Hey guys,
Got my NOS 390 crank back from the shop for cleaning up some surface rust from all these years. The mains are STD, but the rods are 0.001" under and that undersize is no longer available.

So, since the crank has to be turned 0.010" under, I am considering going in a couple of slightly different directions with rods/pistons ... Can I get some feedback from you guys that have stroked cranks before. Just a reminder, this is on a 304 Stroker motor.

OPTION 1 - Leave the 390 crank at 3.574" and run a 5.85" SBC 2.100" journal Rod with a Keithblack 1.561" compression height SBC 305 flattop piston (5cc reliefs), which makes a ZERO deck at 9.198". Yields 10:1 compression with 63cc heads. This would be a 323.6 CID stroker (3.796" bore 304 block). Note: Rods & pistons would be matched, so no bushing work would be needed.

OPTION 2 - Leave the 390 crank at 3.574" and run a 6.125" SBC 2.100" journal rod with a Keithblack 1.261" compression height SBC 305 half-dome piston (-2.8cc top), which puts the piston at 0.025" below deck. Yields 9.8:1 compression with 63cc heads. Same 323.6 CID stroker and rods/pistons are matched ... no rod work needed.

OPTION 3 - Offset grind the 390 crank for a 2.00" SBC rod, stroke to 3.75" and run a 5.7" SBC 2.000" journal rod with the Arias forged 232/258 domed pistons (1.595" c/d) I picked up. This combo puts the piston 0.028" below deck and yields 10.1:1 compression with 63cc heads. NOTE: The Arias pistons have 0.931" AMC pins, so the SBC rod bushing would need to be slightly reamed from SBC size of 0.927". This would be a 342 CID stroker (3.81" bore x 3.75" stroke). NOTE: To get my crank offset ground would be $200 (as opposed to the $100 for a regular regrind on option 1 or 2). FYI, I would run H-beam rods for stroker clearance.

While I am leaning towards option 1 or 2, option 3 at least looks promising. Since I have already had my NOS 390 crank cross-drilled (years back) ... would there be any issues with offset grinding a cross-drilled crank? OR for that matter, grinding down from 2.249" AMC journal to a 2.100" SBC journal?

Thanks all for the feedback ... and ... good night!


Sincerely,
Greg Taylor :) <><