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Old 02-25-2005, 09:37 PM
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harmonic balancer/damper choice

i just purchased a 383 motor that was rebuilt 5 yrs ago and all paper work is missing, it has never been run.....i also prchased a 6-71setup that has been run 3 times.....block assembly is missing a front damper,,,,,What / Which do i need to purchase? one for internal or external?....one advisee over the phone said to pull the pan and measure the rods for a 5.7 or 6" , but couldnt tell me what choice goes with what!!!
after choosing the right type, is bigger diameter better?

thanks to all in advance

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Old 02-26-2005, 08:13 AM
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I have never messed with stroker motors but what I have heard is the 383 is a 350 block bored .030 over giving 355ci with a 400 crank giving 383ci. The 400 assembly is usually externally balanced. With that being the case you would need a damper for an externally balanced 400. But the assembly can be internally balanced. With out knowing which way the motor was built its hard to give a correct answer. If I was doing it I would get the 400 balancer and try it. If its wrong it should vibrate a little. If thats the case you will have to have the motor rebalanced.
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Old 02-26-2005, 08:30 PM
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Quote:
Originally Posted by douhavit
i just purchased a 383 motor that was rebuilt 5 yrs ago and all paper work is missing, it has never been run.....i also prchased a 6-71setup that has been run 3 times.....block assembly is missing a front damper,,,,,What / Which do i need to purchase? one for internal or external?....one advisee over the phone said to pull the pan and measure the rods for a 5.7 or 6" , but couldnt tell me what choice goes with what!!!
after choosing the right type, is bigger diameter better?

thanks to all in advance
Pull your oil pan off, bring it to the advisee you talked to over the phone. When he gets close enough crack him over the head with it.

5.7" rods and 6" rods don't affect the balance of the crank. You most likely have an externally balanced 400 crank.

Don't try it and listen for a vibration. You will probably never hear it. As far as an easy way to tell the difference, I don't know. One of the machine shop guys on this site may have an easy way.
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Old 02-26-2005, 08:54 PM
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You wont hear it but the one time I was wrong about it I could feel it. Had to replace the bearings and have it rebalanced.
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Old 02-26-2005, 08:57 PM
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Would he be able to see the Mallory in the crank if it was internally balanced?
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Old 02-26-2005, 08:58 PM
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Did you get a flexplate of flywheel with it? And yes, most likely you'll have a few slugs of mallory in the counterweights of the crank if it's internally balanced.
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Old 02-26-2005, 09:12 PM
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The only 400 crank MORTEC lists is casting #3951529, cast crank. Looks like your best option is to pull the pan and get some numbers.
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Old 02-26-2005, 11:16 PM
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most of the locals agree that it is external from their experience and original engine owner doesnt remember paying extra for the internal balancing....no flex plate was provide , so i will assume to get the 400 version for that....are there any recommendations for a "sturdy" enough brand to handle the 6-71 and how do y'all feel about the Fluidampr version
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Old 02-26-2005, 11:29 PM
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You are going to be spending a lot of cash on the forced induction. If it were me I would want to know exactly what was in the bottom end. I would want to make sure the bottom end is going to hold up to the increased stress.
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Old 02-26-2005, 11:53 PM
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Quote:
Originally Posted by douhavit
most of the locals agree that it is external from their experience and original engine owner doesnt remember paying extra for the internal balancing....no flex plate was provide , so i will assume to get the 400 version for that....are there any recommendations for a "sturdy" enough brand to handle the 6-71 and how do y'all feel about the Fluidampr version
An SFI rated flexplate will be fine. BHJ or ATI super damper. Two of the best manufacturers out there.

http://www.bhjinc.com/2dynamics/dampers/precision_dampers.htm
http://www.atiperformanceproducts.com/products/dampers/dampers.htm
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Old 02-27-2005, 09:55 AM
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There is alot of controversy about whether or not the fluid dampers are a good thing or not. I have heard they can cause the crank snout to break and that the fluid becomes ineffective at dampning after some time. I dont know if either are true, but I would just get a quality SFI approved damper and forgo the fluid.

As for the flywheel, thy dont get better than the JW "Wheel". They are expensive, but are about the best out there. But, I have one so I am kindof partial. I can guarantee you it will not break no matter what you give it. That is what I wanted.

Chris
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