Looking for new pistons for my 496. Found some that are 10 grams heavier per piston, so 80 grams added to the bob weight. Would you run it as is, or rebalance? Thanks Matt

I would see if you could take 10 grams out of the new pistons.

That's not how bob weight works.
You would only be 10 grams off on your bob weight.

Run it. Never hurt a thing.

Lighter is better when it comes to motor parts and driveline parts Remember the rod and piston stop three times and reverse directions twice for each cranshaft revolution Lighter weight parts stop easier and accelerates easier than heavy parts do

Sorry, missed the math.
How does 10 grams X 8 cylinders X 50% (for reciprocating weight) = 10 grams?

au

Well I will never be as smart as you but you still don't get balancing an engine.
Each throw is balanced.

And it's one piston weight one pin weight one ring pack weight one set of lock weights.

This is reciprocating weight.

Rotational Is 2 of everything on that end.

So it's 10 grams per throw never going to hurt a thing.

You think oil on all parts in that mess is with in a gram.

10 grams is within factory tolerances, might be a little out of spec for a race engine. Shouldn't hurt anything in a normal bracket engine, maybe a tiny bit of vibration at lower rpm but you might never even notice it.

I agree. Then it would be balanced as well as before changing pistons.

Being rude is the fun part, isn't it?

As said 10 grams diff you're in excellent shape. However you could easily deburr a few grams off of the new piston (not sure how much but maybe even the whole 10!) and BB pins are way bigger than what is needed & even for a racing app you can safely mill up to 1/4" off of each end of the pin to lighten it to match parts for the recip part of the formula if you have a lathe (dont mind me its just my OCD/too much coffee!)

I wouldnt worry too much about it but you could weight a set of KING SI rod bearings. They are usually a few grams lighter than trimetal bearings. 2.5 grams for each rod set would would be parity with the heavier pistons.

They are probably more than 2.5 grams lighter but I would rather be a lighter than heavier.