Rotating assy balance

Tays340 said
After watching several videos on the process, seeing that each end of the rod is weighed and then belt sanded if needed to get within tolerance, same with wrist pins and pistons if needed so each assy is within x grams of each other, then do the math build the bob weight etc which is why I took it to a professional(?) to begin with. But, just looking at the caps for #5 & #6 there is no way those two rod ends weighed within tolerance, and they're on the same journal.
I've got another bottom end. I'm feeling I need to start over. I've got too much invested in my Mopar to have the bottom end malfunction and I ain't feeling good about this.

I had to go back and look at your picture. I’m ASSuming it’s 1-8 from left to right. If that’s correct then you are saying the number 5 cap is heavier than the number 6 cap by looks? It very well may be.

Again, I’m saying you don’t weigh the caps separately from the rod. They are weighed together by the end.

Just an FYI so you know. Chrysler had the most piss poor balance tolerance in the business. I’ve seen rods that were 30 grams (could have been a bit more than that) from the heaviest to the lightest big end. All on the same crank. They used what I’ve been told was “mass balance” and I’ve yet to get a definitive answer to what that even is. I know they didn’t shake but that doesn’t mean they were balanced to a reasonable amount.

The only way you will ever know if the shop didn’t balance the crank correctly is to knock the pistons off the rods (a giant pain in the *** if you don’t have the right tool and fixtures and if you don’t the possibility of breaking a piston is much higher than actually getting one of without breaking it) and measure each end on a scale. And then you have to weigh all the pieces, make up the Bob weights and spin the crank to see where it’s at. You’d literally be paying for a second balance job.

Looking at them with your eye or weighing them on a scale means nothing. Is there any thing other than visually looking at the stuff that makes you think they didn’t get it right? I’m asking because I still don’t know why anyone would tell you swap caps from one rod to another one. That makes no sense.

If you need to verify something, take the rods and pistons to a different shop and have them remove the piston and end weigh each rod and let you see how close they are. Even if there is a 5 gram spread between the rods it won’t make a pinch of **** difference.