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Internal vs external crank balance

2K views 4 replies 4 participants last post by  DZAUTO 
#1 ·
Is the GM p/n 3967416 crank an external balance or internal balance crankshaft? Is it possible to use an external balance crank and internally balance the assembly?
 
#2 ·
JIm,
What stroke is that crank?
All 396/427 stuff is internal balance.

Yes you can internal balance most external cranks but it can get very expensive quick depending on the weight of parts.
You use Tungsten slugs at about $80-$100 per piece installed.
 
#3 ·
It is a normal 4" stroke, 1970-1990 454 crank. I am looking at a shortblock in my area that is for sale. It has that crank in it, but I want to go internal balanced, not external. So I need to figure out if it would be feasible to do or sell it and buy a Callies or Scat. I assume that since it is a stock GM 454 crank, then it is an external balance type?? Heck, I don't even know if it is forged or cast??? Haven't seen it yet.
 
#5 ·
I agree with Jim.
All that is required for balancing a 454 crank (as well as a SB400) is an UNbalanced harmonic balancer and an UNbalanced flywheel (or flexplate). Those 2 are very common items, and when supplied with all the other engines parts for balancing, a good machine shop will give you an excellent balance at the regular price for balancing. As mentioned, to INternally balance an engine which is NORMALLY externally balanced, can cost 2-4 times what a regular balance costs.
Unless this is a serious, hardcore race engine, stay with the EXternal balancing.
 
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