Posted by Vaughn [172.68.133.159] on Monday, December 13, 2021 at 12:14:19 :
After some discussion below, I looked into what might be the biggest piston you could bore a 230 engine cylinder out to, and this is what I found using a STD piston from 251 CID:
230 – Piston Dia. – 3.250, Piston Lgh. – 3.66, Pin Dia. - .8593, Comp Hgt. 1.978
251 – Piston Dia. – 3.437, Piston Lgh. – 3.733, Pin Dia. - .8593, Comp Hgt. 1.978
Diff in Piston Length = .073 (251 slightly longer)
Diff in Piston Dia. = .187
Cylinder Dia. Increase of = 1/8 or 1/16 all around bigger cylinder
Cubic Inches = 257.46 CID or 4.2 liter
I don't know the exact thickness of the 230 cylinder wall, but the article at the link seems to indicate it is possible. Stock head gasket might work, or a gasket may have to be made to fit the larger bore. Using larger head intake/exhaust valve and porting to match between block and I/E manifold, you could probably achieve significant HP and torque boost from a single carb. According to the article, .100 wall thickness is minimum to prevent wall distortion. There could be rod/crank impact, it might be an issue over time. Other Dodge forum have mention boring the flathead out .090 with no heating issues, so this could be a fun project if someone had a spare engine and wanted to pursue it. The gain could be pretty satisfying.
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