First post, want to thank the forum as I have pulled so much info from old threads. But could not find this info. I have a LM7 that I’m putting 4.8 flat top pistons in. The 5.3 pistons + rings has a mass of 445 grams, The 4.8 flat top pistons +rings weigh 440 gram. Is there any benefits to have rotating assembly balanced, or just move on as I assume everyone else who asked this question on this forum has done

 

5 grams isn't that much. Many have done this without balancing, but it would be better if you did.

 

The pistons are the smallest portion of the balance. I think you will be just fine without balancing the crank

 

You'd be surprised how much it actually takes to feel a vibration from a balance issue. You're looking at 30+grams to really notice a balance issue.

 

So I've been wasting my $$ to balance within .5 gram and run 8000rpm?

 

OP isn't running 8k RPM....

 

Maybe I am misunderstanding this, but are you changing one or two pistons or the set. If its the set, then there is no issue. If it is one or two, five grams while not ideal should not throw it out of balance.

 

Not at all.