Is it possible to swing a 4.25" crank in standard 9.8" block? I was thinking of using a dart big m block w/ 4.600 bores and a 4.25" stroke, but don't want to go to a long block. Also, does anyone know what GM casting would be comparable to the big m in bore diameter? Is there another block I should be considering?

I have seen a 4.375" stroke crank in a 9.8 block with a 4.560 bore - Mark IV bowtie.

Was supposed to be a stealthy street motor - LOL - pretty tough to hide the 2 3/8" headers!!

MAT

Speed-O-Motive sells rotating kits for the 4.375" stroked rotating assemblies in 4.50", 4.56" and 4.60" bores for standard deck height blocks so I figure it's OK.

I would use a minimum of a 6.44" long rod tho and go with a piston to fit...

I have looked into making a 588" motor, (4.625" b x 4.375" s), just for the heck of it if my 496 doesn't give enough third gear grunt..

pdq67