The Ford Barn - View Single Post - Sonic tests back-Too thin for 3 5/16 ?

tubman · 05-26-2022, 10:36 AM

I've bored 3 8BA's to 3 5/16". The only problem I ran into was on the last one that had a hidden pit (casting flaw) that we broke into boring the block. It didn't go through to the water jacket, and the machinist said it would be OK as is. For an extra $80, I had him install a sleeve just to make sure.

As to the extra 1/8" being worth it, consider this : A stock (3 3/4") stroke flathead with an 1/8" over bore yields 258 ci. This is 3 ci more than the vaunted Mercury crank provides, with lower piston speeds, and for less that one quarter the price. Sounds like a deal to me.

05-26-2022, 10:36 AM	#17
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,320	Re: Sonic tests back-Too thin for 3 5/16 ? I've bored 3 8BA's to 3 5/16". The only problem I ran into was on the last one that had a hidden pit (casting flaw) that we broke into boring the block. It didn't go through to the water jacket, and the machinist said it would be OK as is. For an extra $80, I had him install a sleeve just to make sure. As to the extra 1/8" being worth it, consider this : A stock (3 3/4") stroke flathead with an 1/8" over bore yields 258 ci. This is 3 ci more than the vaunted Mercury crank provides, with lower piston speeds, and for less that one quarter the price. Sounds like a deal to me.