Engine Head Stud Heights
 

I am rebuilding a 1974 911 2.7MFI engine. I have put in new time certs. When I screwed in new Dilavar head studs they all stood at 143mm. The project manual state 133/4 mm for Porsche studs. Before I locktite them is this going to be a problem

Unfortunately not answer to your question, but a side note about head stud heights;
I was just putting new head studs for early alu case and measured that new steel head studs from Porsche (so not aftermarket) are app. 2mm longer than factory originals from 50 years ago (same part #). So instead of 135mm, they are 136-137mm when installed

The head stud height is a concern in relation to the barrel nuts at the heads. If the stud length is too long, the stud will come up too far in the nut and push the hex driver out of the nut as you are tightening the nuts. So do a test fit of a cylinder and a head and see how far off your stud length is by installing a head washer and nut.

You could also eliminate this concern altogether by installing a class 10 flange nut with typical hex head instead of the barrel nuts. You want a 15mm hex size to allow use of a socket that will fit into the head.

These nuts might also offer a solution.

FS: 911 Exhaust Barrel (Allen) Nuts, 999.085.001.02, $12.14 each

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