Washers...

[Mitch Leland]

Howdy,

I'm dropping my engine for a clutch job. Two questions:

1. Why isn't there S.S. flat washers on the exhaust system connecting hardware?

2. Regarding the allen hex head bolts at the rear CV hubs. I see in the parts book that it appears that the SC had a two hole plate under the allens. But it appears, and this is my question, is there suppose to be flat or lock washers under the allens on the 930 and my Turbo Look cars?

When I removed the allen bolts there was nothing under the heads.

Thanks as always,

[The Turk]

I used ARP stainless steel studs with copper lock nuts where the headers bolt to the heads.
Porsche recommends Schnorr Washers P/N: 999-523-103-01 between the Allen bolts and the plate with the two holes in it, somebody must have left the Schnorr washers out when they had your apart, the plate helps distribute the load evenly, I’d use both.

[Mitch Leland]

Thanks Gary, I'll go back with all new copper stop nuts, but I think I'll use S.S. flat washers under them. I hate torquing down nuts with having washers.

However I don't see the Plate for the M491. I see P/N 911 332 191 00 which might be for the non M491? The 930 and TL have a 10MMX60 allen head, the regular SC has a 8MMX50 allen head. The parts book refers to the allen as a "pan head"?

I'm sure our host can clear this up when I get ready to order the parts. Thanks again...

[Wil Ferch]

There is an incredibly long and detailed thread on CV joints and connecting hardware. Guru Grady Clay contributed as well as fastener expert Jim Sims (sp ?). I'll post if I can find , otherwise do the proverbial search. No simple answers here on this topic and many places to go wrong. Too many combinations of pieces that will fit but may be wrong
- Wil

EDIT: here it is. Get a big cup of coffee and prepare to read and learn first---> Reconstructing Constant Velocity (CV) Joints

[Gunter]

I found that it is more important to have new lock washers under the Allen heads than using the half-moon plate.
Either way, make sure that the new Allen bolts don't protrude too far and prevent the axle from turning.
Use a cross pattern when torquing; pre-torque first, then do the final torque.
I don't use the plate, just bolts and washers.
No gaskets for me, just metal on metal.

[Mitch Leland]

Thanks to all for the info. Wil's direction to the CV Tech Thread was very informative.

It appears from the parts manual and the tech thread that the "84" TL didn't use a gasket and didn't use the arc plate, just washers.

[Tut]

I have 10mm Schnoor washers if you need them.

[Mitch Leland]

Thanks Tut, yes I'm going to need the washers. I'm sure our host stocks them. Thanks so much for your offer.

What are Schnorr washers. Do they have a slight chamfer on one side. If so then do the alan hex bolts have a chamfer on the underside of the head?

I have similar bolts and washers on the landing gear of my airplane that are under high loads.

[Wil Ferch]

Schnorr washers are variations of serrated Belleville washers. In profile, however, Schnorr have the "peaks" angled over more to one side..resisting unwinding movement better than if the peaks are not angled over..and simply straight up. Somewhere in that long thread I mentioned..Grady Clay has a nice diagram. I also believe that Schnorr has the ridges go out offset-radially, and not purely radially like Belleville.

Here it is. Page 8 of that thread---> Reconstructing Constant Velocity (CV) Joints

BTW..I'm torn about using Schnorr washers without the moonplates. Schnorr washers, like Belleville, compress like a spring and the surface they act on has to be hard. If you don't use the "dogbone" moonplates, then the Schnorr dig-into the softer CV joint stamped metal..rendering the Schnorr almost useless IMHO.

- Wil

[Mitch Leland]

Wil, thanks for the follow up... I agree I probably will use the plates for the very reason you mentioned. In my case I have the 930 machined spacers on the CV joints. But still feel the same way...

Do good...

[Gunter]

Lots of pros and cons about types of washers.
As for the intent of lock washers: IMHO they are meant to "dig in" meaning that the teeth cannot bite if the metal surface is harder than the washer itself.
Schnorr, and other types, have a certain hardness to them by design.
I found that it is more important to torque crosswise (with pre-torque) on the CV's and I leave out the gaskets which I feel are responsible for the Allen bolts coming loose.
I use Schnorr type lock washers.
Moonplate yes or no? Whatever feels good; I have no opinion either way but I don't use them.
Some parts of the engine have high vibration, yet, Porsche doesn't use any washers like on the exhaust studs and other areas.
Go figure.

[Mitch Leland]

Thanks Gunter, I appreciate the information. It does seem like a disparity that there are no washers on any of the exhaust system including the headers at the cylinders. Unless I hear something different I'm going back with washers on the exhaust.

I think for now I'll also go back with the plates and washers for the connection at the inside CV joints. You mentioned not using the gaskets at the CV connection, in my case when I separated the spacer from the CV flange there were neoprene gaskets, but they appeared to have been down in the hub and not in place. I'll know more once I get the hub and spacer cleaned up.