ConcoursMustang Forums

Restoring - General discussions that span across many different groups of years and models => Drivetrain => Topic started by: Morsel on January 02, 2022, 08:37:51 PM

Title: Are 64/65/66 C4 automatic flywheels stamped with a part number?
Post by: Morsel on January 02, 2022, 08:37:51 PM

I've been doing some digging and I thought mine was original to the car, but I'm not finding any part number, date code or anything on my 66 HiPo C4 automatic flywheel. When I search online or Ebay, even NOS examples don't seem to have any stampings. What's the opinion here?

Also, was there any difference in a HiPo C4 automatic flywheel and a standard 289 C4 automatic Flywheel?

Thanks,

Jason

Title: Re: Are 64/65/66 C4 automatic flywheels stamped with a part number?
Post by: 67gta289 on January 02, 2022, 09:30:45 PM

I've had about 10 or so over the last couple of years, and all I was able to find was FoMoCo stamped on the wheel, with one exception, as shown in the attached picture of a C6AZ-6375-B.

Now that's not a large sample size, but we have to start somewhere.

Title: Re: Are 64/65/66 C4 automatic flywheels stamped with a part number?
Post by: 67gta289 on January 02, 2022, 09:40:12 PM

As far as part numbers go, based on what I see in the MPC there was a lot of substitutions going on by 1975.  Here are pictures from the 1968 and 1975 versions. 

Consider this as for reference, but certainly not as gospel.

Title: Re: Are 64/65/66 C4 automatic flywheels stamped with a part number?
Post by: 67gta289 on January 02, 2022, 09:53:46 PM

Also did you check Mannel's small block guide?  May be covered, I don't recall.

Title: Re: Are 64/65/66 C4 automatic flywheels stamped with a part number?
Post by: J_Speegle on January 02, 2022, 10:40:00 PM

Quote from: Morsel on January 02, 2022, 08:37:51 PM

I've been doing some digging and I thought mine was original to the car, but I'm not finding any part number, date code or anything on my 66 HiPo C4 automatic flywheel. When I search online or Ebay, even NOS examples don't seem to have any stampings. What's the opinion here?

Also, was there any difference in a HiPo C4 automatic flywheel and a standard 289 C4 automatic Flywheel?

Don't have any pictures of a 64-66 C4 flywheel so can't confirm if the standard one does or does not have a stamped part number. Guess you have already looked through all of them for sale on Ebay

Yes they are different and at least the K code ones are marked

Here are a couple of examples

(https://www.concoursmustang.com/forum/gallery/16/6-020122213939-167212402.jpeg)

Title: Re: Are 64/65/66 C4 automatic flywheels stamped with a part number?
Post by: Morsel on January 03, 2022, 01:27:38 PM

Thanks you both very much, huge help. Guess I have to find a new flex plate :)

Jason

Title: Re: Are 64/65/66 C4 automatic flywheels stamped with a part number?
Post by: warwick on January 03, 2022, 04:40:48 PM

Over the years I have researched it and have come up with HiPo flex plate C4OE-6375-C, balance 30.4 oz compared to a LoPo at 28.2 oz.

You are on a slippery slope: the original torque converter was ink stamped AJ. There is ZERO external difference. The change was internal to allow about a 500 rpm higher stall so the HiPo would idle in gear with it's larger cam. It could have been a different fin angle ( most likely) or internal clearance modification.