Clutch conversion question, Pull clutch conversion Options

[DeeEmm]

Hi all.

I have a clutch compatibility question.

First here's the parts I have

I have a 914-4 that I purchased without engine and Box. Because...
I already had a 915 box from a 911 SC and a 2.7 Type 4 that has a KEP flywheel with a 911 pull style clutch and ring gear from another project.

My idea was to convert the 915 to work in the 914. But after owning the car for a few years and making no progress, I've changed tact and decided to buy a stock 914 box as one has come up for sale locally. (a rare occurrence here in Australia) Fitting the engine and a stock 914 box is definitely a shorter pathway to getting it back on the road.

So my question is this...

Can I convert the 914 box to work with the pull clutch?

I know that I can change the flywheel to a regular flywheel, but the engine was built and balanced with the KEP clutch and plate, so I would really like to avoid having to tear it down again to get it rebalanced.

I've seen several references implying the box can be converted to a pull style, but I cannot find any hard info on it or anyone who's done it.

The other thought that I had was using a push style pressure plate but still retaining the KEP flywheel and ring gear. But, I'm not even sure if that is possible. Does such a configuration even exist? It would be super convenient if it's just a case of mixing and matching components, but I'm rarely that fortunate.

I do have machining capability as in the sparse info I could find on converting the 914 box to a pull clutch it mentioned machining the release arm pivot? But in the absence of any additional info, I have no idea what that actually entails.

So thought I'd reach out to the brains trust and see if anyone has any ideas / experience on this.

(IMG:http://www.914world.com/bbs2/uploads_offsite/vdubber.com-28216-1781580132.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/vdubber.com-28216-1781580133.2.jpg)

Thanks in advance

[targa72e]

Other can chime in with more details.
Basics I know. The pivot ball is in a different location. Generally recommended to use a insert into the transmission housing and then thread into insert as the Pivot ball can pull out. You need the clutch pressure plate, Clutch fork and throw out bearing from a 2.2 911, all are expensive. Not sure what you use for a clutch cable, might be custom.

john

[DeeEmm]

Thanks John, that's been a fair bit of help and set me on the right path. I managed to find a bunch of info online based on the info you gave and managed to get an understanding of how it works and the differences between the push / pull setups.

Found an article that explained the difference in pivots and pivot locations and the arms

Found a used release fork on ebay for a very reasonable sum

Ordered a new ball stud pivot

Looking at photos I'm pretty sure the release bearing that I already have is the right one, but will need to wait until I get out in the workshop and have time to dig the engine out to be 100% sure. Looking at photos I think it would be possible to make it work if it wasn't by modifying the arm. Worst case I need to get a new bearing

So I think I'm now mostly set. Of course this will all change when I actually offer the parts up. But that's half the fun, isnt it? lol

Still very interested to hear if anyone has done this mod and if there's any pitfalls I should be aware of

[stownsen914]

I've done the mod to a 914 trans. If you're lucky to find a 70-71 911 trans, it has the mod. If you're doing it to an earlier 901 or to a 914 trans, you need to have the case machined for an insert for the pivot (magnesium isn't strong enough by itself to resist the pivot bolt pulling out). As mentioned above, the pivot is in a different place, so the shop needs to know where to put it. I happened to have a 70-71 trans case for the shop to copy. Then it's just getting the right parts. For a 911 engine, a standard 72-77 flywheel and clutch bolts up (with a 70-71 911 TO bearing). For a VW motor, I guess you'd need a special flywheel for the crank hub pattern.

[Montreal914]

1970 and up 911 pull clutch uses a 225mm clutch disk, whereas the push style early 911 and 914 is 215mm, but you probably know that.

For a 911 engine, a standard 72-77 flywheel and clutch bolts up (with a 70-71 911 TO bearing).

Small caveat, the 72-77 911 clutch that is normally mated to a 915 is stiffer than the 70-71 911 clucth that is mated to the 911-901. Many 70-71 911-901 box got their pivot bolt pulled out of the case because they were mated to the stiffer 72 and later clutch.

P/N for the 70-71 911 pressure plate is 911 116 001 05 and Sachs P/N is 3082 018 431. You might want to check what PP you have in there. (IMG:style_emoticons/default/smile.gif)

[DeeEmm]

1970 and up 911 pull clutch uses a 225mm clutch disk, whereas the push style early 911 and 914 is 215mm, but you probably know that.

For a 911 engine, a standard 72-77 flywheel and clutch bolts up (with a 70-71 911 TO bearing).

