I pulled my engine and have a couple of damaged cylinders,apparently from excessive piston rocking with previous owner.It's casting #385596 that is .030" over currently.If everything checks out o.k. other than a possible sleeve,can this block be taken to 4.250" or are the cylinder walls to thin?I have several books on BBC,some say no more than .060",some say that .155" is fine,as long as there is no core shift.Is this one of the things that I won't know for sure 'til it goes to the machine shop?

I pulled it apart due to water coming out the header collector gasket.Head was cracked above the exhaust seat on #8,looked to be starting on #6.Casting #3846206.I think it may have fell victim of overporting.

You're gonna get a lot of opinions on this one. With anything over .060, you really should have the block sonic tested to make sure there's enough there to keep it together. Some say never go over .060 or .070...I know others who build 454's and go .125 all the time with no problems..It depends who you talk to. If you have it sonic tested, you'll know what you have.

The max is supposidly .125. Sonic testing will confirm if this can be done otherwise it is probably a calculated risk.

http://www.chevelles.com/forums/showthread.php?t=33382

Thanks for the replies and link.

I've talked to the 2 different machinist I use and they both kind of said the same thing,that the older casting 396s tend to have thicker casting at the bore,not all but quite a few.Also said not to rely on casting #s as a guide to the thickness of the metal at the bore,doesn't always pan out.Both said had to check out the block first before they would give any kind of definite answer.

An old rodder's trick was that a 396 could be bored .155" over if an old-fashioned wooden pencil couldn't go between the cylinders through the freezeplug openings!

pdq67

It says that in one of my books also,if that's truly the case I'm good to go,just want to be absolutely sure.Don't really want to spray on a excessively thin cylinder wall.

An old rodder's trick was that a 396 could be bored .155" over if an old-fashioned wooden pencil couldn't go between the cylinders through the freezeplug openings!

pdq67
=
Used to believe this about 35 years ago back before I even knew what sonic testing was,,,
I also installed a number of sleeves,,,, :(

The only way to be sure is to have it sonic tested.

Sure seems easier to me to just find a 454 block.


JIM

Mike said it all........

But I would try the pencil deal first before I started on an old block..

pdq67

I had a 72 402 taken .125 over, and current 74 454 is .100 over, 402 would heat up in traffic, current motor runs 160*