[stone7777]

Can someone tell me the correct Flywheel size for a 389 335 hp engine?

[John V.]

Do you mean the outside diameter, or the register diameter?

Or the clutch diameter?

I don't have one to measure, but the O.D. of the flywheel I believe is right at 14".

The ring gear is 166 tooth and press fits to the O.D. of the flywheel.

The flywheel mounts to the back of the crank, registering on the flange dia. which should be right at 2.75".

This is only useful to know when comparing to late '70s cranks which had a smaller flange at 2.50". Can't mix and match the flywheels on those.

The clutch was always described as a 10.4" dia. Borg & Beck style.

I'm sure there is a thickness dimension and probably some guideline limits for refacing the flywheel surface before it should be replaced but I don't have that info.

The '65 Flywheel was same p/n for the big car and Tempest V8. Same flywheel was carried over to '66 also and maybe beyond. Only exception, there was a specific flywheel for the '65/'66 big car Heavy Duty clutch. I believe this was an 11" clutch, I suspect the only difference in the flywheel was the drilling/tapping for the larger dia. pressure plate. Aftermarket Pontiac flywheels might be drilled for both patterns, I sure don't know.

I am no expert on flywheels, don't know if my answer is helpful at all. But you might get more response if you explain why you want to know about the flywheel. If you are having fitment problems, somebody here will surely be able to help figure it out.

[stone7777]

John.

The flywheel and clutch set up is missing from my new motor.


I was looking at Summit to order a new flywheel.

I thought it was wise to ask in advance.

They do list a 166 tooth unit.

[stone7777]

I am confused, Napa and Advanced Auto all list the flywheel at 168 teeth.

But, Summit lists it at 166.

Would 168 tooth not work with the starter?

[John V.]

Will need an answer from someone smarter than me.

Was pretty sure 166 was correct. Could 168 be a late model ('04-'06 GTO)? Or maybe it doesn't matter to the starter. But I sure don't know. Sorry.

[goatman65]

I'm thinking that the 168 tooth is for sbc. Could be the listing is for the later model corporate engine cars.

[66 Gas Tires Oil]

make sure you get the right balance the less expensive ones are internal balance. also the Mcleoud flywheel i got had a ring that you knock out to fit the larger crank. In the clutch world bigger is better. get the bigger one.

Jim

[wmurrell]

Took a look at a flywheel I removed from a ’65 GTO back in the late ‘70’s. Car still had the original 389 motor, but unfortunately had been wrapped around a telephone pole.
The gear ring on the flywheel has part number 8621677 stamped on it. It is dated C 5 (March ’65). I counted 166 teeth on the ring and you can see the bolt pattern in the attached photo. I looked in a ’66 Pontiac Parts Catalog and it shows the same flywheel/ring for ’65 & ’66.

Bill