The Ford Barn - Math for valve to head clearance?

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Math for valve to head clearance?

Offy heads with valve pockets .425" deep, compressed copper gasket .062" and net lift .361"; the math says I should have valve to head clearance of .126". When I clay I get .090". Have I left something out in my calculations? My valve pocket depth varies; should it be uniform all around or is the pocket cut on an angle? When I clayed I did so at the .425 depth.

Re: Math for valve to head clearance?

Your numbers imply that the top of the valve rises .397" above the surface of the block. Is the top surface of the valve above the block surface when closed?

Re: Math for valve to head clearance?

Quote:

Originally Posted by BillM (Post 324175)

Your numbers imply that the top of the valve rises .397" above the surface of the block. Is the top surface of the valve above the block surface when closed?

Bill, the top section of the valve on the seat I measured does sit above the deck; that explains it! Thanks for responding, Bob

Re: Math for valve to head clearance?

Bob, you told me last week that my email on this subject, were I explained the valve top, above deck dimension, has to be considered, cleared up your math problem and you were now within .008 of an inch??

Has something happened to change your readings?

Re: Math for valve to head clearance?

Quote:

Originally Posted by JWL (Post 324238)

John, we had discussed this very problem and I failed to link what you pointed out to me as to how it would relate to my valve to head clearance. Last night in a very cold garage (excuse) I came up with a net lift of .361" when actually it is .353" as we discussed earlier. The .361" lift worked out perfectly with pencil and paper and gave me the exact answer that coincided with the .090" I got when I measured the alumna pea ( .425" valve pocket depth + .062 gasket - .361" net lift -.036" for valve above the deck.) Now with the correct net lift of .353" I'm back to the missing .008"; you stated that a reground cam could account to up to .004" discrepancy; so that leaves me with for me an unexplained .004" somewhere. As I'm writing this post am going back and forth to the garage & computer to verify my measurements and now have discovered the upper section of the valve sits .040" above the deck. Now with that measurement I don't have the missing .004" that I described above. Thanks for taking an interest in this for me; am a slow learner but will eventually get it. Bob