lt4 fd

Just curious if a motor, lt1 in this case, that is setup with several induction or intake improvements but stuck with a stock exhaust manifold if advancing the stock cam a couple degrees so the exhasut opens sooner would help any at all or really what would its effects be? Maybe going from a 1.5 to a 1.7 rocker on the exhaust only is a better way to help? Could sticking with the 1.5 intake rocker improve power over going to a larger rocker ratio on the intake when there is a restrictive exhuast? Reason I ask is I am going to have an lt1 that will be stuck with stock manifolds for a while and want to make the most of it for the time being and learn something while im at it. The sole purpose of this car and motor is to learn and tinker, and since the motor is out of the car there is really no easier time than now to do a few things.

blown3rdgen

Since the motor is out of the car, I would call around and get a custom spec'd cam for your application instead of messing with rocker arms. Like you said, there will never be an easier time. You will probably regret it if you don't. Also a cam change is a good way to learn alot

lt4 fd

This is only a temporary setup and I do not want to spend too much on it untill I find/make headers. Thanks for the suggestion though I was really looking for info on how the modifications I was asking about would really effect the performance given the setup I will have.

INTMD8

Well, a mild cam would still show a good improvement over stock with exhaust manifolds.

Fwiw, LT1 cams cannot be degreed with an offset bushing, as it will change the relationship of the optispark to the crankshaft.

arnie

There is a misconception, or at least a difference of belief, as to what the term 'degreeing' really amounts to. To some, it means merely the procedure of checking to determine where the cam timing actually is, in relation to the crank. To others (myself included) it means not only checking the cam to crank timing relationship (to determine a starting point), but the followthrough of bringing/returning the cam to crank relationship to engineering/OEM specs (or altering to a target or predetermined cam/crank relationship) as well. To be objective about it, it really is a fine line that separates the two beliefs.

Changing the LTx cam/crank timing relationship CAN raise issues with the PCM software, and hard parts as well. In the context of THIS thread, by desiring to 'alter' the cam/crank relationship away from OEM specs, the previous sentence applies. If, on the other hand, the intent is to put timing at OEM specs, it, along with the above quote, does not apply.

Rich, I've become pretty predictable, haven't I?

rskrause

Arnie: you are becoming diplomatic??? I wouldn't call THAT predictable!!!

Rich

INTMD8

Agreed, but if you notice I said "cannot be degreed with an offset bushing", which would imply drilling the timing gear and installing an offset bushing.

Obviously the cam timing can be checked, but can only be corrected by replacing the camshaft.

arnie

Actually, the method used (bushing, multi keyway gear, offset key) is/was of little concern to me. It is the outcome I was attempting to focus on. By "degreed" and "corrected", I (now) believe you were implying (and should have been obvious by the flavor of this thread), positioning the cam timing in an advanced state in relation to OEM specs. If that is the case, I initially, at least partially, misunderstood your original post. I am thus compeled to agree with you.

lt4 fd

I didnt even think of that, well I guess thats out... but lets say it was a standard sbc instead of an lt1, would advancing the cam timing to open the exhasut sooner help in a case where the exhaust was overly restrictive or would the fact that it closes that much sooner negate the gains? Also about the rocker question, do you think there is more to gain by upgrading both rockers equally or just adding larger exhaust rockers to help rebalance so the exhaust can keep up or does it not work like that?