clutch/flywheel choice

[r lane]

A 3.0 aircooled track car. Presently has a heavy duty pressure plate, puck type disc and a Patrick flyweel. Considered for some time a Tilton type clutch. A friend of mine who runs one on his car, 5'' version, states is one of the best things you can do for the engine. The rotating mass both up and down. It appears to be a considerable amount of work. Not an inexpensive clutch and flywheel kit and sourcing a pedal cluster has come up zero. Am looking at an earlier pedal cluster to see if it lends itself to being modified to handle the job. I think so with having to buy a few OE type links, or possibly reinvent the linkage part. Any experience and pros and cons to this subject would be appreciated. Bob

[Henry Schmidt]

The last two race engines we built [2.0 and 3.4] used 5", dual disc clutches. One from JB Racing and one from Patrick. Both seem like very high quality.
One of our guys ran an Aasco light weight clutch and flywheel package with mixed reviews.

[stownsen914]

The benefits of a small diameter racing clutch are clear enough for a racing only application. A couple considerations:
It takes a little practice to let the clutch out and get the car rolling with one of these. First time I tried one, I think I stalled the engine 6 times in a row before I got going lol. Not hard once you figure it out though, and fine for racing only use.
They don't tolerate slippage very well. If you slip them a lot to get the car moving (see above note), they overheat and/or wear out quickly. For example, you may not want to drive onto a trailer with one of these. Not an issue if you don't abuse them though.

As for pedal box mods, if you mean to convert to hydraulic clutch actuation (not a bad idea due to higher pedal effort), yes it's possible. I have such a setup with my 911 racecar. I'm just using an RSR clutch, but it's the same idea. I think my setup uses a 944 or late 911 master and a matching slave cylinder on the trans end. It's a modified 911 pedal cluster.

If you are thinking to use a cable, I understand that can be done too with a 5.5" Tilton on a 915. Whichever way you choose, one thing to keep in mind is I think the Tilton is a push clutch (opposite the regular 915 clutch), so some fabrication might be needed. It looks like the JB Racing kit includes a special bobbin for the release bearing, so they must have a recommended way to do it.

[r lane]

Originally Posted by Henry Schmidt

The last two race engines we built [2.0 and 3.4] used 5", dual disc clutches. One from JB Racing and one from Patrick. Both seem like very high quality.
One of our guys ran an Aasco light weight clutch and flywheel package with mixed reviews.

Morning Henry, I think like much of a race car, you have to acclimate to a new system. Did they share their likes and dislikes. Thanks, Bob

[r lane]

Originally Posted by stownsen914

The benefits of a small diameter racing clutch are clear enough for a racing only application. A couple considerations:
It takes a little practice to let the clutch out and get the car rolling with one of these. First time I tried one, I think I stalled the engine 6 times in a row before I got going lol. Not hard once you figure it out though, and fine for racing only use.
They don't tolerate slippage very well. If you slip them a lot to get the car moving (see above note), they overheat and/or wear out quickly. For example, you may not want to drive onto a trailer with one of these. Not an issue if you don't abuse them though.

As for pedal box mods, if you mean to convert to hydraulic clutch actuation (not a bad idea due to higher pedal effort), yes it's possible. I have such a setup with my 911 racecar. I'm just using an RSR clutch, but it's the same idea. I think my setup uses a 944 or late 911 master and a matching slave cylinder on the trans end. It's a modified 911 pedal cluster.

If you are thinking to use a cable, I understand that can be done too with a 5.5" Tilton on a 915. Whichever way you choose, one thing to keep in mind is I think the Tilton is a push clutch (opposite the regular 915 clutch), so some fabrication might be needed. It looks like the JB Racing kit includes a special bobbin for the release bearing, so they must have a recommended way to do it.

Stownsen, don't think I was aware there was a cable option for those clutches. The hydraulic system is critical I hear to the hose size. Do you feel that clutch is a significant benefit. I am sure there is engineering calculations that would show power transfer. In real time, I assume the engine spinup is faster, car is faster. Thanks for your info. Bob

[dannobee]

We used Tilton's almost exclusively in nascar. Always with the hydraulic slave that goes around the trans input tube. Works great. AFAIK, all are triples and dual discs are push style.

We've even driven them in parades, but as townsen said, it does require some finesse and practice. Getting the car up on the trailer without slipping is best accomplished with a running start and nerves of steel until you get used to it. If you think idling up to the ramps, then stopping and getting your bearings is the only way, you'll quickly burn it up. Running start and use momentum to carry you onto the trailer.

They do make clutch plates for street use if you choose to go that route, and any replacement parts are usually far cheaper than the "regular" Porsche/Sachs clutch parts. They can even be rebuilt in-house if you have the requisite tools.

If you happen to be using a G50, the input shaft size and spline count is 1"-23. Common as dirt in racing circles and used by many other manufacturers. That'll save you money and not limit your choices to Tilton, FWIW.

