Recently built an ls6 for my brother's truck. It's an iron block, forged bottom end, -4cc from stock LS6 pistons, 243 heads, i think it was around a 218/220 .563 112 cam, truck intake, ported throttle body, airaid intake, stock exhaust manifolds, gutted cats, flo-pro cat back. I've been tuning it alot and i can't seem to get any power out of it. Could the exh manifolds or intake be holding it back that much? Oh and the tranny was rebuilt with a shift kit and converter replaced (stock) while it was out and i noticed the thing stalls at 1450rpm, is that normal? All my experience is with my 4l80e. It can't even break the tires loose, not even with a brake torque!

 

I would say the manifolds may be holding it backa tad but the main problem I see is the stocl converter.. I would have went with atleast a 3k but someone that knows more may see the problem

 

It's the exhaust.

I sold off my headers and went back to full stock exhaust and man, huge difference, and not in a good way. It lost a lot of low end, and it revs a lot slower than it did before. So in conclusion, I'd say you need some headers on that thing to let it breathe.

 

Humm that's a pretty small cam you should definatly be able to break torque and spin the tires! You can break torque a 6cylender pickup! I'm thinking it's something in the trans. Maybe a bad torque converter... But I'm not a genious just a guess