GM 454 gurus. I need your help please

I'm helping a friend put a 454 in his Biscayne. The motor is a 77. He is running a TH400 behind it. He thinks we can run any old GM flexplate behind it. I told him I'm 99% sure he needs to run an externally balanced flexplate. All the "research" I did tells me that pre 90 454's need a Externally balanced one. Am I right?? THanks, Todd

 

You have to run the externaly balanced flywheel. If not the motor will vibrate until you beat the bearings out of it.

 

Takes a special flex plate. Any 454 flex plate should do the trick.

 

If you dont use the right flex plate,,, you might break the crank.

 

Pre 90 454 were exteranlly balanced so you are correct. Paul

 

Also there was and may still be some people out there that built a balancing plate that is bolted to the crank flange so you could run any GM flex plate. They never seemed to me to work just right and just another h***le. Just get the correct flex plate... it won't break his bank account.

 

NEW flex plates are available from stock at most auto parts stores.

 

Ditto on all of the above!!!

 

Ditto on what Deuces said

Frank

 

Yes, they are still around and still not the answer...

 

Thanks Frank!

 

A bud of mine that was around hot rods all his life made this mistake: he used the proper external balance flywheel but failed to index it with the crank. You see, both items are not only drilled for the bolts but also for a dowel (or alignment) pin. The pin was missing and I guess he missed the point because they actually broke the bell housing on the turbo!!

Another point; the harmonic balancer also has some offset weight to it, so it is specific to a 454. Small block 400's have external balance also, but they use 400 specific parts.

 

good info to know, I have a 396 are like this 454 with the balancing?

 

Nope, 396's are internally balanced and use a neutral balanced flexplate or flywheel.

 

nope only the 454 is externally balanced, all other 396, 427 are internal

 

ATP #Z128. About $80.00 in Canada. Hope this helps

 

You could use the later 396/402 crank in a 454 block with 427 pistons/rings and use internal balancing stuff.

 

FWIW The GM part number is 14001992. 14" o.d., 11.5" bolt pattern and 168 teeth on the starter ring gear. This is a good p/n for up to 1990 usage.

 

Thanks to all!! Good info there. I had no idea that the balancer was 454 specific also.. I'm glad we caught this before it was together and we fired it up. That would have ****ed!! Todd