Is a 340 with a 4.100 bore size at it's max?

I would think so. That's .060" over, which typically for any production block is pushing it.

Yes…and it should have been sonic checked prior to the last build.

Ok cheers guys i'll steer clear

Stock is 4.040. They only recommend a .040 overbore as max. 4.10 would be way over that. I’ve had a .060 over block develop a pinhole. They are pretty thin.

I have one that is .030" over currently and it will need at least 4 sleeves to go any bigger.

But just to clarify the above, there are other Mfr's blocks that will go .125. But even then, sonic testing is recommended

Also... there is nothing wrong with a sleeved block... in fact, some racers prefer sleeved blocks as the walls become thicker.

Except for the cost of creating one!

I have a 340 laying around. I was thinking about making a winter project out of it. Good thing is if it needs any sleeves I can just stay after at work and machine and install them.

Exactly. If I was still in the machine shop business, I'd have already fixed it, lol.

hi

i did a 340 for a friend at 4.100 and it powers his 74 cuda to 12.5 et s ???

been together for 5+ years now , street engine , pump gas , drive anywhere .

no sleeves !

Did you sonic check it? I'm sure there's a bunch running around at .060" over and are just fine. So many variables to consider.
As much as the 440 blocks vary in thickness, I'm sure the small blocks were no different.

I bought a sonic tester for that reason after cracking a cylinder in my first 400 stroker build, the driver side had massive core shift and the cam side of those cylinders were all less than .060 thick
It was so thin sleeves wouldn't seal at the bottom
I sonic test every block now before sending them to the machine shops for work You should too

The sonic testers do have good merit... especially when they show extra thin walls... something then to consider.