what kind of power would this combo make with a carb,(650cfm correct?) edelbrock performer manifold and 1.6rr's

Not much after the valve spring retainers are done munching on the valve guides.

A standard LT4 cam would fit. It's the LT4HOT cam that has too much lift, for the stock L31(Vortec) heads.

From the "Camshaft" tech article linked from the thirdgen.org homepage:

1.5:1 Lift------1.6:1 Lift-------Notes
.492/.492-----.525/.525-------LT4 motor cam

That's too much for stock Vortec heads with 1.5:1 rockers, let alone 1.6:1.

But those are the HOT cam specs, not the standard LT4 cam, which is (and a LT1 for comparison)...

Engine Valve Lift @ .050"
LT1 Intake .447"(11.35mm)
Exhaust .459"(11.66mm)

LT4 Intake .476"(12.09mm)
Exhaust .479"(12.17mm)


Engine Duration @ .050"
LT1 Intake 205 deg.
Exhaust 207 deg.
LT4 Intake 203 deg.
Exhaust 210 deg.

.476 & .479 are do-able. The max, but do-able. If you tear them apart, and blueprint the springs, you can break .500, but people rarely go to the trouble.

The .476/.479 numbers are INCLUDING the STOCK 1.6:1 roller rockers on the LT4 engine. It has VERY SIMILAR lift to the LT1 cam.

First you say 1.6 will give you too much lift, .525.

Then you say 1.6 gives .476/479...

I never said that, re-read what I said. 1.6 rockers with a PRODUCTION LT4 cam gives .476/.479" lift. 1.5 rockers gives .446/.449 or VERY similar to the LT1 cam. The HOTCAM has .492/.492" lift with 1.5 rockers and .525/.525" lift with 1.6 rockers.

My bad...I was still thinking your first #s, were the standard LT4 cam, with 1.6, not the HOT cam.

But, I think we both agree, right? That the LT4 cam, not HOT cam, would do well on a L31.

Of course, just spend a few more bucks and get the press-in studs replaced with screw-ins, upgraded springs, a little machine work to the bosses, and even the LT4HOT cam is no longer a problem. By the upgraded heads, and your cheaper in the long ru, rather than redoing it later.