Q: My 1977 Trans Am has a 400, TH350 and 3.23
gears. I have recently rebuilt the motor. It has been bored .020 over, and
reassembled with forged pistons, stock crank and rods. The heads are 6X, which
have been milled to get a 9:1 compression ratio. I also used an Edelbrock
Performer intake, Flowtech headers and a stock carb.
The cam is from Comp Cams (270H) and the converter stalls at
220 rpm. Since the heads have nonadjustable rocker arms, I can't get enough
preload on the lifters and I have lots of rocker arm noise.
How do I fix this problem? Do I get longer pushrods? Are
Chevy and Pontiac lifters the same? Can I put adjustable rocker studs on? Please
help! The car runs well, but lacks performance.
Do you think I have the right cam for the setup I'm running?
I would like to run 13.50s in the quarter mile. I plan on getting the heads
ported and changing to 3.73 gears.
A: The 6X heads have screw-in studs, so
they should not be loose or pulling out like press-in studs will when you
replace the valve springs with slightly stronger ones. That scenario would cause
the rockers to become loose and make noise. It's possible, but highly unlikely.
For starters, make sure your pushrods are 9.125 to 9.150
inches long. If they're the 8.715 length, bingo - problem found. But if it's a
Let's take a look at the factory setting, and then what
happens when you mill the heads. Performance is affected because you have robbed
yourself of cam lift and duration. Poly-locks were invented to take advantage of
cam lift and duration. A popular misconception is that the studs must be changed
in order to have adjustable rocker arms. Any rocker arm becomes adjustable
with the addition of poly-locks. It doesn't matter if you have stock bottleneck
3/8 inch studs or 7/16 inch aftermarket units.
What's a poly-lock? It's a hollow nut that's threaded all the
way through. An Allen-head setscrew winds in the top and comes in contact with
the top of the rocker stud.