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I wonder if that new shaft would work with what Simard came up with for using Tilson TO bearings and disks and pressure places. He made a Flywheel that would accept. Wonder if they are made for similar disks, etc.
Great Stuff greg.
The clutch discs are a brand new product for Tilton, way after Mike retired.
I made (Aasco made) several flywheels for the 7.5" Tilton clutches, which is what I think Simard did. Pretty severe clutch for street use....pretty much on or off. Fantastic on the track...the light 7.5" discs are super easy on synchros and make shifting very quick. (Still have one, if anyone needs a dedicated race clutch.)
Thx for the answer Greg! After the discontinued intermediate plate it‘s difficult to maintanance the Dual Disc clutched Cars.
Used Parts are broken and I and a lot of People in the 928 scene need a Plan B.
Thx for the answer Greg! After the discontinued intermediate plate it‘s difficult to maintanance the Dual Disc clutched Cars.
Used Parts are broken and I and a lot of People in the 928 scene need a Plan B.
The dual disc clutches have needed a solution, for a long time....they are complex, difficult to make work properly, the pieces are expensive, the flywheels are, by and large, cooked and need to be replaced, and the intermediate plates are, for the large part, junk.
The problem with anything new made for the 928 is the cost of making the pieces.....always has been. Because the market is so tiny, we are limited in the quantity of pieces that can be built at any given time. In the quantities we can afford to inventory, the cost of production is very high, which drives the cost of each piece sky high.(Just an example, it costs $300 to heat treat 5 clutch shafts or the same $300 to do a pallet full of clutch shafts. So, building 5 shafts at a time makes the cost to heat treat, per item, $60. If I can build 20, the price, per item, drops to $15. If you can do 50, the price is $6. Big difference!)
My hope is that demand will be high, which will significantly reduce the production costs, and I can get the customer price down to ~$3,000.
Got about 2/3 of the way through the new clutch install today, headed back to Greg's tomorrow to finish up, hoping the damned day job does not interfere.
Custom flywheel, with added lightness. Headers had to be loosened, to get the flywheel up into the bellhousing with the steel starter bracket in place. .
Clutch pack loosely in place, buttoning to re-commence in the AM.
Greg, please keep me informed as you investigate the early car applications. My supercharged '79 has been upgraded to the '83 dual disc clutch, but to hold the torque from the blown motor I'm using a 928MS friction disc setup that I think they may only make for Carl and it's almost like the discs are sintered metal. It doesn't slip though !
Needless to say, they're very grabby when engaged if the car is stopped and they don't gently engage with the flywheel well because there's not Marcel springs and no sprung hub. I tried some OEM friction discs when putting rur powertrain in initially and and the engagement action was so much nicer, that is until I hit the boost - checked the mirror to look for 2 nice black stripes that weren't there and knew the clutch was slipping from the torque. Went back to the special Spec discs
From a driving enjoyment perspective the clutch action is one of the last remaining things I need to address on the Spyder and this new clutch mated to my Z06 6-speed trans sounds like an ideal combination.
If there's enough interest, might you look at doing a group but to keep some of those finishing costs down.
Hey Greg are there any plans to make these available for the '86 cars? Just got a new clutch put in this year (with your clutch hose) and fortunately for me the intermediate plate passed inspection (I took it off the road the second it began to slip and grandma'd it to the shop)...the engine has an exhaust, no cat, Porken's chips, the upgraded airbox temp sensor, your alternator, new coils and plenty of vacuum...so hopefully plenty of life for the standard clutch but I don't have plans to get rid of the car anytime soon so another clutch is absolutely in its future...
Here's something fun: When neither the starter nor the clutch slave are hung off the lower bellhousing cover, then the cover becomes just a cover. And everything works without it:
I am thinking of an animated GIF that will probably get us banned...
So I promised some 3D layout drawings... The immediate question with this clutch was whether it would fit into the bellhousing, it is not a 7" race clutch for which the answer is obvious. My first guesstimate was "no way", the paper/plywood cutout was "maybe but...". I've done a lot of drafting and 2D CAD, but that was no better than the paper cutout. So I dove back into 3D and modeled the clutch housing, at least the parts that had to fit:
That looked good, especially the mag-lev-suspended starter ring. But the starter ring was in the same place as the factory starter ring and that fit, so no problem there. The question of how it actually got attached was for the experts.
The next question was the offset from the crankshaft, and at this point our GT was down south. So Rob kindly provided a precision measurement from the crank surface to the bellhousing mating surface. (And no, that is NOT our GT engine):
Cool! Now all we needed was the shape of the bellhousing. The good news was that our bellhousing was down south with the GT, and Rob also happened to have a precision 3D scanner. Seriously, it really is a nice scanner. The only problem is that any scanner struggles with shiny objects, something about reflections causing confusion as to where the surface really is. And Greg had cleaned up our bellhousing, it was nice and shiny.
So Rob scanned the bellhousing, I deleted most of the reflections that were in the next room, and combined that with the clutch pack and phantom starter-ring:
Viola! It fit!! At least as well as it did on paper and plywood. That was enough to proceed for the first one at least, and the smart guys figured out how to attach the starter-ring, connect it to a Porsche drive shaft, and a bunch of other not-obvious stuff. And sure enough: When it came to putting together metal parts, it fit! And worked!!
Thank you Greg, and thank you Rob!
Last edited by jcorenman; 12-21-2019 at 01:55 AM.
Reason: More pics
Greg, please keep me informed as you investigate the early car applications. My supercharged '79 has been upgraded to the '83 dual disc clutch, but to hold the torque from the blown motor I'm using a 928MS friction disc setup that I think they may only make for Carl and it's almost like the discs are sintered metal. It doesn't slip though !
Needless to say, they're very grabby when engaged if the car is stopped and they don't gently engage with the flywheel well because there's not Marcel springs and no sprung hub. I tried some OEM friction discs when putting rur powertrain in initially and and the engagement action was so much nicer, that is until I hit the boost - checked the mirror to look for 2 nice black stripes that weren't there and knew the clutch was slipping from the torque. Went back to the special Spec discs
From a driving enjoyment perspective the clutch action is one of the last remaining things I need to address on the Spyder and this new clutch mated to my Z06 6-speed trans sounds like an ideal combination.
If there's enough interest, might you look at doing a group but to keep some of those finishing costs down.
Here's what the current setup looks like.
I understand, completely...which is why I built this.
This clutch is so smooth, it's just incredible.
Just to be sure that Jim Corenman's was not just a fluke, we installed one into Rob's car yesterday and today.
Butter smooth. Rob's car didn't have the clutch "helper" spring, like Jim's. The "pedal pressure" is higher than a stock clutch, but not terrible (Jim did the math and it requires 50 pounds of force.)
Your car is the perfect candidate for one.....
exactly my "target market" for the dual disc version.
And I'm not convinced that a flywheel without crank trigger capability would be a good investment, for anyone that "needs" the dual disc version. I'd suggest that anyone who is making big horsepower might want to go ahead and use a 60 minus 2 flywheel....just in case you ever decide to put aftermarket injection on the car. Sure not going to hurt anything to have the "teeth" there...just in case. And the weight and cost savings will be very minimal.
I think all you would need to install one would be an '89 to '95 bell housing.....from either an automatic or manual car.
12-18-2019 | 09:05 PM
