Quote:
Originally Posted by Formulajones
And Paul is well aware of the rod issues when it comes to cranks with BBC rod journals and aftermarket rods in these Pontiacs. It's been a problem in the aftermarket for quite some time. That area has been addressed so you guys are going after a dead end there.
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How do you know this has been addressed in this build? Have you been inside this engine? Do you have documentation of the parts used and clearances in question in this engine?
The shop that built the engine may be aware of proper clearances required, but are these clearances DOCUMENTED anywhere for this build? Typically you want at least .060" between the bottom of the piston and the crank counterweight. Autotec pistons want at least .050" side clearance between rod small end and pin boss of piston.
I had to have my aftermarket rods narrowed .045" on the small end to clear my autotec pistons. Eagle 6.8" rods and Scat 4" forged 3" main crank. Mine are BBC rods, and the rod offset isn't perfect when rods are used a Pontiac.
http://racetecpistons.com/media/pdf/...STRUCTIONS.pdf
Hard facts are in short supply in this thread. It's nigh impossible to give good advise unless you know things like dimensions of crank/rod/piston, piston material, compression test readings, all bottom end clearances, etc. All we've got here is a bunch of short youtube vids of a noisy motor and a room full of guys playing 20 questions. (myself included). Questions get raised that don't get run to ground. For example, sometime back there was a picture of very suspect valve adjustment, and several members questioned it. I don't recall seeing an answer or explanation about it. (The questionable poly-lock heights.)
If this was my motor, I would have resolved all valve setting and tuning issues first. Next would be a good compression test. If it continued to make noise and run like crap, it would be out and apart on my stand, while I verify all clearances in conjunction with the builder. Since Joe can't do this himself, he's going to have to have somebody do it for him. I'm sure he doesn't want to, but it's likely got to come out again, unless somebody finds something stupid in-car.
It's a sad state of affairs, because this sort of thing turns new guys off on the car hobby. It's not supposed to be this miserable. But it can be.