[Walt Fricke]

These (the Tiltons anyway) are a push clutch. That makes using a hydraulic TOB system desirable. However, you can also use a clutch cable. Obtain an early 912 external release arm. Mount it so it points at an angle forward and and a bit to the right. Route a suitable cable end (the threaded kind) through the protrusion on the bottom of the tranny case. If the protrusion isn't drilled out, drill it. It works. Less expensive all around than a hydraulic system, though requires more leg strength. WEVO sells (or sold) a hydraulic system. WEVO recommended a larger hydraulic line size than one might expect for their setup.

[stownsen914]

r lane - hadn't seen your question above about measurable benefits of a small clutch. I haven't personally done a back to back with and without one. I can say that my car that uses the 7.25" clutch with a smaller flywheel revs veerrry freely (in neutral and when in gear), moreso than 911 powered cars I've driven that have Sachs aluminum clutch + RSR flywheel setups.

I found a couple pics of a custom cable setup for a Tilton clutch on a 915 that another Pelican sent me, for your perusal.

[stownsen914]

Also have a copy of the instruction manual for Wevo's 915 setup, showing a diagram of the parts involved. And a pic of the JB Racing 915 setup showing the special release bearing / bobbin. If I recall correctly, they leave it to the purchaser to figure out the release mechanism (hydraulic or cable) using the 915 TO release arm.

Hmm, having trouble attaching the Wevo manual for some reason.

[Henry Schmidt]

Originally Posted by r lane

Morning Henry, I think like much of a race car, you have to acclimate to a new system. Did they share their likes and dislikes. Thanks, Bob

We've used the JBR, Patrick and Tilton 5.5" and 7" dual disc clutches on everything from 2.0 to 3.8 liter race engines. Even my Riley DP car with 3.9 flat six used a factory version of the triple disc Tilton. (see picture) The people we have using the 5.5" clutches are happy with peddle response, disc engagement and track life.
One had an issue with an Aasco flywheel cracking the first time out but we all know, "Race parts have no warranty".

Clutch and flywheel package from JBR on a 914-6 historic GT.



Clutch package for my Riley.




Porsche Motorsport clutch/flywheel package

[r lane]

Originally Posted by Walt Fricke

These (the Tiltons anyway) are a push clutch. That makes using a hydraulic TOB system desirable. However, you can also use a clutch cable. Obtain an early 912 external release arm. Mount it so it points at an angle forward and and a bit to the right. Route a suitable cable end (the threaded kind) through the protrusion on the bottom of the tranny case. If the protrusion isn't drilled out, drill it. It works. Less expensive all around than a hydraulic system, though requires more leg strength. WEVO sells (or sold) a hydraulic system. WEVO recommended a larger hydraulic line size than one might expect for their setup.

I have been told, dash 4 not 3 as 3 creates a fluid resistance and doesn't allow the TOB to release quickly enough as you lift off the clutch pedal, causing the clutch to slip. Thanks for the info on the cable setup all. As one looks for ways to make the car faster, besides improving ones driving ability, the efforts become more expensive, and seem to deliver smaller benefits. With the lighter clutch, the lighter rotating mass frees up the crank, but it still has the same weight of the car to tug down the track. So it is just one part of accumulative efforts, and the person willing to continually step up, usually is out front. Speaking of, I am in the market for light weight hood and doors. Will post in Classified Parts.

[Sboxin]

Originally Posted by r lane

A 3.0 aircooled track car. Presently has a heavy duty pressure plate, puck type disc and a Patrick flyweel. Considered for some time a Tilton type clutch. A friend of mine who runs one on his car, 5'' version, states is one of the best things you can do for the engine. The rotating mass both up and down. It appears to be a considerable amount of work. Not an inexpensive clutch and flywheel kit and sourcing a pedal cluster has come up zero. Am looking at an earlier pedal cluster to see if it lends itself to being modified to handle the job. I think so with having to buy a few OE type links, or possibly reinvent the linkage part. Any experience and pros and cons to this subject would be appreciated. Bob

Bob,

I really didn't want to get into this discussion - but, we switched to a Kennedy Engineering clutch on the advice of CMS who does our 915 race transmission - we broke a Sachs pressure plate (10 years and 100 hours racing - should have replaced sooner) with our 3.8L 964 race engine. Our engine builder here in Phoenix (Don Jackson Enterprise) called and talked to KEP and installed the suggested KEP clutch which mates up to our Patrick flywheel. My son (the driver) said the clutch works great! KEP is in Lancaster, CA.

All the Best on your project,
Regards,
Roy T

[winders]

Originally Posted by r lane

I have been told, dash 4 not 3 as 3 creates a fluid resistance and doesn't allow the TOB to release quickly enough as you lift off the clutch pedal, causing the clutch to slip.

If you are using a Tilton MC, they are all -3..so does using -4 lines with a -3 MC really make a difference?

[Walt Fricke]

Hayden at WEVO is the source of the "use -4, not -3" or the like advice. I think I read that in a WEVO manual or catalog back when.