Any machinist?

What are acceptable tolerances for the weight of rods and pistons?
If the whole set it within 2-3 grms of each other, is that fine, or is there a set weight?

.5g for performance stuff.

Thanks.

It depends on what you are doing. We usually keep stuff within a gram of each other. What you are talking about though would run forever on any street engine and you still probably wouldn't even know but if you are paying for a balance job it should be better than that usually in my opinion.