Quote:
Originally Posted by TomC750
Well, hard for me to believe I did any harm. The tap went in smooth and easy until it got past the reach of the bolt, then there was rust. I have forgotten my "class of threads", but I would expect the bolts to be in that class that allows for a close fit. We rebuilt a lot of flatheads back in the day, I never recall having a leak problem.
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Tubman, threads are cut to a different standard than normal? What standard? They certainly are not AN or NS bolts as used in aircraft or they would be marked as such. I have been reviewing my Engineering Handbook and measuring major diameter, pitch diameter, etc. on the bolt threads as well as the block. This suggests that the threads in the block are class 2 or 3, and the easier to measure bolts are 3. In any case mine are well within spec. Interestingly, a new grade 8 nut is a looser fit on a headbolt than the headbolt in the block.
In another publication, "Best Shop Practices" it states "that when rebuilding assemblies it is important to use an appropriate tap to clean any debris out of the threads. Any other method may imbed particles in the threads and influence torque values." Case closed.