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drive plate weight

WOTFTW said:
new idea... the motor is already assembled so i think im just going to pick up a neutral flex plate that hasnt been balanced.
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This is not a good idea, you will definitely have an imbalance problem. L67 engines require the external weight for balance. As previously mentioned, the flexplate will only bolt on one way which will locate the weight in the proper position. what has not been mentioned is that the flexplate to crankshaft bolts are tty bolts and should not be reused. I am sure a dozen people will post that they reused them, but it is not the right way to do it. If you reinstall your original flexplate with new bolts using the proper tightening procedure, you will be fine. My 2cents.
 


bobsgtp2nv said:
This is not a good idea, you will definitely have an imbalance problem. L67 engines require the external weight for balance. As previously mentioned, the flexplate will only bolt on one way which will locate the weight in the proper position. what has not been mentioned is that the flexplate to crankshaft bolts are tty bolts and should not be reused. I am sure a dozen people will post that they reused them, but it is not the right way to do it. If you reinstall your original flexplate with new bolts using the proper tightening procedure, you will be fine. My 2cents.
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Yea good advice bobsgtp2nv, I think I confused everyone including myself.

If the motor has the original rods and pistons then you should use the stock flexplate. The motor has already been externally balanced by GM. Machine shops routinely mark the rods/pistons 1-6 so the assembler won't have any balance issues.

I got new TTY bolts from ZZP on the cheap and the last motor I built is just a DD. Better to be safe than sorry.
 
can flex plates be weighted differently or do they all have the same sized counter-weight on them? back to the wheel reference... i know wheels can have different sized weights to balance them accordingly. because this is a completely different motor. i bought a reman'ed long block from marshall engines through rock auto that did not come with a flex plate and this flex plate was off my old motor that had seized. so could i use the old flex plate and put it on the other motor?
 
I know that the flexplates are different from the L67 and the L36 to account for the difference in rod weight.

Popular beleif: Any flexplate made for a L67 should work on your motor if it has the L67 rods.

My opinion: The flexplate should be balanced to the specific motor if your going to spin it to 6500 or higher.
 
After this last post I decided to google this s**t. It's driving me crazy.

This guy is asking about using the right flywheel when going from a 400 to a 454. The conversation explains exactly what we're talking about. Professional opinion says that even a much lower reving 454 can be spun to 6500 with a stock non-specific flexplate or flywheel. So maybe the L67 may be alright with the stock flexplate to a much higher rpm, like 7000 or so.

Externally balanced and flywheel/flexplate - ChevyTalk --The Social Network for Chevy Fans
 


okay heres a better question... has anyone seen flex plates from l67s and seen they were weighted differently?
 
okay thanks rico. that cleared it up so i CAN use the same fly wheel. now i need to figure out how it sits on the crank. is there anyway i can do this myself without taking it to a shop? because everything is cranked down and ready to throw on the trans. i would hate to undo the oil pan etc.
 
Is the engine on an engine stand?

I hang my engines from the hoist to put the flexplate on. Just make sure you rotate the plate until all of the bolts line up and all bolts are finger tight. Torque them down and you're good to go.
 
im going to take a look at it but i believe i can flip it 180 degrees because the bolt pattern is symmetrical.
 


See it now? This is the L36 I just replaced in my daily driver.

L36_Flexplate.jpg
2012-04-15_02-43-02_19.jpg
 


i shall indeed. thanks for the input. i learned a lot about externally/internally balancing a motor through this thread
 
Matt...it's not always that easy. Say he's NA. Well H/C/G body cars had 258mm TC patterns in NA due to the larger car. Meanwhile W's and some smaller ones got 245mm for NA.
 
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