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Internal or External balanced crank?

 
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Hanz
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2003 Dodge Ram

PostPosted: Tue Sep 27, 2005 4:47 pm    Post subject: Internal or External balanced crank? Reply with quote

I have thought about this for a week now and hate to ask it, because it is a question that I should know, but I have been in a fog lately...

I have a used 383 Chevy crank. How can I tell if it is internal or external balanced? I don't know the history of it. No numbers or ID on it.

And please save the response of 'put it on a balancer and find out' - not as easy as it sounds...

Hanz

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87calais
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PostPosted: Wed Sep 28, 2005 3:19 am    Post subject: Reply with quote

Hmmm.... without to much knowledge on cranks.... I'm going to assume it's for a two piece main seal block, cuz I'm pretty sure all the one piece are external....
Do you have the flexplate or harmonic balncer that went with it? that'd makeit real easy then.....
I saw on the back of an external balance crank had a pin sticking out of it to locate the flywheel in one position only, but I know my ls1 doesn't have that and is all internally balanced.... if it doesn't have that pin, I say it's internal... if it does.... then that one is up for grabs unless you happen to have another internal balanced gen 1 crank to compare....... But I think that's the best thought I can muster at 3 am
Peace out, and best of luck
Tim

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1979 Chevrolet Camaro

PostPosted: Wed Sep 28, 2005 9:12 am    Post subject: Reply with quote

I'm assuming this is an aftermarket crank since it's for a 383. Otherwise you'd be able to tell it's a 400 crank ground down which is external balance. This might explain the lack of casting numbers too. I checked eagle and scat and their cranks are internal balance, not sure about crower, cola, etc.

Sucks you don't have the flexplate or harmonic balancer for it.
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jonny_b
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Joined: 28 May 2003
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1979 Chevrolet Camaro

PostPosted: Wed Sep 28, 2005 10:38 am    Post subject: Reply with quote

Someone will have to stop me if i'm worng here but:

1. If it is an internally balanced crank, that would mean the crank shaft was balanced with only the rods and pisont assemblies, and there will be mods to the counter weights to achieve this balance.

2. If it is an externally balanced crank, that would mean the crankshaft was balanced with the addition of the harmonic balancer and flywheel/flex plate and the weight would be added to or taken away from these items.

So basically, if all you have is the crankshaft than what differance does it make if it was previeously internally or externally balanced, it will need to be balanced to your engine anyway, and you can have it balanced either way you want to.

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clay
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1972 Chevrolet Nova

PostPosted: Wed Sep 28, 2005 7:37 pm    Post subject: Reply with quote

I think it would greatly depend on the weight of the piston/rod combo. I have a Scat 383 crank that I bought the external balancer and flexplate for and my machinist said it might have balanced internally just as easy. Clay
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