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Old 06-11-2020, 11:34 PM
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Default Flywheel 101

I acquired a '64 389 to replace the '66 in my 1964 GTO. It lacks a flywheel and clutch assembly. I read that the '64-'65 is a unique design. Is this true and what do you recommend for a daily driver? Are there advantages to increase to an 11" clutch or will this cause clearance issues with the bell housing?
Performance flywheel manufacturers warn of clearance issues if running a stock clutch assembly. I don't understand. Are new original style flywheels even available?
Again, the engine will be built with reduced CR for a daily driver.

Thank you

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Old 06-12-2020, 02:28 AM
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Depends how much the engine is built. The 10 3/8" (stock) clutch works pretty well. As to flywheels, they are the same from '64 until into the 70's when they changed the size of the flywheel flange. You don't want a stock flywheel. An aftermarket steel wheel is better. Depending on your engine and gearing, I suspect the 30# steel flywheel would be good. The stock flywheel was 40#. If your geared for racing the aluminum flywheel is good, but it spins the tires easier from a roll on the street. I have the 11" clutch on mine, but I don't have a stock bell housing.

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Old 06-12-2020, 10:34 PM
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Thanks OMT. I'll be running a stock 389 tripower with 3.23 gears. I did not realize the weight difference of the stock flywheel. Looks like an after market unit is the way to go. Thank you

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Old 06-14-2020, 12:42 PM
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I have an NOS-GM flywheel 9779232 still in the GM box. 10 1/2" as they were called. 1965-1975
It weighs 30# on my bathroom scale.

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Old 06-14-2020, 12:49 PM
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In the GM-Pontiac parts book 64 has a different part # than 65-75.
No idea what would be different about it. Bet someone knows.

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Old 06-14-2020, 04:19 PM
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Paul Z's. Restoration Guide states '64 & '65 flywheels were different but not why or how. Maybe just different p/n. 1964 p/n 9773498.

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Old 06-14-2020, 06:03 PM
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Took the cast iron stock one off many many years ago and installed a Aluminum flywheel.
Never had any vibration, drive issues and it gave me excellent life for many years.
Believe it was made by WEBER. That being said, on my 64 GTO I have never had a issue with flywheels. Possibly the 64 Big Car flywheels were different.

Tom V.

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Old 06-14-2020, 06:11 PM
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Tom,big cars had bell mounted starters and had flywheels with the ring gear in diff location.Tom

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Old 06-15-2020, 02:50 AM
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The billet flywheel rings like a bell when you tap it with a hammer. The cast iron is just a thud. If you have ever seen a clutch or worse flywheel
explosion aftermath you will appreciate a scatter shield. And, I used to race my 62 bare foot for better feel of the pedals and such. Youth?
My brother exploded the clutch on his 64 and I was in the car. It shattered the bell housing. A 37 Chevy they were building had a huge
gaping hole over the trans and bell housing. I was just a kid but used a metal realtor sign to fashion a cover for it. Well, they blew up the
clutch in that one. It shot metal out one fender and up through the hood as well. My feeble effort probably saved them some grief.

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Old 06-15-2020, 11:26 AM
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Quote:
Originally Posted by tom s View Post
Tom,big cars had bell mounted starters and had flywheels with the ring gear in diff location.Tom
And different part numbers for 64 P8 and T8.
Looks like 64 was 1 year only ?
Bellhousing too

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1st time on a dragstrip, 1964. Flagstart !

"Thanks for the entertainment."

"Real Indians Don't Wear Bowties"
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Old 06-15-2020, 01:56 PM
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Not sure why a 64T8 and 65T8 would be any diff?64P8 and 65P8 forsure are.Tom

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Old 06-16-2020, 07:33 PM
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My 64 flywheel weighed 40#, so I just assumed the 65's did also. That must be the reason for different part numbers.

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