I have a 68 with ZZ383. I read something about changing the roller rockers to get more lift out of the camshaft. Would this change the idle or sound of the camshaft any? The car runs really good but I would like to have a little more of that lopey muscle car sound. Would anyone recommend this or am I barking up the wrong tree?? Thanks a lot!! P.S. I put a Magnaflow 2 1/2" dual stainless exhuast on and it really made it pretty quiet.

I'm still a rookie at this stuff, but from what I've read changing from say 1.5 to 1.6 rockers will only change your cam duration @50 about 2 degrees. If thats the case I doubt you will really notice a difference in sound. At the cost of about $200 I would think of another way.

I read on a post that a guy said it would change the lift from .509 .528 to something like .543 .563.

Adding lift does make alittle low end torque, but the heads have to be modified to accept the hgher ratio rocker arms.

The pushrod slot in the head has to be lengthen with a Louis tool, all 16 of them, if not already done. Other items to check are the correct springs for the higher lift, along with spring pressure and retainer-to-guide/seal clearance at max lift, no coil bind at max lift, to name a few.

Sometimes, one can get away with murder and change arms without a problem.

Do a "Thumper cam " search. Someone just did that and was please with the additional noise.

Going from 1.5 to 1.6 rockers will increase lift by approximately 0.030" and duration by maybe 2 degrees.

If this was my engine, I would not do that for a couple of reasons. One reason is that GM has built a very torquey engine in the ZZ383 and there is a good reason why they chose this cam and rocker ratio combination. More duration can cause loss of low end torque although I don't know if it would in this case. It is a small change. Increasing lift can cause concerns with valve springs, piston clearance, etc.

Thanks for the comments. Looks like I best leave it alone.

Imho, right you are to leave well enough alone..

Gooood motor to me...

pdq67

Don't do it without changing the springs. The LT4 springs on your Fastburn heads are rated at .525 max lift.

Thanks al ot for everyones help this is a great site. I'm going to get some pics posted as soon as I can. How do you post them?

I have consistently seen HP gains of 9-15 HP when changing to roller rockers.
Friction reduction is one cause, but probably the bigger cause is a more true ratio from a cast rocker compared to a stamped steel one.