440 overbore

[chad]

What's the max bore on a 75-78 440 block?. I have a set of .055 over pistons. I can get this block cheap but is it worth it? I am thinking it's a thin wall block from all I have read. It will be a street motor so hard blocking it is out of the question. I have had 2 blocks checked and they were just paper weights Thanks

 

[Mark B]

Can you get it on the condition it will pass sonic inspection? That would be the best way.

 

[chad]

Ya I just wanted to get a general opinion. The guy is a bit of an odd sort. He's kinda hard to deal with.

 

[69Bee]

The idea that the later year blocks are "thin wall" is pretty much a myth. The later blocks usually have larger main webbing than the 60's blocks, and the cylinders are pretty much the same. The biggest concern is the core shift number following the casting number on the side of the block. The higher the number, the greater the possibility that the cylinders could be shifted in the mold.

Your pistons are 0.060" OS, and measure 0.055" because of the bore clearance required for them, and your final bore should be bored and honed to 4.380". As long as you have 0.100" or more of cylinder wall thickess, you should be fine. It will run hotter, but in your location, it shouldn't be much of a concern.

 

[Hemi Rebel]

http://www.440source.com/blockinfo.htm

So, the bottom line? Save and use those late model blocks. And go .060" over with 'em all day long. Also on that note, we know of several machine shops that have been going .060" with late model blocks for over 20 years with no problems.

 

[chad]

That's funny I just finished reading that article. Guess that answers my question.

 

[Meep-Meep]

.040" is the factory spec max overbore but I agree going .060" is rarely and issue, or an non issue on a relatively low power street engine. But when in doubt get the walls sonic checked.

 

[roccodart440]

I went .060 over without issue.