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By Kahuna - 7 Years Ago
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Re the thread by Mr. Quinn
What is the max overbore for a 312 block? And also a 292?
If one has a good 312 block, what is the max cubic inch possible?
Thanks
Jim
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By charliemccraney - 7 Years Ago
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Maximum overbore will vary from one block to another. If you're going to extremes, have the cylinder walls sonic checked so you know.
There have been a couple Y's in the area of 400ci but they require custom parts and expertise, so maximum displacement has maximum cost, too.
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By miker - 7 Years Ago
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Good question. I’ve always sonic checked the block, and I’ve done 2 blower motors where I didn’t use the “maximum standard overbore” due to wal thickness. In one case we shifted the bore centerline slightly to move away from the thin spot. Better smaller than wetter.
. Edit: Beat me Charlie. On my 340cid stoker 312, we had to clearance the rods from the cam.
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By PF Arcand - 7 Years Ago
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.A note from Ford, they only made pistons for 312 s up to 40 thou over. (aprox. 319") However, many have bored them 60 over & usually it's o.k., but a sonic check is a good idea. That results in 322 cu. in. Beyond that is sketchy & if you have a problem with say a broken ring, then what?. And as Charley points out, with a custom order crank & much smaller rod journals & so on, it's possible to go quite big, but it requires special expertice & big $$$$ !!
P.S.- Jim; If you want to get info on a stroker kit, John Mummert Machine has kits that will get you into the 330+" areas. Link from this site to his site, it's very informative..
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By Kahuna - 7 Years Ago
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Thanks so much
Jim
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By famdoc3 - 7 Years Ago
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I'm .80 over with Egge cast pistons and trouble free. MIKE
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By Kev - 7 Years Ago
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As mentioned from a bunch of guys: sonic check the block. That’s about $90. Probably money well spent. Then go from there. I just picked up another 292 block with stock bore for $100. So, determine what is logical/feasible. Unless boring to the max and stoking the motor out is your thing. Of course, that gets expensive.
Good luck
Kev
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By PF Arcand - 7 Years Ago
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Mike: Was your block sonic checked before the 80 thou overbore? And were you starting with a 292 or 312?
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