69 L89 Flywheel/Clutch question

[Lynn S.]

Rebuilding a 69 L89 car that the owner said had the MA6 double disk clutch when he took it apart (old parts are MIA)....How do I determine if I have the correct flywheel and what replacement dual disk clutch would you recommend?? Thanks, Lynn Schwebach

[Dick W.]

Re: 69 L89 Flywheel/Clutch question

If it is a true MA-6 car the engine suffix code would be LU. I am not sure that I would want to spend the dollars to round up a complete clutch setup. It is not visible and you would not know the difference on the street

[Joe L.]

Re: 69 L89 Flywheel/Clutch question

Rebuilding a 69 L89 car that the owner said had the MA6 double disk clutch when he took it apart (old parts are MIA)....How do I determine if I have the correct flywheel and what replacement dual disk clutch would you recommend?? Thanks, Lynn Schwebach

Lynn----


The flywheel used with the MA-6 clutch cannot be used with other single disc clutches---it is not drilled the same. So, if the car currently has a single disc clutch, then the flywheel is not the correct one for a dual disc.

Furthermore, if the flywheel has GM casting number "789733", then I strongly suspect the flywheel is original to the car and the car was never MA-6-equipped.

The original MA-6 flywheel was GM casting #3963543.

What kind of dual disc clutch could you use? I wouldn't bother with one. Assuming the car was originally equipped with MA-6, any sort of aftermarket dual disc that you use now won't be original configuration anyway. Installing such a clutch may prove to be "technically troublesome" resulting in much frustration and grief. Plus, they're expensive. Not enough would be gained to make it worth it.

Externally, no one can see or know what clutch is installed, anyway.

[Warren F.]

Re: 69 L89 Flywheel/Clutch question

Lynn,

Those MA6 heavy duty dual plate clutch assemblies are very rare and unique. Zora Duntov's right hand man, Gib Hufstader invented that clutch. There are two different unique assemblies. The 427 internal balanced usage, and the 454 external balance usage.

My '71 LS6 Corvettes have this unique clutch. There are 5 unique pieces to these units. Your application requires these part #'s....flywheel 3955151, clutch pressure plate & cover 3959175, pressure plate (intermediary) 3955148, clutch discs (2) 3959176.

This clutch assembly was quite a bit ahead of its time. Very neat item to have, it goes well with K66 magnetic pulse transistorized ignition set-up and M22 heavy duty 4 spd transmission.

Dual plate clutch has 201 square inches of surface for clamping power versus the single plate set-up of 164.

Uses 1600 to 1800 lbs effective plate load versus 2450 to 2750 lbs for less leg fatigue.

A great history on this invention made for the '68,. '69 Trans Am racing years can be read in Camaro Racing: Untold Secrets by Wayne Gunn.

[Terry M.]

Re: 69 L89 Flywheel/Clutch question

While externally one can not tell if the clutch is dual-disk or single disk, a short drive is all one needs to tell the difference. The clutch actuating pressure is far less with the dual-disk than the standard clutch. It is about like the difference between the standard C3 clutch and the hydraulic actuated C6 clutch. As Warren stated the dual-disk was way ahead of its time and a real pleasure to drive.

[Warren F.]

Re: 69 L89 Flywheel/Clutch question

Dave,

I also first saw pictures of these clutches in the How to hotrod BIG- BLOCK CHEVROLETS by Fisher & Waar published in 1971. That's where I got interested in them.

I have a complete '71 assembly as a spare and recently sold two complete assemblies for '69 application.

The complete weight of this clutch assembly with flywheel attached is 52 lbs. I believe the single 11 inch clutch assembly with std flywheel is damn close.

[Joe L.]

Re: 69 L89 Flywheel/Clutch question

While externally one can not tell if the clutch is dual-disk or single disk, a short drive is all one needs to tell the difference. The clutch actuating pressure is far less with the dual-disk than the standard clutch. It is about like the difference between the standard C3 clutch and the hydraulic actuated C6 clutch. As Warren stated the dual-disk was way ahead of its time and a real pleasure to drive.

Terry-----


There's no doubt that the pedal effort is less than single disc set-ups. There's also no doubt that the clamping force is greater. However, considering the usage that most folks with cars of our vintage experience, I doubt that the dual disc offers much practical benefit.

The single disc, 14" clutch otherwise used for 1969 L-89 applications is exactly the same as the clutch originally installed (and subsequently replaced) in my 1969. I never found the pedal effort to be that uncomfortable or "trying", at all.

One other thing: it might be surmised that GM dropped the dual disc clutch due to cost. However, GM used some very expensive clutch set-ups in the years following the last use of the dual disc in 1971 (ever purchased a flywheel for a 1992-96 Corvette?). However, they never went back to a dual disc set-up for any application I'm aware of. So, dual discs were used in a total of about 250 Corvettes ever made.

[Lynn S.]

Re: 69 L89 Flywheel/Clutch question

Thanks to all for the info and advice.
This car has the LU engine suffix but after further investigation I doubt it had the MA-6 clutch setup. Took the flywheel off last night and found casting number 3789733, H8 *8, GM12. Sooo, based on this info and your suggestions I will order a single disc, 14" clutch, live with the slightly stiffer pedal and move on to the next problem in this restoration.
Lynn Schwebach

[Terry M.]

Re: 69 L89 Flywheel/Clutch question

My only point was that there is a very different feel to the clutches -- in fact the three different clutches all have a different feel to them. I guess I should count myself privileged to have driven at least one of each -- and a couple of those 250 dual-disk units. There are some advantages to having been around when these were just another used car.

[Joe L.]

Re: 69 L89 Flywheel/Clutch question

My only point was that there is a very different feel to the clutches -- in fact the three different clutches all have a different feel to them. I guess I should count myself privileged to have driven at least one of each -- and a couple of those 250 dual-disk units. There are some advantages to having been around when these were just another used car.

Terry----


Yes, there's definitely a difference in feel between the various types of clutch systems discussed here. For me, I really think the 66-81 11" clutches have the best feel of all. Yes, they do have higher pedal pressure but I think they give better "feel". I definitely like it better than the hydraulic clutch in C4's, C5's and C6's. I'm not too fond of those, at all.