Hi guys help me out. I had a 331 caddy block bored out to 4.000 dia. 365 cc, But it broke thru the water jackets in the bottom of the bore.I was told i can bore these out to 4.250 dia. whats up ? Do i have a very early block or something? Its too thin for sleeves.
Anyone who told you you can bore a 331 to 4 1/4 is dangerous jerk. When they were new we went to 4 inches. A 4 by 4 Cad was 400 inches, a giant motor in my youth. Yours rusted out at the bottom of the water jackets. Are you sure you can't sleeve it? I had a GMC fall through and saved it with a sleeve.
What idiot machinist starts cutting without sonic checking first???? Geeesh Find a new machine shop and ask about sleeves, but you will likely need eight. Is the block worth $800?? .
You could probably sleeve it and pour an inch or two of hard block in it. It hasn't been honed yet, I would think. Who would bore it without sonic checking. Somebody without a sonic checker. Which is almost everybody.
I had the same problem with #8 on my 331 after boring it to 4". every other place in the bores had plenty of meat. we sleeved it and went on with our bidness. just chocked it up to a core shift.
I have never done it myself, I have heard of those blocks being safely bored to a max of 3/16"(4.0"). The reason you can bore them that far is because they were not made with the same precision as later blocks, That same lack of precision means that some blocks will tolerate what others won't. I wouldn't consider boring one 3/16" without first thoroughly sonic checking how much material is there. Even if it doesn't break through you could end up with a scary thin cylinder wall. Even if you successfully sleeve it, that's not as good as an uncompromised block. If I wanted a significant displacement in that engine family I would just start with a 365 or 390.
Had one bored 3/16's years ago and ran it for years on the street. Ran it in my 55 Nomad. Had no luck with small blocks even back then. Guess I got lucky.
Starting with a 365 or 390 is a great idea........but your transmission options greatly diminish when you get away from the extended bell of the earlier Cadillacs.
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