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Registered
Join Date: Dec 2005
Location: Mount Airy, MD
Posts: 4,299
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shimming the cam tray?
I seem to remember, IIRC it was Henry from Supertec, that mentioned in one of his fab motor builds that he used a shim between the cam tray and the heads. This would change the relative angle of the rocker foot to the valve stem, but that angle should be corrected for by the ball seat in the adjuster, right?
If this is correct, how much can one shim? I would assume at some point the interface angle has changed enough to change the valve timing. Thanks a bunch!
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1967 912 with centerlocks… 10 years and still in pieces! |
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12-16-2009, 02:18 PM
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Join Date: May 2003
Posts: 3,346
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Shimming the cam tower will cause the adjuster foot to be offset slightly on the end of the valve. I guess a small offset would not cause problems. Are you lowering the deck height that much? It's common to shave the heads up to 1mm and shave the chain boxes to match. More than that and the chain gets to long. Are you going furthur than 1mm?
-Andy
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72 Carrera RS replica, Spec 911 racer |
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12-16-2009, 02:41 PM
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Join Date: Dec 2005
Location: Mount Airy, MD
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Found it! "Old school with a twist". Supertec used 0.040" and was going to stock 0.060".
Andy: I've been piecing together a 2.8 since I got a ride in 2006... Before I got learned enough to learn 2.8 heads are $10+k, blemished even, if you can find them. So I've chucked an SC head on the lathe and cut the head until I reached the 92 mm diameter of the cylinders. Had to shave 2.1mm. Still have to deal with the stud pattern... But with a 1.5mm (0.060") spacer, that's back in the doable range with stock chains/wheels. |
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12-16-2009, 06:18 PM
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