Small caveat, the 72-77 911 clutch that is normally mated to a 915 is stiffer than the 70-71 911 clucth that is mated to the 911-901. Many 70-71 911-901 box got their pivot bolt pulled out of the case because they were mated to the stiffer 72 and later clutch.

P/N for the 70-71 911 pressure plate is 911 116 001 05 and Sachs P/N is 3082 018 431. You might want to check what PP you have in there. (IMG:style_emoticons/default/smile.gif)

Thanks Montreal914. That's a pertinent bit of info.

I really need to dig it out to take check of what's there already. I built the engine over 20 years ago, so cannot remember exactly what the clutch specs were, but the engine spec was turbocharged 2.7 for my Karmann Ghia with an output of 300-350hp, and so I can recall going down the pathway of using the 911 clutch as it was a better option than using a VW clutch at the time, so I have a feeling that it's going to be the stiffer version. But I cannot say for sure.

It's most likely going to remain normally aspirated when i fit it into the 914, as I'm not trying to break any records now. lol.

I did manage to find a photo of the pressure plate and friction disc, but no identifying details other than what it looks like

(IMG:http://www.914world.com/bbs2/uploads_offsite/vdubber.com-28216-1781653158.1.JPG)


I have a machine shop so can machine the case for an insert. When I get all of the parts here. I'll take a look and see if there's any way to strengthen it. I'm wondering if it's possible to spot face the inside of the diff housing and make a sex bolt / nut to hold the pivot rather than rely on a thread-sert or maybe add a plate with some additional fixings to spread the load. There's got to be a solution in there somewhere. Machine time is essentially free for me, so if I can manufacture a solution it's preferable to throwing more money at this thing lol

[stownsen914]

It's a good point about the 70-71 clutch not being as stiff as a 72-on one. I used a 72-on aluminum sport clutch in mine. On advice from others, I red loctited the pivot in the case when installing. It didn't pull out, but it did break eventually lol, so there's that. Did a trackside repair with a regular M8 bolt and it held until the next time the trans was out for other maintenance. Not sure of the metallurgy on the factory pivot bolt, but I imagine it could be improved.

[Montreal914]

There is someone on early S registry that makes nice pivot bolt replacement.

I will try to provide information later today. I bought one for my 911-901 that I plan on converting for 914 use.

[DeeEmm]

An aluminium clutch is sage advice, as the one I have is heavy AF. I note that the aluminium versions are 1.7kg lighter. That's a fair difference.

It was one of the disappointing parts of the engine build - spent a lot of money lightning and balancing everything only to use the worlds heaviest clutch setup. Coming from a 'performance' car I'd naturally assumed it would be lighter lol. Also never really liked the release bearing setup, just more weight permanently attached to the crank. Had I been aware of the alu pressure plates at the time I'd have definitely gone that way. Maybe if I swap the cam over I might look at one. (it has a turbo cam)


This is the pivot bolt I purchased.

(IMG:http://www.914world.com/bbs2/uploads_offsite/www.mhteile.com-28216-1781751404.1.jpg)

https://www.mhteile.com/en/p/3105-clutch-re...77211-911310020


I've been down the rabbit hole a bit with clutches and pressure plates. Don't know how accurate this info is, as some of it was AI assisted. Seems that to increase the clutch size when the 2.2 was introduced, but still manage to squeeze it all in the 901 bell housing, Porsche removed the ring gear and relocated it to the front of the pressure plate so that they could squeeze the 225mm clutch in. Which makes a lot of sense and explains the kooky ring gear setup. Needs must etc.

Gemini suggested that for two years 70-71 there was a push style release clutch pressure plate that had the seperate ring gear. After that, they moved to the 915 box and it changed to the pull release. but I cannot verify this at all as all of the two part pressure plates I can find are pull release and the ones listed for the 2.2 70-71 do not specify push or pull. So I'm thinking it might be an AI hallucination.

[stownsen914]

70-71 was definitely the pull style clutch release. The pressure plate is dimensionally the same later 915 units - the 70-71 version just had a lighter diaphragm spring.

I thought I read the 70-71 version had been superseded and wasn't available anymore? (So you'd use the 72-on version, which bolts up.) For sure the 70-71 aluminum S version is NLA. They were silly light.

From the pic, it looks like you have an aluminum pressure plate?

[Dave_Darling]

I recall that @ClayPerrine researched this pretty well at one point?

