balancing rotating assembly

what would you take as a max dif in bobweight when changing rods to get the crank balanced again?
running 526 ci BA hemi at 9500 rpm
thanks danny

 

If you are going to a lighter total bob weight it would make the crank "over balanced". That may not be a bad thing if the crank was balanced at 50% from the start. If you are going the other way I would have it balanced again for that kind of RPM's.

 

what % would you accept before balancing the crank again?
we have other rods and the dif is 2.5 % ?

 

2.5% of the total bobweight? Then I would rebalance.

 

rods

We were in the same boat with Brooks shutting down. The weight on the big end is more critical if it changed a lot. I know a lot of guys are switching and ending up with 15g differences and running it. I think we are 10g lighter but haven't run it yet.

 

Overkill... what rods did you go with? dave

 

15 grams would be less than .5% on most blown engines. That will not cause any trouble. The crank is balanced from the center out. If the crank is heavy by 10 grams on both sides from center, that won't cause any damage. If it is 5 grams heavy on one side and 15 grams heavy on the other, that will cause it to rise and fall [shake] on different planes. 2.5% would be over 50 grams! I would rebalance it.

 

Balancing

Ok I have heard of 50% 51% & 52%
What should a hemi be Balanced at ?

 

rods

GRP per Bill Doucet...real happy so far.

Mike

 

52% for engines turning 7000+ rpm's is what I was told by the tech at Sunnen when I purchased my balancer.

 

we are going over from the mgp to the fowler and they are heavier on the big end and lighter on the small end
but if you change rods to get the compression up or down you can't balance the crank for all the dif rods you want to use can you?
engine is a blown 526 ci BA
thanks for the info guy's