odonnell

I'm trying to decide on a clutch for my 951 project. Here are my main criteria:

- Hold 400-450 ftlb

- Be able to use a 60-2 trigger flywheel

- Not going to overtax the clutch fork and lead to doing the job all over again


So far there are 3 options that stand out to me.

Option A) The tried and true KEP1 pressure plate and either a cup disc or equivalent. The aftermarket 60-2 flywheel for the 951 will work. Seems to be relatively easy on the fork compared to other options (KEP2, etc).

Option B) the SPEC line of clutch kits from LR. Same flywheel used as above. I'm having a hard time finding field reports of how clutch forks are holding up.

Option C) Push type clutch from LR. While this gets me away from the clutch fork altogether, I would need to get the kit designed for the 16v models, as the normal 951 kit comes with a custom flywheel due to geometry requirements. This flywheel is available with a 60-2 trigger but only for the NA-sized clutch kit.


With these options, I'm interested in opinions. Cost is somewhat of a factor but I would rather get the most fit-for-purpose parts than spend 2 weekends redoing a job.

NCLA951

steven74

I am also leaning towards option a. I think there is also an option of getting a used cup clutch relied with feramic material or similar as well. I see zims sells an upgraded blazak type clutch fork on exchange.

NCLA951

steven74

As per an older post on the "other" forum, it appears that is what Blazak does to the clutch fork. Essentially clean and rebuild tips and possibly replace bearings with bushings. I don't know how much room there is for adding gussets or other strengthening parts in such a compact area.

951and944S

Considering that most all auto manufacturers used stamped steel clutch forks with a ball pivot as it's hinge point (read massive friction), the 944's very rigid cast piece with twin needle bearing pivot is about as good as it gets in a stock configuration.
Go to a parts counter and ask for a throw out bearing for XX model push clutch then look at a 944 bearing.
The quality is night and day.
In general, push clutch release bearings are centered only by the pilot snout and loosely held by the fork.
It's impossible for the bearing to remain centered on the diaphragm springs without the ears of the bearing moving on the loose fit of the fork because of the arc of lever movement, more friction, more wear.
The 944 has the piloting snout as part of the bell housing but the bearing is also retained onto the diaphragm by spring/shims/lock ring.
I don't see what all the hype is about switching to a push to release diaphragm when it means sourcing conversion parts or buying a costly "kit" for little to no gain.
Technologically, it seems to me, reverting back to 1930's is a non starter.
(Yes I'm aware of slave/bearing combos, just another point of unnecessary and hard to replace failure)

My $.02

T

V2Rocket

if you're up for an experiment...

the fork fingers get wear because the TOB is spinning against them.
most cars the TOB stays still relative to the fork and only moves in/out with the pressure plate. so we need to find a way to secure the TOB to the fork...

and it just so happens that a 996 turbo uses the same diameter clutch package as a 951, and the TOB appears to be similar size and attachment style (pull type with shims and stuff), but the 996T TOB has little nubs for the fork to hang onto...

now, a 996T fork is no good, but there may be something else out there suitable.

odonnell

Thanks for the feedback. A Texas 944 buddy who is a professional welder (AK951 on here) is reinforcing my clutch fork and I have sintered bronze bushings to press in. He and I beta tested these bushings on his 951 and they are working awesome.


T, the fork issue is unfortunately documented pretty well enough that it's causing me tp second guess clutch choices. The same guy above had his fork break and I know a few other guys who had similar failures. By the way, seen you're in Louisiana, I'm down in Broussard for a few weeks for work. If you're driving through let me know if you want to grab a beer.

Paulyy

Spec clutches use the OEM Scachs PP.
Porsche also are making clutch forks again.

V2Rocket

OT but have you ever been inside a Detroit Diesel?
high-tech looking stuff that could've been designed in the 90s or later, but from 1935!

951and944S

Understood...., keep in mind, some PO eggheads sit at entire red light durations with their foot on the clutch...
I'd be more worried about the thrust bearing on the #3 crank journal taking pressure outside it's design limits than I would about a clutch fork.
I ran the Stg 2 Spec with carbon/kevlar disc on a 325 RWHP 944T for 3 years with -0- issues. Street and track use.
Lindsey can have Spec back cut the pressure plate and take another lb or two off.

Broussard...., normally doable, we have a few racing friends out that way (50 minutes from here) that we could arrange a meet up with for a Bar and Grill supper or whatever.
Thing is, my son is in Chicago for work this week, pulling out with trailer right when he gets back to S. Carolina to pick up a 968 another buddy just bought, then he's off to San Antonio for Seaworld and to drop a 104mm block to another racer friend and RL'er for me.

I can call the Whiskey Bay Region guys and see if they have a social dinner/bar night or something on the calendar if you wanna meet up with some PCar guys....?

If you're still there after mid-month, I'll give you a shout to see if we can make something happen.

T

951and944S

Same stuff, only bigger....

I had a buddy that was a diesel mechanic, always used to go on and on about diesels.

I did a wet sleeve Cummins overhaul in frame in a White Road Boss, fired up 1st crank and 2 x Mack dry sleeve overhauls for a buddy with a dirt service.

That was my take......same ****, only bigger.

T

Tom M'Guinn

I've tried spec, feramic and the KEP1/cup combo, and hands down the KEP1/cup combo creates the most street friendly car. The spec was a nightmare; the feramic was pretty darn good but still would shudder a little if you don't slip it etc.; and the KEP1/cup is smooth as stock and hold all the power I can make. I'm probably a broken record on these clutch threads, but I don't think anyone would pick anything else (for the street anyway) if they were able to compare them all. If you are at 400 ft lbs at the crank, one other option that "might" work is to use a cup disk (for factory smooth engagement) and couple it with a modified sachs pressure plate. Places like South Bend clutches can modify the fulcrum point to add more clamp force, which ends up being about half way between a stock pp and the KEP1. The stock clutch/pp is good for nearly 350 at the wheels, at least on a dynojet, so depending on how much torque you really have, a modified sachs pp is probably enough. It would put less stress on the fork (and firewall I imagine) than the KEP1, but more than the stock pp. That said, I've been running the KEP1 for 30k miles without fork or other issues, though I am careful not to sit on the clutch at stop lights etc. If you add strength to the fork to boot, I think the fork is fairly far down the list of things that are likely to break at 400+ ft lbs of torque.

944crazy

I have this same dilemma at the moment.

I have already gotten the TTV 60-2 flywheel....it's looks great and TTV's service was excellent.

While I'm in there I might as well upgrade the clutch. At the moment I'm leaning towards either Kep Stage 1 or Stage Lite, with a cup/sport clutch disc. The KEP PP are cheapest direct from KEP, and you can get cheap cup/sport discs off ebay. The only thing I'm worried about is clutch fork life with the extra clamp load. Apparently the KEP Lite is rated to around 420lb/ft...which is enough for my goals, and I assume it has a lighter clamp load than the Stage 1, so it should be ok for the clutch fork in the long run.

I was also considering a Spec stage 2 clutch...but people have such mixed experiences with them that I don't really want to risk it...not with how much effort is involved in a clutch job.

Thom

I have been running a KEP2/Cup set up for 60K miles with no issues whatsoever. Yes, perhaps the springs on the clutch disc are softening a bit, but this is probably due to the additional torque of the 3L engine.