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Old 03-31-17, 04:59PM   #1
keith
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Default Flex-plate, flywheel info

Anyone aware of any balancing issues with flywheel/flexplate? I thought they were neutral (symmetrical). Current build will be auto(flex-plate) and will send it to balance anyway but I'd like to know if theres any external balanced factory setups.
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Old 03-31-17, 05:38PM   #2
tjs44
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They are not neutral from the factory.Aftermarkets can be had either way,some with a removable weight.Tom
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Old 04-01-17, 09:04PM   #3
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So factory motors are externally balanced to a degree then. Do the various different motor sizes having slightly different rotating member weights have differently weighted flywheels? Only thing I ever heard about this was that the 400 had a different flywheel for some reason ... heard that from someone I thought might have been confusing 400 Chevy with Pontiac. Now Im the confused one

PS Going downstairs now to look at a 400 flywheel and the SFI flexplate I bought for the Kool-Aid Keith 444 to look for extra drill holes ...

Factory flywheel has numbers 52561-3 (I think they are barely visible)

- it has one fairly deep drill hole on the backside that looks like might be
for balance
- 6 holes for mount holes and 2 smaller I think to align only in 1 position?
Nope I dont know what smaller 2 are for the 6 only line up in one
position

Aftermarket SFI flywheel marked FWFP455

- doesnt appear to have any balance mods
- does have 2 small holes like flywheel in same relative position but
further out (closer to ring gear)
- kind of misleading PN .. it doesnt fit a large journal crank bolt pattern

I freaked when I put both on the end of a large journal crank I had handy and neither 6 mount holes lined up in any position .. then light bulb went off and I tried on small journal crank and they both lined up 1 position only. Guess I learned small journal and large journal have different bolt patterns and dont interchange .. probably different enough balance to make unacceptable running balance condition so they did that. Possibly the dash number on PN identifies motor size flywheel is for as well within small journal applications? Havent found reference yet. My 444 will use a Scat forged small journal crank with 4" stroke so either my flywheel or flexplate should bolt up, one will not have same balance as other most likely. Paul at Carter cryo will balance my ra with flexplate. My factory gold 71 Formula 444 with factory quarter-stick fresh black interior is getting closer
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Old 04-01-17, 09:09PM   #4
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all pontiac flywheels have the same bolt pattern.They have diff crank reg.Some after market wheels come with the large reg and a ring to use it on a small reg crank.They are all off balanced the same if a 326 or a 455.Tom
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Old 04-01-17, 10:00PM   #5
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Most of the Pontiac stuff is internally balanced, so they'll except any flex plate. But you still have to send your flex plate. But if it gets damages a new can be balanced to match your old one, no need to have the whole motor rebalanced. Same goes for Hamonic balancer. I guess that's what your calling neutral balanced. Just make sure you get your balance card, so later any shop that does balancing can do it.
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Old 04-01-17, 11:56PM   #6
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Paul has my balancer alum Romac(from Jim B). I was just thinking neutral balance means it is symmetrical exactly weight wise so it doesnt affect balance. I am sending all my ra (including flex-plate) + cam + Ti valves hopefully next Fri to Paul. He has my Romac timing set and 2cnd gen Rhoads lifters so everything moving in engine will be frostyied. Valve springs and pushrods later. Took my block to new shop yesterday, they are cleaning and remeasuring since its been so long since my crankshaft rip-off. They will check and measure my ra elements too and ship to Paul from there so no surprises ... I want to hear this thing run and sing finally ... Got to get to work on my heads and DQ setup here.

Went and tried again the flexplate on the 9782769 crank and the 6 holes dont line up in any position. They do on the 9773524 in one position. The register I believe, is the circular raised portion the flexplate center hole fits tightly down over on both cranks .. so it is not .250 different. I cant find any evidence of welding and redrilling the crank holes on the 9782769, it is the bent ebay 428 crank I originally wanted to straighten and reuse in a 400. Guess I will chock up to twilight zone. I have a nice stock 455 I'd like to use as I was thinking of throwing together a street beater 4spd car quickly(80 hardtop TA). I know flywheel is from 400. Town is after me finally and I have to get all my stuff registered so I can keep at my house.
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