Clutch type 1966 427/425HP

[Tom L.]

I'm going to have my original motor pulled and rebuilt--I'd like to replace the clutch at this time and looking at the clutch types how do I find out whether mine is a:
Clutch Kit. 10.5- 10 Spline 327/350/396 & 427 w/HD or a Clutch Kit. 11- 10 Spline 350 & 427 w/o HD ?
This 2 clutch type are off of Corvette America's web site. Anyone?
Thanks
Tom
Member # 51574

[Edward B.]

Re: Clutch type 1966 427/425HP

Tom, if you haven't already done so, download the 1966 CORVETTE SPECIFICATIONS from the GM Heritage Center. It has all the info you need about your car.

That being said, the L72 originally came with a 10.5" clutch, but in the 50 years your car has been around, it's impossible to say what's actually in there at the moment! My recommendation would be to pull the clutch and measure it BEFORE purchasing a new one.

Ed

[Tom L.]

Re: Clutch type 1966 427/425HP

Thank you Ed.

[Larry M.]

Re: Clutch type 1966 427/425HP

I agree that you need to actually see what your car has installed, but the 1966 BB cars came from the factory with an 11 inch clutch. The only exception was perhaps a few "special race cars"......(early L88 cars). These had the 10.5 inch HD clutch.

Larry

[Edward B.]

Re: Clutch type 1966 427/425HP

That's funny Larry. That's what I thought too, but the specs on the heritage site shows 10.5" so I figured Chevrolet would know better than I would!!

Ed

[Joe L.]

Re: Clutch type 1966 427/425HP

That's funny Larry. That's what I thought too, but the specs on the heritage site shows 10.5" so I figured Chevrolet would know better than I would!!

Ed

Ed------


Well, they're wrong on this one. 1966 L-72 might have been originally scheduled to be equipped with the HD 10-1/2" clutch (i.e. like 1965 L-78) but I don't think any were actually built that way. I would not rule out the possibility, though, for very early cars. If so, though, I would expect different suffix codes. Curiously, there were 2 suffix codes for 1966 L-72.

In any event, it's easy to tell what clutch needs to be installed assuming that the bellhousing is original to the car. If it's a GM #3858403, then it takes a 12-3/4" flywheel with 10-1/2" clutch. If it's a GM #3872444, then a 14" flywheel with 11" clutch is required.

[Larry M.]

Re: Clutch type 1966 427/425HP

That's funny Larry. That's what I thought too, but the specs on the heritage site shows 10.5" so I figured Chevrolet would know better than I would!!

Ed

I may be how they are measuring the disc............perhaps to OD of the friction material. Notice that the SB cars are shown at 10.0 inches.

The disc itself is often a bit larger than the friction material.

FWIW.

Larry

[Keith B.]

Re: Clutch type 1966 427/425HP

Also there is no need to mail order this part. Any good parts store can get you a clutch.

[Edward B.]

Re: Clutch type 1966 427/425HP

I think you guys might be on to something but the published numbers don't compute.

The 1965 Corvette AMA specs for ALL engines shows the clutch facing to be 90.7 square inches, which would be a 10" clutch. However, the date on the AMA specs is 9-28-64 so the L78 isn't listed, and I don't believe ANY V8 Corvette EVER came with a 10" clutch!

The 1966 Corvette AMA specs (published 10-7-65) for the 427 engines shows the clutch facing to be 103.5 square inches, which would be a 10.5" clutch. This is the one in question.

The 1967 Corvette AMA specs (published 10-7-66) for ALL engines shows the clutch facing to be 123.7", which would be an 11" clutch.

So like Joe said above, more than likely the published figures for 1965 and 1966 are incorrect, but I'd love to hear what original 1965 L78 owners and original 1966 L72 owners have to say about their clutch sizes.

Ed

[Joe L.]

Re: Clutch type 1966 427/425HP

I think you guys might be on to something but the published numbers don't compute.

The 1965 Corvette AMA specs for ALL engines shows the clutch facing to be 90.7 square inches, which would be a 10" clutch. However, the date on the AMA specs is 9-28-64 so the L78 isn't listed, and I don't believe ANY V8 Corvette EVER came with a 10" clutch!

The 1966 Corvette AMA specs (published 10-7-65) for the 427 engines shows the clutch facing to be 103.5 square inches, which would be a 10.5" clutch. This is the one in question.

The 1967 Corvette AMA specs (published 10-7-66) for ALL engines shows the clutch facing to be 123.7", which would be an 11" clutch.

So like Joe said above, more than likely the published figures for 1965 and 1966 are incorrect, but I'd love to hear what original 1965 L78 owners and original 1966 L72 owners have to say about their clutch sizes.

Ed

Ed-------


There are quite a few inaccuracies in the published AMA specs. While it might SEEM like they ought to be authoritative and accurate, that's not the case. I've learned to be skeptical about anything in them. I think what happened is that this information was sent to the AMA very early for each model year and before the actual PRODUCTION configurations were finalized. No later attempt was made to correct such resultant inaccuracies so they persist "forever".

There were LOTS of Corvette V-8's made with 10" clutches. This includes ALL 1957-62 Corvettes with manual transmission.

[Edward B.]

Re: Clutch type 1966 427/425HP

There were LOTS of Corvette V-8's made with 10" clutches. This includes ALL 1957-62 Corvettes with manual transmission.

Sorry Joe. I meant to say any C2 Corvette. And you're right. The AMA dates are late September or early October of each model year.

Ed

[Richard M.]

Re: Clutch type 1966 427/425HP

I go to my local NAPA store for clutches as they source the LUK brand. Recently installed the NCF 1104049 in a 427 and it's working fine.

Add your vehicle data in the MY Vehicles tab......and "clutch set" in the search tab.....

http://www.napaonline.com/napa/en/se...ext=clutch+set