I've been following the discussion related to Chucks engine problem with
interest. My question would be, why does the engine noise related to valve
clearance problems appear only when the engine is under load? Do valves open
further when under a load or at higher RPMs? I don't fully understand the
concept of "coming on to cam" (this may be stated incorrectly) I ask this
because I just put a modified head on my old short block with a "mild" cam.
Don't ask for specs, the po didn't "remember" what cam he put in. I have a
distinct rattle at 2800-3000 rpms. It sounds like valve gear problems to me.
The rattle seems to go away at RPMs above that, although I may not be hearing
it because of the exhaust racket. I can't duplicate the rattle with the car
sitting still, and it barely perceptable when I drive with the top down. I had
milled the head (only to 9.5:1). I bought PI spec push rods anticipating that
the stock US spec rods would be too long. It turns out that the PI rods are
way too short, so I stayed with the stock push rods. I still have a little
room for adjustment. I bought double valve springs, and I don't see any
potential for binding. The lifter clearances are normal, and the rocker
geometry looks good. The rattle sounds like valve lash to me. Otherwise, the
car runs great. How can I diagnose? Joe Davis
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