Joe:
This was not my understanding (although the description was not
precise enough to be certain, so I could be full of hooey).
My understanding was that the noise occurred after two minutes,
independent of load. My carefully reasoned wild guess was that it was
thermally dependant. I.e. the motor warms up, and starts making racket.
He did mention that the motor was noisy when he was breaking in the cam.
Here is a recap of the mods (not all of them were in his original note):
Head milled to 3.3 inches (About 11:1 Compression ratio)
Copper head gasket
1.55 ratio rockers
0.293 lift cam (0.454 total lift) Don't know the duration.
Block decked (how much??)
So his compression ratio is well over 11:1. With
a decked block and a copper head gasket, he almost no piston to
head clearance. With that cam and rockers and milled head, he has
almost no piston to valve clearance, and depending on the springs
he is using, he may not have any valve spring coil clearance. He is
running tubular pushrods, and depending on the length, he may not
have any adjustment left on his rockers.
Chuck: Have I got all this correct?
Anyway, Chuck is out to build one serious motor. Sissies
need not apply. With all that milling, shaving, and special doo-dads,
seems like something is likely to be hitting something else.
That's my guess....
Chuck will set us all straight when he gets the motor
open.
Vance
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Lizirbydavis@cs.com
Sent: Monday, March 22, 2004 10:44 AM
To: 6pack@autox.team.net
Subject: Chuck's problem?
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 P!
I 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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