Flywheel-Resurface or replace

[rlane]

I am performing a "pre-emptive " clutch replacement on my '78 SC while I am rebuilding the engine. The clutch was still within spec but down to the lower limits. I see no scarring or obvious hot spots on the flywheel.
Questions?
Should I resurface the flywheel, if so is this something that a local shop can do?
Any reason to replace?
Thanks

[tsuter]

Yes always resurface on a clutch replacement and no not a new one unless it cannot be resurfaced and yes replace all the nine bolts with new ones....

[rlane]

any reason not to use a good local (non-Porsche) machine shop

[Zeke]

Hey Richard, how's it going? (Richard helped me get my car)

I think resurfacing of both the PP and flywheel is a good idea when replacing the disc. I just wouldn't take them to any local machine shop that does everything. I like shops that specilaize in the thing you are refurbishing.

We have such a place here in LB called Friction Materials. They do nothing but brakes and clutches. If you go in tell them you want such and such finish on your work, they know what you are talking about. As far as what that finish that is on our cars, I don't yet know. Hopefully this thread will provide that info.

And, places that specialize in our engines seem to be a good choice too, even though that violates my theory about doing "everything."

Take care.

[rlane]

Thanks Zeke.
Would you have contact info for Friction Materials?
Anybody know what resurfaced fish to ask for (see Zekes' note)
What is the approximate cost?

[randywebb]

Only on the older cars do the flywheel bolts need to be replaced. P AG put out a TSB on this. We tracked it down in an old post on this bbs. Your '78 should be ok, but check the year on the old thread to be sure.

It will not hurt to replace them, of course - except a bit in the wallet.

[rlane]

Randy, if it the 90 ft-lbs vs 110 ft-lbs that they are torqued to...that did start in 1978 right ?

[randywebb]

not sure - check the tech spec book

IIRC, the changes all relate to the move to a different # of bolts/holes

BUT this is too important to rely on anyone's recollections...

[tsuter]

Yeah that's right.... don't spend $15.00 and replace those nine torqued bolts.

Go with the pundits, it'll be OK to reuse and you'll save $15.00......... and if it isn't OK and one comes loose ....well........no big deal right..... ?????

[Grady Clay]

Richard,

As with everything in your rebuild, all new parts are better. The “art” is not just throwing money at the project but using careful measurement and judgment.

There are clear dimensional specs for the flywheel. If you stay within the Factory numbers you should be just fine with a new disc and PP. The difficulty with a 915 and later is you can’t shim the clutch linkage to compensate for wear and machining the flywheel as you can with earlier (2.0 & 2.2) clutches.

I recommend you maintain a consistent attitude throughout your project. If you are building a like-new engine then certainly replace everything in the clutch. If you are doing a “maintenance overhaul” and money is an issue (when is it not) then machine the flywheel if it can remain in spec. If you run out of budget, spend the money inside the engine and reinstall the used clutch assembly. It is easy to replace later.

The clutch is just like the brakes – it is a system that is designed to wear in order to facilitate other automotive issues (like not locking-up the tires or over-stressing the drive train.)


The key to having things contracted to shops (like machining the flywheel) is being able to measure the original set-up and the result better than necessary. You get the best work when they know you have the specifications and will check their work.

With the PP, you will need to make the decision to use an OE type iron version or the aluminum version. Heavier (iron) is better for in-town street driving and lighter (aluminum) is better for sporting driving & DE events.

Make sure you use an appropriate spring-center clutch disc. For street use you absolutely don’t want a race type disc. You should summarily replace the pilot bearing in the center of the flywheel and the clutch release (TO) bearing. I agree with Randy, Porsche says you can reuse the flywheel bolts, I prefer new fasteners in this critical application.

Another “while you are there” is a new transmission input shaft seal, TO guide tube O-ring and “dam seal” modification. Just might save a nice new clutch disc. There are also some parts in the clutch linkage that should be looked at: The TO fork and attaching role pin, TO shaft bushings, the Ù-spring, the little bearings at the Ù-spring, seals and the clutch cable.

Make sure the clutch disc internal splines are perfectly free on the transmission input shaft splines and have a slight amount of moly grease.


Milt, these guys repair/resurface pressure plates?

There is a lot of this that has been discussed on the Forum. Please do a search and summarize for others. This in an important common issue.

Best,
Grady

[rlane]

I am trying to keep the budget intact but geez it is tough!!! Project began with discovery of a broken Dilavar head stud. Lots of hours later the head studs are all out, ARP studs going in. Henry Schmidt has the heads, John Dougherty is doing a 964 regrind on the cams (they had moderate pitting) and refurbishing the rockers. I just tore down all the CV's today. Now, this is all routine for you guys but the very idea of me doing this three years ago would have been laughable, I barely knew which end of a screwdriver to hold. Waynes books, the great information on here and folks you you all have made this a fun job!

I have already ordered new flywheel bolts, have the regular Sachs (spring loaded) kit with new PP etc, also have the new pilot bearing and most of the clutch linkage parts. Can you tell me what the "dam seal "modification is?

I did measure the flywheel and it appears to have plenty of thickness but will need the shop to check for runout. I am going to check with some of the local club racers and see who they trust locally to resurface a flywheel. Shops that specialize in our cars are rarer here than in California or Colorado. Anybody who knows of a good shop that is qualified to resurface these please drop me a note.

Of course after a satisfying day doing the CV joints I found myself looking at the 915 sitting in the corner and thing.."With Grady's threads I just might be able to tackle that bad synchro in 1st and 2nd""
Ah....the slippery slope is getting steep!!!!

[Grady Clay]

Randy,

Aah yes there is definitely some silliness here. You are to be congratulated, it is very satisfying to see Porsche people learn and take matters in their own hands. That is what I did almost 40 years ago.

Do a Pelican search on “dam seal.” It is an easy mod that prevents a leaking transmission input shaft seal from contaminating the clutch disc with oil. We developed this in ’72 then Porsche came out with the infamous 915 inside-out input shaft seal where you have to disassemble the entire transmission to replace this simple seal. The “dam seal” is applicable from pre-WWII VW and early 356 to current 997 and others along the way. No seal has infinite life, this just prevents the leak from causing farther damage.

Yes you can tackle some work on your 915. As Randy’s thread proves (Pelican rcecale) with Pelican support and more, many things are possible. ”Reconstructing Constant Velocity (CV) Joints”
To truly rebuild a 915 is a lot more work and I’m working on a set of instructions.

If done correctly, the slope isn’t so slippery. It’s like Colorado’s ego powder. You do just what you want and wow does it feel good.

Where in central KY are you – Lexington-Frankfort? I grew up in Louisville and have friends & relatives in many places. My Porsche owner dad (90) lives in the Falls City.

Best,
Grady

[rlane]

Grady, I am in a small town 30 miles East of Lexington but work in Falls City and Lexington (wasn't THAT a great beer!)

I am collecting a few thread links for future searchers:
Issues with incorrect resurfacing of flywheel: Clutch Replacement

Dam seal:Transmission input shaft oil seal on a 69 what's involved in replacing?


Good summary:Flywheel condition. How do I tell if it's okay?

Hope these help somebody

[randywebb]

dam seal - also:
Replacing 901 Tranny Shift Shaft Seal
go to last post (by Grady) with diagram