The best rod ratio you can get with the 4.75 stroke crank would be with the DeSoto rod which is 8.00". This would give you a 1.68 ratio compared with 1.64 with the 7.75" rod in the 265. The 250 has a 1.75 ratio with its 7.875" rod. You state the 'small' motors have a 2.00 rod bearing journal but my Motor manual shows 2.061 so offset grinding the crank would only give you 4.810". Note: offset grinding a crank .125 only yields a .125 gain in stroke as you only move the centerline of the journal half the offset in relation to the centerline of the crank. We always sroked Stock and Super Stock cranks .020 u/s to get a .013 stroke increase ( NHRA rules allow +.015 ). Piston speed is talked about a lot, but this is kind of 'old school' thinking. Years ago 4000 fpm was considered the limit ( kind of like the sound barrier I guess). My old boss used to turn his 352 Ford 9100 rpm across the finish line, that's 5300+ fpm. Engine survival has more to do with oiling system prep, rod big end prep, and reciprocating weight ( light is good, heavy is bad ). I've been doing a little research at the Silvolite site and it looks like a piston for a 194 Chevy six will work in the 'big' mopar flathead six. Of course the pin dia. is a little big so you would either have to modify the piston for keepers or the rod for a press fit, but you get a nice 5/64 ring groove width for a set of moly rings( this is a sore spot when building an old engine because most have WIDE rings and you can't get a good moly ring set). This works out good with a little extra to remove off the top for a 4.75 stroke with the 8.00" DeSoto rod or offset grinding the crank to 4.810 and using the 7.937 Plymouth rod.
[This message has been edited by DEL (edited 10-18-2001).]
[This message has been edited by DEL (edited 10-19-2001).]
