On the fence about my last balance job

[Mike T]

First off I'll say after the assembly was balanced it idled very smooth and was smooth at all rpms even with HR mounts.

Now that it's time for a rebalance with a new forged crank I'm weighing a few things before it goes to another shop. Don't have the equipment to check the old crank itself so I'm just weighing small parts to get an idea of what kind of tolerances where held since there was no balance card supplied.

Pistons, rings, pins and clips weighed in @ 725.2-726.9 ( 1.7 grams difference) with no obvious material removed. Rods with inserts 727.8-729.9 (2.1-difference) with material removed from the big end only.
No fixture to see where the rod ends weigh in.


Total weight of everything assembled 1454.1-1456 .4 (2.3 grams difference)


I don't think 2 grams (the weight of two spiro-locks) is too bad in my book.........my concern is where the material was removed from on the rods. Rather than remove it from the side the shop decided to remove it from the ribs on the rod caps. I don't know why they choose this area but what's done is done.

Rather than having the next shop do additional work to the rods (more material removed) I'm considering letting it go and just do bobs on what's already there.

Any thoughts on this?? Two grams worth chasing?

 

[Mike Licht]

Nope,

 

[Phoneguy]

Depends on how hard you are going to push the car. There is rotating weight and reciprocating weight. My pistons and rods are balanced to a half of a tenth of a gram , yes .05 grams. Built at Richard Clark's , he has a rod fixture to weigh both rod ends. It was a little tedius to get them all to this spec !! I balanced it all myself. I have shifted my car at 6750 and it runs fantastic.

Bryan

 

[bison]

2g. The oil allowance could create more imbalance than that


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[Mike T]

Depends on how hard you are going to push the car. There is rotating weight and reciprocating weight. My pistons and rods are balanced to a half of a tenth of a gram , yes .05 grams. Built at Richard Clark's , he has a rod fixture to weigh both rod ends. It was a little tedius to get them all to this spec !! I balanced it all myself. I have shifted my car at 6750 and it runs fantastic.

Bryan

I can really appreciate the perfection that you have achieved....having access those tools must be nice. I'm guilty of obsessing over little items and in some cases end up doing more harm than good.

2g. The oil allowance could create more imbalance than that


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That is an excellent point. After reading a couple of bob weight cards some estimate 5 grams for oil.

I still have to question how the shop has done a reasonable job of balancing but yet made the mistake of removing material from a critical area on the rod.

Nope,

Thanks for the input Mike..... I'm sending you a PM about a different topic.