Bad Girl

I recently had my rotating assembly balanced in a BBC. I have decided since then to change the rods. do I need to rebalace the entire assembly again for crank counterweight? I changed rods from 6.625 to 6.535 lenght.
Thanks for responses.
Ken

vette131

yes

GPM

I hope you changed pistons, they may sit a little low in the cylinder. I would re-balance.

robyw1

What he said ^^^

formula31

Unless by some chance you know the weight of the existing rods and by some miracle the weight of the new rods is the same. And of course that would have to include the new pistons too.

Bad Girl

Thanks for the input. I am using the same pistons to get the desired compression. the longer rods were a mistake in what was shipped. should have measured before I started.

JCPERF

Make sure the crank is cam cut to clear the bottom of the pistons.

Crazyhorse

The shop that did the initial balance work should still have the work sheet with all the component weights. the machinist will just need to weigh and balance the rods, and then balance the crank with the corrected ring/piston/pin/rod/bearing weight.
The short answer is as everyone else has said, yes. Don't cheat now.

Tinkerer

I would think that if you can get the new rods to weigh the same as the old rods you should be OK.
I believe that the big end weight has to be the same also.

Crazyhorse

Tinkerer, are you thinking that you can add weight to a rod to make the 6.535 rod weigh the same as the 6.625 rod did?