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Engine Balance 

 

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 Post subject: Engine Balance
Posted: Mon Jun 04, 2007 10:03 am 
Oompa Loompa
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The 342 Ford Racing crate motor I've just bought has a 28oz balance factor. The AU XR8 flexplate and harmonic balancer that I need to swap onto the motor has, I suspect, a 50oz balance factor so I assume that if that is the case then I am going to have to rebalance the 342 (do I?). Can I just drop the bottom off it (I have to swap the sump anyway) and pull the crank and rebalance the crank, flexplate and damper without having to strip the rest of the engine to pull pistons and rods?
In case you're wondering, I bought the engine before I found out the potential balance problem after reading another post on here about someone enquiring about light flywheels and the balance factor was mentioned.
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Posted: Mon Jun 04, 2007 10:06 am 
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I would have thought it easier and cheaper to get a new balancer and the flexplate balanced to 28oz then to strip the motor down and get the rotating assembly rebalanced.

 

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Posted: Mon Jun 04, 2007 9:46 pm 
Getting Side Ways
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i got a short built and decided on another different trans , so now i gottra send all back and get balanced again just to be sure , bumma hey
on the other side ive run clevo with a leg out and no balancer before , i must say there was a slight bit of vibration , ok a bit more than slight
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Posted: Mon Jun 04, 2007 10:16 pm 
Getting Side Ways
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if you know it need 28oz get the flexplate balance changed to suit or buy a new flexplate with the corect balance
no need at all to go the extra effort and money to rebalance an engine just to use a flexplate you have.

 

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Posted: Mon Jun 04, 2007 10:18 pm 
Getting Side Ways
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Just buy early windsor flex plate mate, all good.
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Posted: Tue Jun 05, 2007 12:34 am 
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You will need to use a 28oz flexplate and 28oz balancer. The flexplate will be easy because you can just buy one to suit an earlier 28oz engine or have your AU one match balanced to an earlier 28oz flexplate.
Your balancer however, is more difficult because it has an integral pulley and was unique to Explorer/AU engines. It will need substantial machine work to bring it to 28oz spec.
This pic, although showing manual flywheels shows the difference in balance weight sizes between 28oz(bottom) and 50oz(top) types. You'll need a similar reduction with your flexplate.
Image
These pics below show the AU5.0 50oz vs 28oz 351w with our custom encoder wheel fitted. The pics aren't great but you can make out the size of the counterweight on the AU one...it's considerably larger so will need substantial machining to bring it down to 28oz. It's still your best option as earlier balancers will require a custom crank pulley(and our encoder wheel) to provide the correct pulley offset and diameter for AU front dress.
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Posted: Tue Jun 05, 2007 12:36 am 
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what pulley is that on the right

 

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Posted: Tue Jun 05, 2007 12:41 am 
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AU left, 351 right.
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Posted: Thu Jun 07, 2007 7:06 am 
Oompa Loompa
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Awesome reply XR9UTE, you are a wealth of information and I really appreciate you taking the time to explain it all and providr pictures showing the differences. I have been able to source an early style 28oz flexplate (specified for a C4 but I assume the 97LE torque convertor will bolt up to it OK. And I may have a balance shop that can rebalance the AU/Explorer damper.
Once again, thanks for your help.
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Posted: Thu Jun 07, 2007 6:57 pm 
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No wuckers Junior, My pleasure.

I believe your C4 flexplate will work but it needs to be from a large bell C4...therefore it should have a 164T ring gear not a 157T one.

Pete.
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