Originally Posted by slate84
i've read in quite a few forums on 3rdgen.org that the lt1 cam was a good canidate for the lb9 motors. was i missinformed?
Its a cheap way to upgrade from the tini tiny stock LB9 cam.
But like any other cam it needs to be matched to the job. When you increase the cam valve open duration, the intake valve closing point is delayed. To recover the loss of physical compression, the mechanical compression ratio of said engine needs to be increased to restore the cylinder pressure.
Like I said the LT1 cam needs a higher than stock compression ratio.
The LT1 motor is 10:1. the LT4 motor is 10.4:1. Take that as a clue.
Cam timing is aways a compromise. You can fine tune the LT1 cam into your motor by adjusting the cam phasing. Closing the intake valve sooner (cam advanced) creates more low rpm cylinder pressure and torque.
A small Ci motor being short on torque to start with requires critical cam/valve event timing. It all has to work together. If you expect a new camshaft with more duration and or later intake valve closing point, than the old cam, to make more power, the heads have to flow more air and the mechanical compression ratio has to be higher (within limits). The usable rpm range is extended but usually at the cost of some low rpm torque. Needs more gear ratio and a higher stall torque converter. The cam/valve events must also work in sync with the exhaust system (scavegeing). If the exhaust is restrictive (stock puney manifolds/pipes) don;t expect much more power.