Portly

Hi all

While I have the engine out of my 951, it seems like the perfect time to do a clutch swap. A review of the service records for this car indicates no sign that it's ever been done - or at least not in the last 60,000 miles - so it seems like now would be a good time to take advantage of having the engine out.

I guess I have two seperate questions: First, does anyone know the torque-handling ability of the "stock clutch / 930 disc" setup which is so popular? Second, any recommendations on a clutch that can handle roughly 350 lb/ft of torque? (Or 300 Wheel Lb/Ft, if you prefer to think in those terms...)

I'm looking for a setup that's pretty easy to live with, but has some reserve capacity beyond the stock engine's power output. I don't yet know if I'll ever even increase the power output of the car, but if I do, I'd rather address that now.

Also, one more semi-related question: Anyone have a list of "other parts to replace while doing a clutch job"? I've seen kits which include just about every bolt and bearing associated with the clutch - is this necessary, and if so, are there other items I should be looking at too?

Thanks much to all of you for helping out a 951 newb.

_Jeff

eclou

clarks' garage website has a nice write up and discussion of what else to do at the same time. Unfortunately, that list is infinite, because you might as well do x then y and why not z and if z then perhaps q.......

WesM951

I would suggest at least the Cup Clutch Kit. It removes the 6 small springs that are prone to failing in our stock clutch disc's and is able to hold more power as well.

The biggest thing to change while you have the clutch out is the rear main seal.

mtnman82

You might want to check out this thread I started - along the same lines of what you're asking on the clutch:

https://rennlist.com/forums/944-turbo-and-turbo-s-forum/282374-fidenza-or-lightened-stock-flywheel.html

Charlie944

I would upgrade your Pressre plate to either a KEP which is a nice chunk on change or what I did was send my PP to Markus Blaszak and he modifies the fulcrum points to increase leverage by 30% This however reduces the clutch pedal travel, but it actually is nice combination with a short shift kit. I had this PP and his Stg 3 windowed Kevlar disc and after one track day it was toast! Perhaps I did not wait long enouth before break-in (450miles) but since then I have upgraded to a full-face Feramic disc from South Bend Clutch company. This disc with my 30%+ PP is good for 450ft/lbs torque. Granted I still use the 225mm size clutch so a 240mm clucth that the 951 uses will be good for more holding capacity. Torque is the true determiner for a clutches holding capacity not horsepower.

There is a simple formula for calculating the torque capacity of a clutch. The formula that is used is T = N x R x F x P. Defined as:

T = torque capacity in ft. lbs.
N = number of friction surfaces (single disc is 2)
F = coefficient of friction
P = lbs. of pressure plate clamp force
R = radius of gyration in feet (.308 for a typical 225mm clutch)

The math for R is (OD + ID) / 4 = Average radius of the disc,then convert to feet.

I then divide the final product by 2 and you have your number.
The Feramic disc I use has a coef of friction of .70 which is higher than Ceramic and much more slipable. If you supply your old disc to South Bend they will rivit the new material onto the disc for a pretty reasoable price...talk to Andy Slessman.

Lindsey Racing sells a nice package kit w/ new bolts, rear main seal, guide tube, pilot bearing, and fork bearings for 65$.

Markus Blaszak
Blaszak Precision Motorsports
4835 Holmes Road
Inverary, ON, Canada
K0H1X0
613-353-7012 EST
www.BlaszakPrecision.com

Let me know if you have any other ?'s... hope this helps!

chrly924s

This guy has a helpfull write up.
http://home.hvc.rr.com/nine44/Kehr%2...eplacement.txt
I just got my clutch kit in from Vertex (my racing days are over) And Paragon has a nice "kit" with most everything you need for just the clutch.
http://www.paragon-products.com/product_p/951cak.htm

Portly

Thanks everyone for the feedback and suggestions. Very much appreciated. The links are great as well.

I'm still hoping someone can give a rough estimate on the capacities of the "930 disc" setup that Paragon sells, but these other options are good to know about.

Edit--- Nevermind that last request, the link that mtnman82 posted has lots of good info on this.

Thanks all for the help.

_Jeff

Charlie944

Jeff, the 930 disc is a tad thicker and IIRC has a bit more surface area but we are talking less than 10% more. In the end it is still a Organic faced disc so the holding capacities with a stock pressure plate is not going to be much more than a stock clutch. If you upgrade to a KEP 1 or 2 then the PP is doing the majority of the work of holding your additional power. If you opt for a stock PP or a modified one like I suggested then you should look at some more aggressive disc compounds with increased coefficients of friction.

Portly

Charlie 944 - thanks for the clarification. I've been reading other threads this afternoon (dunno why I couldn't find them before) and have concluded that the 930 disc setup is primarily a way to reduce cost a bit and extend the disc life, thanks to more material in the disc. But thanks for backing that up.

I just noticed you put the above reference in your first post. You'll notice I never mentioned horsepower in my posts. As you've pointed out, clutches don't "see" horsepower - torque is what makes them slip.

_Jeff

Charlie944

Jeff, I did notice that and I threw that in there for others that may be reading. I am glad I can help and no problem about keeping me in check I have done two clutch jobs by myself with no lift and I would hate for you to go through the same thing by making an uninformed decision. I would try and go with a setup that can handle 50-75 ft/lbs above your current (or more importantly) future goals for the car...if you have any.