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Help--trying to calculate overbore ring end gap


zigzag240

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I just had my F54 block overbored by .020" for my summer project, I'm putting in some 86.5mm ITC pistons, chrome top rings.

 

I have it back on the stand and I started trying to calculate the ring end gap because is didn't have the shop check it for me. But between the 'How to Modify...' book and the FSM I'm confused.

 

My bore is now 86.5mm or 3.405 inches. Can some kind soul help me calculate the new, proper ring end gap for the top and second ring.....

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I just went through this same issue a few weeks ago. The general concensus was that the ring manufacturer is the one who specs the end gap. Usually it's a function of diameter, for example:

 

gap = .003" per 1 inch of diameter.

 

In my case I was using ITM pistons and rings (not sure if they're related to your ITC) with a top moly ring, not chrome. The manufacturer was no help with end gap, so in the end I went with .014" for the top ring and .012" for the second. FWIW, my N42 was bored .030 over.

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Actually mine are ITM at .020" over, I mistyped ITC, my bad.

 

I just spoke to a tech Winston at ITM, he was friendly but as you said no help...he said they didn't show any end gap specs for them. oh well... thats what makes rebuild so fun..

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