Piston weight

I'm installing new 8.5:1, pistons in my 0320 to convert to 160HP. Three of my pistons are within 2 grams of each other and one is 18 grams heavier than the lightest piston. 18 grams seems excessive to me. Is this something I should be concerned about? If so, where is the best place to remove some material?

Thanks!

Yes, 18 grams is excessive. I think I would contact whomever you purchased them from. I'm assuming you bought them as a set.

More than excessive, it seems to be double the factory tolerance.

This is from the Performance Engines web site -

Also, Performance Engine's Pistons are balanced to within 1 gram of one another in opposing bays. OEM pistons tolerance is 14 grams.

A local engine rebuilder should be able to complete the balancing for you.