Technical Need advice on a flathead block

It seems to be a good block. It had the sleeves removed and was bored for 239 Merc pistons. Question is, can I bore it .030 over or will I need to sleeve it?

 

They can be bored to 3 3/8" as I understand it. My 1950 8 BA is bored to 3 5/16". I run it on the street and it runs at about 165/175 degrees most of the time. Going bigger could get you in trouble...

 

My 49 8BA is .125" over, no overheating, no issues... other than the T-5 I fried.

 

Curious what the current bore size is now. Was this a 221 before?

 

Yes, it was a 221 with the stock sleeves now it's bored to 239 or 3.1875.

 

Here’s an older thread, I didn’t read the whole thing.
https://www.jalopyjournal.com/forum/threads/221-flathead-over-bore-question.7224/

 

I had one bored to 3 3/8 +.030 walls paper thin. 33/8 good grind Merc crank to 4 1/8

 

Bill, if it had sleeves removed and was bored to fit 239 pistons, then another .030" is only .015" per side more. I'd say you'll still have good wall thickness at that diameter. I can't recall what the sleeve thickness was, but Ford put plenty of wall behind those sleeves. Seems like some (or all ) were .083" larger diameter.

 

Chicken above is correct when the tin sleeves are removed the bore was just over .080 larger. Ford offered a set of pistons and rings to put in the block when the sleeves were removed. So the additional bore of .030 over at the now 3 3/16 should work.
Ronnieroadster

 

Thanks for the input guys. For some reason, I was thinking 3 3/16 was max safe bore size. This is good news. I'm going to start looking for some pistons now.

 

Would a sonic? test of the wall thickness be in order?

 

I don't know, might not hurt. I wonder what thickness would be a no-go?