external engine balance
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external engine balance
OK, I received the longblock (410FE) and it came with a flexplate and aftermarket neutral balancer. When I switch to a flywheel (428/410) for manual tranmission do I need to have a rebalance or just bolt on and go? The engine has all new internals and has been balanced but with the flexplate. Any help appreciated. Thanks
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From: Stanley, VA
It's never a bad idea to balance everything as an assembly. But seeing as this is a new rebuild, as long as the original specs were used, you should be okay with bolting on the stick flywheel. Factory 410/428's used a counterweighted flywheel and a neutral balanced harmonic balancer.
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I was hoping that would be OK. The shop I purchased this from included the work sheet with all the numbers for the balance. Everything is fresh and assembled (new pistons, overbore, crank polished, rods resized, etc. etc.) Would seem a pity to have to tear it all back down to switch over to the flywheel. Thanks for responding.
Hotshot
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From: iowa
look at your flexplate carefully. I lot of lazy shops will balance by welding or drilling on the flexplate/flywheel and the dampener (this is not the proper way but it's the lazy and cheap way of doing it and a LOT and I do mean a LOT of small shops pull this stunt)
If you see where weight has been added to the flexplate then you have a lazy shop and A. never take any work to them again, and B. you will need to have it rebalanced.
If you see where weight has been added to the flexplate then you have a lazy shop and A. never take any work to them again, and B. you will need to have it rebalanced.
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Weight matching ALL pistons with pins
Weight matching rods, total weight plus each end.
Zero balance flexplate/flywheel
Zero balance balancer
Spin balance crank, balancer, flexplate with weight bobs to represent rods/pistons
Then drill the crank throws or drill and fill with mallory for a NEUTRAL balance.
Most shops would say screw that and just throw the crank, balancer and flexplate on the machine and then drill away.
Josh
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The balance card shows, piston, piston pin, piston rings, pin locks, total rod, insert, rotary, reciprocating and bob weight, all in grams. It makes no reference to crankshaft, balancer/flexplate. This was done on a Hines Microcomputer Balancer.
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Hmmm... they would have had to do something with the crankshaft if they totalled bob-weight.
Does the flexplate look drilled?
It should look similar to the flexplates listed at 428Cobrajet...
428 Cobra Jet Flexplate Identification
Does the flexplate look drilled?
It should look similar to the flexplates listed at 428Cobrajet...
428 Cobra Jet Flexplate Identification
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Flexplate looks identical with exception of the triangular cut outs. Same part number (FOR-C6SP-6375-A-Assy), looks like weight covers 21 teeth on the flexplate. I see no new weight or signs of it being drilled (other than the two drill holes on the weight).
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If they did drill on the flexplate you may have to completely disassemble the engine to have the rotating assembly balanced with a flywheel.
Josh
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Yea, I think I'm screwed. I have yet to pick up a flywheel. Can a shop check the balance (or imbalance) on the flexplate vs. flywheel to see if there is a difference in weight, etc. something like match balancing? If the weights were different than it would be obvious, need to rebalance the assembly. 
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Yea, I think I'm screwed. I have yet to pick up a flywheel. Can a shop check the balance (or imbalance) on the flexplate vs. flywheel to see if there is a difference in weight, etc. something like match balancing? If the weights were different than it would be obvious, need to rebalance the assembly.
But checking some highly recommended machine shops in your area would net you the best answers.
Josh
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From: Big Sky Country
