Planning a new engine and one thing leads to another The new rods/ pistons I want to use will be 435 grams (per rod/piston) lighter than the old ones. This adds up to 7.658 lbs.

Can that much weight be taken off of a standard weight crank? Or do I have to buy a lighter one.

This is SB, and the std wt. crank is 58 lbs. The lighter one is 52 lbs. Thanks

Ask the crank manufacturer what bobweight the crank counterweights will balance. Calculate what bobweight your parts will need. Then ask the balance shop about taking weight difference off.

I had the counterweights on my crank turned down on a lathe to get close to the bobwieght of my parts. Then the fine balance was done with small holes drilled into the counterweights. Mine is a big block, so it is different, but the crank counter weights were turned down from a bobweight of 2500 grams to 2185; and that was a lot.

Thanks, I went looking @online catalogs for bobweights listed a few minutes last night. I know I seen #'s listed somewhere.

IIRC that's not far from the bob weight differences I had going into the new motor build.

So yes, I think it can be done using your existing crank.

Looks like good news although I'm kinda puzzled by it. The Std wt crank will work. Found the big/small end weights (440g/180g) and they figured bobweight to be around 1790 grams. The balancing bobweight for their cranks are;

Std.wt~1800grams
Lt. wt.~1650-1700
Super lite~1600
This is for 340 main/3.58 stroke Scat crank.

I'm curious as to what the weight of a factory 340 (forged) crank is now. Maybe a trip to the garage w/ the bathroom scale is in order.