--DD

[DeeEmm]

stownsen914 no it's definitely steel / cast steel - managed to dig the engine out this arvo and its showing its age a little lol.

(IMG:http://www.914world.com/bbs2/uploads_offsite/vdubber.com-28216-1781762853.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/vdubber.com-28216-1781762854.2.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/vdubber.com-28216-1781762855.3.jpg)


Numbers on the pressure plate are 3032.055.099 / TYP GMFZ 225

I found a post on Pelican parts that described the difference between GMFZ and GMZ, whilst not conclusive it said that the GMFZ was the higher pressure version.

https://forums.pelicanparts.com/porsche-911...ate-please.html

It also had another interesting tidbit of info - the 915 has the omega spring, which assists the clutch action, whereas the earlier boxes didn't. A another possible change to support the heavier clutch.

So my clutch not only operates the wrong way, it's also likely too stiff, no wonder the pivots pull out. (IMG:style_emoticons/default/blink.gif)

[DeeEmm]

Ok so the first part of the puzzle has arrived...

(IMG:http://www.914world.com/bbs2/uploads_offsite/vdubber.com-28216-1782433292.1.jpg)

[Montreal914]

What Google says on that pressure plate is that it was on the 924 turbo. (IMG:style_emoticons/default/confused24.gif)

Question is, what the spring force? Does it compare to the 70-71 PP or is it more like the stiffer PP used with the 915. Again, beware of the weak pivot point.

I bought my pivot bolt from Jim Tidwell on Early S Registry.

Here is the link:

https://www.early911sregistry.org/forums/sh...802#post1082802

[DeeEmm]

Thanks for the link Montreal914.

Will check out the one I've bought when it gets here. I'm hoping it's also heat treated, but if not I'll grab one of those. Nothing worse than having to do a complete teardown for a $30 part

Weird thing with Google, it's also telling me the wrong thing - that it's an aluminium 911 pressure plate, go figure lol.

And they say AI is going to take over the world lol

[zig-n-zag]

I kept the clutch assembly from a 1970 911 I had separated some 25 years

ago. In the box it was stored was a flywheel, clutch disc, the pressure

plate with the ring gear and the throw out bearing.

Pressure plate is Fichtel & Sachs AG Typ MFZ 225. It is aluminum. Part #

303 201 5399 -b1. The throw out bearing has ears laying flat. The clutch

disc also differs from yours as there are no springs in the center on the one

I have. Sorry, I lack the skills to post pics, however you can PM me your

contact And I’ll send you the pics. I’m in Honolulu, Hawaii.

[DeeEmm]

PM me your contact And I’ll send you the pics. I’m in Honolulu, Hawaii.

Thanks Zig-n-zag

Message sent.

[Montreal914]

Pressure plate is Fichtel & Sachs AG Typ MFZ 225. It is aluminum. Part # 303 201 5399 -b1.

Do you know for sure this was the clutch assembly that came on the car out of the factory in 1970?
This P/N shows the PP as being for a 915. (IMG:style_emoticons/default/confused24.gif)

[zig-n-zag]

The 225mm pull type clutch disc found in the 1970-1971 will not fit on the

1972 and up 915 transmissions because Porsche changed the input shaft

splines, from 24 to 20. The aluminum MFZ 225 does not use the 225mm

spring-centered clutch disc part #915 116 011 22. The pull type clutch

disc for 1970-1971 Part #911 116 011 07 has fine splines, and it has a no

spring center. And the 1970-1971 911 release bearing Part #911 116 081

02 has the 2 ears on it, unlike the 1972-1986 release bearing which has

no ears and different Part #915 116 082 80.

[Montreal914]

All in agreement.

The big question is what is the pressure plate? All of these 70 through 86 pull-type PP can physically be mounted and fit on a 70-71 gearbox (with proper disk and release bearing) but they differ in spring force weather they are cast iron or aluminum versions.

To use a 70-71 911 box and avoid pulling or breaking the pivot point, you want the low spring force PP which was officially used with the 2.2 engine in 70-71 and has P/N 911 116 001 05 or Sachs P/N 3082 018 431.

That being said, I think there may also be an aluminum version for 70-71 but I don't have the P/N. Maybe it was used on the 70-71 911S?

I found this info searching various years of PET and suppliers.
When doing search with AI, it is completely off and provides a bunch of BS including saying it uses a push type clutch. I wouldn't trust it. (IMG:style_emoticons/default/icon8.gif)