Does boring weaken 500 cylinders?

jseng1 · 2026-05-01T09:47:33-0600

How far can you bore a 500 without having to worry about the cylinders cracking just above the base flange?

johnm · 2026-05-01T15:42:52-0600

My 500 Dommie generator barrels are still going with a 60 thou over bore , 10.25 CR and about 10 years of racing. So 60 thou seems OK.

I have never used sleeved 500 barrels but a fellow competitor told me his failed at the thin area above the studs when he sleeved and raced 500 barrels. He ended up casting new ones in NZ because at that time they were impossible to find. Casting in cast iron.

jseng1 · 2026-05-02T11:22:38-0600

johnm said:
My 500 Dommie generator barrels are still going with a 60 thou over bore , 10.25 CR and about 10 years of racing. So 60 thou seems OK.

I have never used sleeved 500 barrels but a fellow competitor told me his failed at the thin area above the studs when he sleeved and raced 500 barrels. He ended up casting new ones in NZ because at that time they were impossible to find. Casting in cast iron.

This is exactly what I was worried about. I'm currently talkiing someone out of sleeving his cylinders. Personally I had 750 cylinders crack above the base flange when bored to .060" over.

He's putting in these 174 gram pistons:

johnm · 2026-05-02T16:12:31-0600

I think its almost impossible to get liners in with breaking through the casting at some point.

Maybe if they converted it to through bolting??

Never done it myself but one of our competitors did through bolt a 500

jseng1 · 2026-05-02T20:26:49-0600

johnm said:
I think its almost impossible to get liners in with breaking through the casting at some point.

Maybe if they converted it to through bolting??

Never done it myself but one of our competitors did through bolt a 500

Maybe you're talking about Rogers 57hp short stroke 500 w JS ultralight carrillo rods & lightweight pistons. See his shortened bolt through cylinders below.

Does boring weaken 500 cylinders?

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