I'm trying to get all my ducks in a line for a new xlfow. I've got a 1600 block and some new 1300 pistons that I want to use.
I've got 2 sets though, and they're slightly different. I've measured them and they both looks to be 81.9mm.
The ones on the left have 1.00 stamped on top, and the right has 040. I thought that must have been the size over std, but then wouldn't they be different dia?
 
So basically my question is, are they as good as being the same, or is there a better one to be using?
 




 
I've also got these rings. I'm guessing the 040 at the end of the part number means 0.040" bigger? So in theory they should fit the pistons marked 040 as well?

.040" is 1.016mm.
 
1.00 is .039".
 
The pistons on the right need to go to scrap metal.
 
The pistons on the left are much better in skirt design.
 
Both are rubbish for making power due to crown design, ring width and diameter.

Thanks for the info Paul. Explains why they were being sold nice and cheap I guess.
What does a decent xflow piston cost?