The stock dual disc clutch will hold 500 crank hp (~420rwhp) just fine. I was just doing some testing on my "closed race course" If I tried to do what I just did with my old single disc clutch, it would roast. Even at 3,700RPM where I am making just over 8psi instantaneously the clutch grabs perfectly. I also have a pressure plate that is 50% stronger in the event that I manage to run into a 2.2 or 2.4 liter autorotor. You should be able to get over 450rwhp with a 2.0 and some work, and I would try the stock DD clutch with that configuration to see if it will hold before upgrading.

Dan
'91 928GT S/C 475hp/460lb.ft

 

Can you share some details on this? Is it a modified stock PP or something else?

 

I thin this is the same clutch as the '85, a direct fit.

 

Mark Anderson sent out a stock DD PP for me to have it modified with stronger springs, not sure how much stronger %-wise it ended up vs stock, but it has held up fine with the stroker so far. The bill for the mods was $250.

 

I think mine is a 2.0, it was the next progression that DR was going to do, it is bigger than any of the DR kits out there right now, it may be a 2.2.

How can I find out for sure?
Might be a good thing for me to know for sure.

Thanks for the info on your clutch, did Mark A do the upgrade on that pressure plate, or did you have it done here in Atlanta.
Did you notice any increase in pedal effort?

I have another full DD clutch set up, I may send it off to have the pressure increased.

 

I have a pressure plate modified by Mark just like the one in the picture above that Rob posted. I thought I was going to need it, but it has been over a year and 12k miles and no issues with the stock parts. On the S/C there should be a plate with an OA or MX number and serial number. What does yours say?

Dan
'91 928GT S/C 475hp/460lb.ft

 

Yes ...."Relining the disks is easy. Every city will have a shop that does this....."

Correct BUT they must understand that the discs can not be too thick or you have major release issues and dragging which plays hell with the trans gears and syncros.

 

Mine is still in the plastic bag, and I can not seem to find a plate or any numbers, where would they be located?

 

We love our rare exotic "handmade" super cars, the "flag ship" of their Era....until we need Porsche parts !
Why would they NOT be expensive ???? Need a motor for your Boxster, someone said they are around $12,000 now which is more than many of those are worth. The GT2RS I was fortunate enough to drive listed for $250,000 and he paid anothe 50K for the right to buy it....how much are his carbon rotors ??? Parts for ALL Porsche cars are expensive. The only cheap part of 928s is the real low resale value for the average car....
Labor is going to be about the same as the dealer, over $120 per hour in most areas, for someone who really knows ....The dealer techs of course would rather be working on clean new cars under warranty than an old 928 where more times than not the needed repairs are "too much"..... so just fix it a little so I can drive it. Often followed by "I am just going to sell it anyway".

 

Usually across the front or side... however some are unmarked so it may be more difficult to I.D. I'm sure Dave would know though.

Dan
'91 928GT S/C 475hp/460lb.ft

 

Thank you.

 

The diameter of a clutch has a great effect on the speed in feet per second that weight near the outer edge is traveling. At a given RPM say 6,000 the circle which weight is traveling is much greater the bigger the clutch flywheel assembly. Since Kibort's E = M C squared, there is more stored energy and it goes up geometrically. The net effect on acceleration in gear is relatively small but HUGE when you wing it out of gear or blip for upshifts, downshifts..... and it sounds really good too