Max bore size on 340 Resto Block

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jimjimjimmy said:
do you know what a 59* r3 will go to on average I know it depends on each block .
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Unfortunately there is NO average from what I have seen. I saw an R3 at another shop that was rough bored to 4.000" and there was a hole in the cylinder! He fought with Ma Mopar for months over it and eventually got it replaced but even still the replacement was found to be incapable of handling much over 4.100" These were non-Siamese as far as I can remember. Moral of the story is each and every one has to be sonic'd and even then the transducer has to be run all over the cylinder to see a "pocket" . Most shops will not be that thorough as it takes time and "jelley" . It's really just a kind of "luck of the draw" kinda situation.

p.s. jimjimjimmy--Your R3 block was pretty good from a cursory sonic check--I checked in the usual known thin spots and they were much thicker than production stuff. I did not document it properly-I should have. Sorry. J.Rob
 
Yup. I do an inch spacing up the bore, then a scan along the entire set of points. It is common to find a thinner spot somewhere in between the previous test spots.
 
FWIW... I was perusing a '65 FSM and spotted a limit to overbore. They limited it to .040". That was the same across the board for all engines, from 273's up to 426's.
 
First 4 piston manufacturers have said the largest they go for an off-the-shelf piston is 4.07 for a small block. Anything larger is a custom.
 
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