Hi all,

Just came into a relatively good shape double disk clutch and am thinking about using it for my GT. Did a quick search, but didn't find any really concise posts...Are there any sites out there documenting the conversion?
What parts do I need aside from the clutch pack to complete the setup? I have a complete good shape stock 89 clutch...(spare) as well as the new one I put in about a year ago...Do I reuse the stock 89 release arm/release bearing etc and mate it to the dual disk, or do I need other specific model year parts.

I know I need to change the flywheel. I have heard a 87 AT flywheel works..but what needs to be done?

Thanks in advance..

Tom
midlman@rennlist.net 89GT

P.S. I noticed that this double disk set up was balanced to the flywheel in the car it came in.....Is it a standard procedure to get they flywheel and clutch pack spin balanced before mounting?...or can it be a bolt in and go type setup.?

 

Tom

You need the 87 atuo flywheel and a 85 S2 manual flywheel and you fit the timing teeth off the 87 onto the 85 fly and i'm not sure if you need the clutch master cyl off the 85 aswell.

Its a job i will do but there is a lack of 85 maual flywheels over here in the uk


Stuart

GT UK

 

Tom,
It's been a couple of years since I did this but from what I recall: Besides the later timing teeth on the earlier flywheel, the earlier release arm, bearing, and guide tube must be also be used, together. My write-up which is not quite 100% is too large to attach, but I'll e-send if you'd like. At the time I bought the double disk retrograde as a kit from Devek.

Good luck...

 

also need the earlier starter mount bracket.

 

my 81s with a double disk clutch has a GTS release arm. The old one was bent and it took a couple of attempts before I got the correct new one. Consequently I don`t believe you need the early release arm.
However i was not around when the Previous owner made this upgrade to the release arm so I don`t know what (if any) mods had to be made.

 

AFAIK the only throw-out bearing available is the GTS bearing. AND the GTS bearing requires the GTS release arm and the GTS guide tube. The ID of the bearing is 1mm larger than pre-GTS - thus the new guide tube and the OD fits only with the GTS release arm.

 

I'll take the write up...email it to midlman@rennlist.net

Hoping I don't have to spring for many new parts....so far it sounds doable relatively cheaply, but if it starts going up in cost...i'll just stick with the stock one...and spend the money elsewhere .

Thanks,
Tom
midlman@rennlist.net
89GT

 

from memory, as we did this with my car (the holbert racer)

as was said, 85 flywheel and 87 auto timing gear ring. (but they need to be spot welded in the proper position)

then,
2. used a early model bell housing. we used this for better accessability of the starter, and removal of a starter bracket that is not then needed (extra 3lbs weight)
2a. you then also need a new clutch slave cylinder. keep in mind that now your flywheel lock will be the older style when it comes to timing belt change time.
3. used a standard clutch kit and found an ole intermediate plate in my attic from a clutch job on my old street 84 way before i even thougth of racing,and it was in perfect shape. (still in there today) (knock knock)
3. maybe the intermediate shaft and bearings too. all the mechanical stuff was the same
4. also, have to make a grind on the bell housing as the gear teeth on the flywheel hits slightly. dremel or grinder does the job quickly. definitely needed on the early bell housing, dont know on a later one.

plan to have more grip, and 25lbs less weight of rotating mass!! (dont ask me how much HP you save, or we will have a 200 post debate again. simply put, it depends on rates of acceleration. ie, the quicker the engine revs, the more power saved. over a 6-9 second dyno run in 4th gear, it aint much. however in first, it is more and certainly its on the car, and thats nice to remove anyway you can)

MK

 

i thought the double disc clutch had more weight not less?

 

Tom don't do it, better sell it to a friend at the same price you paid

 

less weight and a much smaller diameter too.

mk

 

How much less? They both feel incredibly heavy when taking of or installing under car.

 

Absolute weight may no be not the relevant issue. The issue is weight (mass) times distance squared from the center of rotation. The twin disk clutch is smaller in diameter no?

 

with the flywheel, the enire stack i measured to be 44 lbs for the S4 and 22lbs for the '84ish.

Im going off memory, i have a jpeg of both stacks on a scale, and it was a 20+ lbs diff for sure.
MK

 

Yes, so not only is the dual disc clutch lighter , it is smaller diameter, helping on two counts.

mk

the weight wouldnt have been the relative issue, if there was more of a change in diameter and less of a change in weight between the two.