Thanks. Thats reassuring to know.

If sonic test show no problems the honing and rering should work out fine. I drag raced a 312 bored .112 over = 3.912 bore. I drove this car well over 100,000 miles with no problem. Some have been taken out .125 and ran well.


-Gary Burnette-

Hi. It's definitely an American block, I checked the casting numbers. The bores are worn, but strangely it ran fine and didn't use oil or smoke. It did breath quite heavily when hot though, but I have 3 friends with Y block powered cars and they all do! I thought of ramming a hone down the bores and re re ringing it but that's not the way we do things at our engine shop 😀

If it was running fine maybe a re ring can be done.Is that a Canadian block?I read on here some had a thicker casting in cylinders.Maybe you lucked out.

Oh, cheers for the replies too. I can well see now that sleeving might pose problems. We have sleeved all kinds of blocks without problems so it might be my only way out of this.

Thanks for the welcome. Yeah, we often have custom pistons made , it was an option I had considered . I know some don't recommend boring a Y as large as 80'' even, but this engine has been running fine for the 12 years I have owned it, she popped both head gaskets and the rear seal was leaking so that is the only reason I pulled the motor. Got quite a shock when I looked inside it.

Mike.  Welcome to the site.
 
The problem with sleeving a Y is that the head gasket does not seal fully around the edge of the cylinder.  If the boring operation to install the sleeve breaks into the water jacket, then the potential is there for the water to seep up to the deck at a point that the head gasket is not on the edge of the sleeve and the water then seeps into the combustion chamber.
 
Sonic testing the cylinders will indicate where potential core shift resides and this can give you a better feel for what thickness sleeve you can use or if the block can be sleeved at all.  Assuming the sonic test indicates sufficient material for some additional boring, another option is to use a custom piston.  Pistons can be made to any specific bore size and the only limitation here is making sure you can get a ring set for the selected bore size.  I have seen 312 blocks taken out as far as 3.937” but if they haven’t been sonic checked, core shift can rear its ugly head.

Lorena, Texas (South of Waco)

You should sonic check the cylinder walls to see how much meat you have left.. That will tell you if it is wise to spend time and effort on this block... .

You may be able to find a sleeve with the OD nearly the same size as your current bore, therefore you would only need to make a small cut to bring the cylinder to correct size to fit the sleeve

Hi all. Need some advice please . Just tore down my 312 and found out that it has already been bored 80'' oversize. I didn't even know 80'' pistons were available! The ideal solution would be to find another block but there is nothing available here in the UK. My only option is to sleeve it back to standard, which is not a problem as I work in an engine machine shop. I have been trolling the internet looking for information, and people seem to suggest that the 312 is weak on the cylinder walls, would hate to start boring it out and break through into a water jacket. Has anybody resleeved one before?