934 clutch and a bit of a prob.

[quattrorunner]

Installing my new clutch tonight when I realized my “custom” work was going to cause me some trouble. I had my 240mm flywheel cut up to make a little sleeve for my new aluminum flywheel bolt area. I was worried about the thickness of the sleeve but my machine guy was worried about it cracking if it was the thickness I asked for(1.2mm). So he cut it to 2.5mm but I’m not even sure it would have fit with the 1.2mm shim on there. My problem is that in the past I had installed one without any sleeve and the aluminum squashed under the torque of tightening the bolts.
So with the sleeve I have no contact with the flywheel. The flywheel bolts get in the way. I don’t want to buy a new flywheel the clears so I guess I’ll do some more machining of the aluminum surface area for clearance. I’ll take the parts to work and see how it all works out. Anyone have any other ideas?

[pkabush]

That’s a bummer. One thought would be to have the flywheel bolts turned down but, IDK if that would leave enough meat on the torx opening. I think I have a spare set of used f\w bolts. You’re welcome to them if you want to use em for testing.

[quattrorunner]

Thank you! Actually what I’ve done is milked the inside of the flywheel, the surface that sees the bolt faces down 2.5mm to make room. Dang this is getting esspensive

[pkabush]

Yah, these cars seem to find a way to break our bank accounts even when we do most of the work ourselves. Good luck.

[quattrorunner]

I ended up grinding the heads of the bolts down maybe a mm. Just in case. I was thinking about wear on the disk and worried about doing this again. Btw holy hell is it that I’m getting old or is it insane getting the trans and engine mated? Yes I’m getting old but gee wiz. I’m taking the disk off tomorrow to see if maybe the splines are not fitting.

[T77911S]

do you have the tool to center the disk.
that is a big help.
you don't need a fancy expensive one. I bought a plastic one.

[jwasbury]

Consider that the clutch disc itself is the issue. You say that is a new part in the assembly but you’ve used the flywheel before successfully?

I had a similar issue a few years back, was assembling my engine and trans, lightweight aluminum flywheel being reused and a brand new friction disc from clutchnet. I got everything assembled and pressure plate torqued successfully, but the trans would not mate with the engine. Turns out the clutchnet clutch spring bulges were larger than the disc it replaced and it was pushing the pressure plate out and making it impossible to mate the engine and trans. If I had successfully mated them and put the engine in the car, the damn clutch springs would have torn the crap out of the flywheel and pressure plate.

I reassembled with my old clutch plate (a Sachs racing 4 puck), and all was well. When I put the two discs together, the dimensional differences were pretty obvious. In my case (possibly yours too), the aluminum flywheel is thicker that a stock steel one (i needed to use longer flywheel bolts too, a 928 part number). I believe the clutchnet disc would have been fine with a stock flywheel but just wasn’t compatible with the aftermarket aluminum one. When I called clutchnet with the issue, the guy said he “got it” and they had a different suitable disc he would swap for me. Its still unopened and I haven’t checked because the 4 puck Sachs is still going fine in there today.

[quattrorunner]

jwasbury
That is very interesting.......My flywheel is new and the whole clutch is also new. The disk is supposedly a thinner unit to fit the 934/5 pressure plate but the thickness of the flywheel is a concern. The original is cut up for that shim I was talking about earlier and I don't have it to check now.
I also had to shorten pressure plate bolts last time I did a clutch job (seems like I've done a billion but is getting tougher each time instead of easier. Last time cause I didn't use the alignment tool I had to manhandle the throw out with the arm while also pushing the trans onto the engine but I doubt I can this time with stronger presureplate..
Well see, I'm getting the alignment tool later today I hope.

[jwasbury]

If this is your initial installation of the aluminum flywheel, I'd strongly encourage you to verify its thickness vs. the stock part. If, like mine, it is noticeably thicker, then I would further encourage you to carefully check thread engagement of flywheel bolts into the crankshaft. When I was reassembling this engine, I had bought new flywheel bolts (stock part number) and when I was comparing to the ones removed, I noted the new ones were materially shorter and many fewer threads would have engaged in the crankshaft. Conversely the correct bolts for the application (which turned out to be a 928 part number) would be too long when used with the stock flywheel, and would bottom out in the crankshaft. You definitely don't want to screw around in that area. If a flywheel bolt lets go when the engine is spinning you've got a big mess on your hands (of course you know this).

Originally Posted by quattrorunner

jwasbury
That is very interesting.......My flywheel is new and the whole clutch is also new. The disk is supposedly a thinner unit to fit the 934/5 pressure plate but the thickness of the flywheel is a concern. The original is cut up for that shim I was talking about earlier and I don't have it to check now.
I also had to shorten pressure plate bolts last time I did a clutch job (seems like I've done a billion but is getting tougher each time instead of easier. Last time cause I didn't use the alignment tool I had to manhandle the throw out with the arm while also pushing the trans onto the engine but I doubt I can this time with stronger presureplate..
Well see, I'm getting the alignment tool later today I hope.

[quattrorunner]

I don’t know how I’m going to get that disc centered enough to fit that clutch. I removed the disk to make sure it’d slide on and it was difficult all by itself. The tolerances are crazy close. I’ll order that centering tool but I doubt it’ll help.

[TurboKraft]

Hi,
+1 what Jacob said, and if you call tomorrow to remind me, we can measure a 930 flywheel to make sure yours has similar hub dimensions to an original one.
Flywheel bolt torque = 62ft.lb. and a drop or two of red threadlocker is recommended (chase and clean all threads first)
That pressure plate requires that disc, and we just installed 3 of them so I'm inclined to think yours is fine, too.
You will need a clutch alignment tool, and a plastic one is fine. If you need one asap and have a decent NAPA or similar auto parts store nearby, take in the disc and match the alignment tool. There's a Mitsu and a Ford tool that both fit.

[quattrorunner]

Great info as always thanks.

[quattrorunner]

I measured the flywheel center section at 12mm thick.

[jwasbury]

Some threads that may be of interest.

The 1st is from my own aluminum flywheel challenge. I ended up using p/n 928-102-151-01-M260 for flywheel bolts. They are 4-5mm longer than the stock 911 part number.

http://forums.pelicanparts.com/911-engine-rebuilding-forum/872422-flywheel-bolts-lightweight-aluminum-flywheel.html

http://forums.pelicanparts.com/911-engine-rebuilding-forum/623551-long-flywheel-bolts.html

[TurboKraft]

Originally Posted by quattrorunner

I measured the flywheel center section at 12mm thick.

-1989 steel flywheel hub = 8.35mm thick
uses standard 911/930 flywheel bolts

[quattrorunner]

I’ll look into some new bolts thanks guys.

[quattrorunner]

Bolts were nearly bottoming in the crank. All thread locked. Maybe a couple more millimeters.
And hank goodness for that alignment tool. It came together great.