318 Connecting Rods and Crankshaft

Garrett Ellison said
Thanks for reminding us! That's one of those details that I've forgotten about along the way that sneaks up to bite during building this type of stroker. One advantage is it lightens the pistons and therefore the bob weight even more having to do that. With 68 chambers and the aforementioned parts and clearances, dead on at 9.5.

Clearancing skirts removes a very small amount of weight from the piston so not much help there. BTDT.... Cast 318 pistons and stock 318 rods (heavy or light) are going to require a considerable amount of weight to be added to any stock 360 crank to internal balance if that is what is desired. An option is to go with the 360 external balance parts at the damper and TC/flexplate to get much closer.

So just be aware....

pishta said
" A 4" stroke makes it very hard to impossible to balance internally without adding weight to the crank."
An Eagle forged 4340 360 mains 4.00 crank has a bobweight of 2050g (same as their cast). Stock balanced rods and cast stroker pistons were 40g under this bobweight, that's lightening the crank, no metal added for internal balance. Not hard, and I used 'heavy' stock rods.

Pishta's roughly 100 gram drop in piston/rod bobwieght from stock is all in the much lighter stroker piston weights that he used. Stock 318 cast pistons have very thick and heavy crowns and their bobweight with stock heavy rods is going to be around 2160 grams.

The 2050 gram design bobweight number of the Eagle 4" crank number is pretty amazing; the SCAT 4" cast crank has to have under 1760 grams bobweight to internal balance without added weight. (I doubt the SCAT forged crank will be that much higher.) Not sure WHERE Eagle is putting all that extra counterweight..... I'd like to an actual pix of the Eagle crank to compare to my cast SCAT 4" crank. I've been skeptical on the Eagle target bobweight number for a 4" stroke.... but I may be all wrong on that.