Replacing Rod Nuts...does a balanced engine need to be rebalanced?

...Compare the Weights on a Digital GRAM Scale.

MJ

Just throwing this out for consideration, but if you’re changing all the nuts, you would change each part of the rotating assembly by the same amount.

You are also changing the weight in a balanced fashion… every 90* of rotation.

Of course, the total rotating assembly mismatch is balanced by adding “Mallory Metal” or removing material at the crank counterweights, but I would think you are changing material in a very balanced manner, AND you are changing weight by a very small amount (relatively) close to the crank centerline - where it would have less effect than if it was at the piston end of the rod.

Question:  Why are you changing the nuts?  It’s been a long time since I researched this…

Rocky

I agree with Rocky. As long as everything is equal, you're OK. That being said,  I wouldn't mess with it. You'll be stretching the rod bolts one more time. By installing new nuts, you may not be making the assembly less likely to fail.

By the way, why does ARP package their nuts in quantities of 10?  It should be in quantities of 8. I always have 4 left over !!!   

Rocky, great points...thats why I asked, there are smarter minds here. I'm not familiar with the processing of balancing but wanted to ask. With the nuts being close to the centerline any difference would be minimized. Thanks for the insight...it clicks when someone explains it the way you did.

I'm going to find a gram scale and check the weight.

There are a few posts where George discussed rod bolt "nut failure". Here's two:

Yep, I remember that now…. Thanks for posting…

David Nunn, I did not think replacing the nuts could weaken the rod bolts...geez!!!

And I agree when you ask: why don't they sell them in packs of 8, maybe because they know you'll drop one or two and they'll be lost forever! And ya just never know when you might need one more rod nut!

Ford used a 26.2 in-oz balance factor while builders often used 26 in-oz. so the rod nuts used likely mean nothing unless you're racing for money. Plus, there were two different factory rod bolts (hopefully with appropriate nuts). The angle-head standard bolts and the stronger 'football-head' bolts for the higher revving Boss-351.

Many old-time builders discarded the angle-head bolts as a matter of preference, so after 50 years who knows what's in there now?  But unless you like exploring the above-6000 rpm range on your tach, it makes little difference to most of us.