57 548 block technical question

[Mike E.]

I have a chance to buy a 548 block dated February 1957. It mics out as a 265, which I know that Chevrolet did with some of those blocks.
My question:
Is that identical to the 283 548 block? In other words, is there adequate wall thickness to bore to 283?
I can't imagine them having the same casting number for two different blocks, but I want to be darn sure before I go boring into water jackets, etc.
Anyone had first-hand experience with this?
Thanks!

[Theodore K.]

Re: 57 548 block technical question

Mike,
My 283 '57 548 is bored out to 4" which makes it a 302. Works okay. Also, I have had a 307 bored to 4" to make a 327 without problem. I don't recall the diameter for a 265. However, I do remember a caution in one of the books that said some of these blocks did not have good core centering when casting and you could hit a water jacket. Unfortunately, there is only one sure way to know. I would think that boring to a 283 diameter (I think it is 3.875) would be okay.
Ted Von Kampen

[Michael H.]

Re: 57 548 block technical question

Some of the larger engine rebuilders are equipped to do sonic testing which would be an accurate method of determining the thickness and core shift of the cyl. walls. The orig 265 was 3.75 so you would need another .125" to arrive at the 283 dim.

[Robert Willis]

Re: 57 548 block technical question

In 57 Chevy made some 265s that were a 548 casting. Those old blocks will take a healthy over bore and I'm sure they were a 283 block that were finished at 3.750 for a 265 instead of being at 3.875 for a 283. I have saw them advertised before back when I was into 55 to 57 Chevies.

Bob

http://members.kos.net/willisb/

[Mike Cobine]

Re: 57 548 block technical question

That .125 overbore is only a .0625 cut on each side. If the wall is so thin you'd hit water on 60/1000ths, then it isn't a good idea to use anyway. Sonic testing is the only way to be sure, as you could have some thin spots in the casting, but odds are you have a 1/4 inch wall there and .0625 into it won't hurt.

[Edward M.]

Re: 57 548 block technical question

I know a number of Classic Chevy people that have done this with a 57 265 block. They wanted a standard 283 bore, so they bored the 265 block out to 283 specs, then used standard 283 pistons. I would not expect you to have a problem doing this.