s (assuming stock static compression of 11.0). The higher dynamic compression results in more torque, as the name suggests, although the power falls off sooner above 6300 or so, and the peak numbers aren't as high.
If you're trying to have the best of both worlds, you can get close by running a cam with late IVC, but increasing the static compression. The highest HP LS7 builds are often running static compression between 11.5 and 12.
A side note: based on the high dynamic compression people are getting away with, and the fact that some folks see peak HP with timing as low as 24 degrees, the LS7 combustion chamber may be even more efficient than the LS1/2.
