273 302 318 340 build

OK very good info. Seems like a lot for each .010"..... I was expecting maybe half of that???? You may find it is not all that much when you get them. But lemme plug in an extra 30 grams ..... and yes, the bobweight goes up from 2202 grams to 2232 grams, or about 1.4%. This is all assuming you have the later 318 bottom end with the heavier rods (same rod weight as the 360's).

For revving, yeah, I personally would re-balance. While typing this up, bingo... I remember this conversation with the machine shop over 40 years ago when overboring for my first performance build: "You really need to rebalance this engine with the new oversized pistons" Which I had them do, despite being a poor sailor making just over $450 per month....LOL!

BUT, IMHO this needs to be done by lightening the pistons and pins and small ends of the rods; doing it just at the crank will require ADDING weight on the crank counterweights.

Too bad you can't find a set of KB pins at 132 grams.....Diamond after-market ones are probably way too pricey. Or drill out the stock pins to get rid of most of the added piston weight and take the last bits out of the pistons.

BTW, all of the reciprocating weight part of the bobweight calculations ends up there in the pistons, rings, pins, pin locks (if any), and rod small end, so any of them can be lightened and have the same effect on balance.

One other (probably insane) idea: Confirm what the Sealed Power 814's come in at. They are Magnum 5.2 pistons. They have the same general overall weight listed as 761 grams for piston + pin, but a much lighter piston alone at 534 grams per the FM site, so the pins must be monstrously thick walled so they can be drilled out at will. These are hypereutectics (not regular eutetic cast) but oughta work fine. The one thing that I don't know is if the rod width area under the piston is as wide as in the 526AP's; the Magnum rod's small end is a bit narrower. Oops.. the 814's look pricier.....well, just throwing that out there.