Technical I have a question for someone who has experience with balancing an engine assembly.

I recently had my small block chevy rotating ***embly balanced. When I got home to look at the parts I noticed that they used the weight of .010 under rod and main bearings (I say that because both my mains and rod boxes were opened up). They are the ones that supplied the bearings and turned the crank down to .020 / .020 under. My concern is if they just offer me the correct .020 under bearings will that have a LARGE enough effect on the balance job that was done using the weight of the .010 /.010 under ones to be concerned about?

 

Bearing clearance isn’t looked at for balancing. Are you saying the mains were turned .020 as well as the rod journals? Or?

 

But they always want the bearings you're going to use on hand to weigh them when they balance the rotating ***embly

 

I’ve seen a balance job happen, may have been my eyes playing tricks, but never saw bearings on the rod journals when I watched it.

Edit: I re read I see you said to weigh them. Makes sense.

 

Then again, the weight difference is negligible, i wouldn't worry

 

They weigh everything, pistons, rings, rods, inserts and etc. some machinists also want your harmonic balancer and flywheel/flexplate. Then they put plum weights on the journals.

@supercab78 do you trust the machinist the balanced your motor? Ask him, perhaps they just sent you home with the wrong inserts. That happens from time to time.

 

Not only is the weight difference insignificant, the bearings are much closer to the the axis of rotation. It shouldn't be a problem and your engine would probably be better balanced than most rebuilds, if everything else was done correctly.

 

That could be around 3 grams difference in bearing weight. The mains are out of the equation because they are fixed. The rods being reciprocating are a factor. I would go back to the machine shop and see exactly what is what. While this is a minor amount, you need to know for sure that you got what you paid for. Be calm and polite. Good luck with your results.

 

Both main and rod blister packs were opened, so it makes sense that they weighed them. Not sure why the mains were open, maybe by accident.