Fastener clarifications

[notmytarga]

I'm gathering all the supplies and readying my parts for assembly and have come up with some gaps in my inventory that aren't answered by searches in Wayne's book and in the forums.

The rebuild book on page 74 refers to "oblong-shaped nuts" for attaching the chain housing. The host (Pelican) site lists "oval-shaped locking nuts" only as part of the Hardware Superkit. The hardware listed in the online catolog does include "oval self-locking washers" and also "spring washers"

I ran all my hardware through a cleaning process that might as well have included terminal sterilization and didn't want to spring for the hardware kit which would have given me barrel nuts and such that I wouldn't need. I did plan on reusing the M8 nuts for the cam/head connection and others. I did plan to get new M6 and M8 Nylocks and aluminum washers. (the washers are holding up my order giving me more time to worry about all this.

Also - I can't find circlips - that is piston wrist pin circlips - thought the gasket kit might have them - nope. Pelican catalog searches come up empty. My machinist will send some. The circlips are not mentioned in the Must-replace parts pages 71-75, but I've read that they are - somewhere. And of course one flew away from me. The comprehensive part layout picture on Page 140 doesn't show any.

What are 'oblong' nuts and are they really washers? The nuts that came off this 1975 engine didn't look 'oblong' - what do I need?
Do all the M8 standard nuts really need to be replaced?

[euro911sc]

Those are all metal lock nuts. The harware kit calls them oval and they are to an extent. On my '82 I had regular nuts with spring washers... though the heads had been off before so I suspect the POS-PO just used what was on hand... along with his tube of RTV... blech!

the wrist pin circlips are not standard in gasket kits. for that matter they are not traditional circlips either... just bits of steel wire. See for a blury pic:

http://forums.pelicanparts.com/showthread.php?t=413564

enjoy!

Michael

[304065]

The exact name for those nuts is "prevailing torque lock nuts." Many recommend their use, but there are two problems with them:

1) They can deform the threads, requiring replacement of the stud if you for whatever reason have to disassemble and reassemble during the rebuild process (if, for example, you forgot the timing chains when you assemble the oil pump, oil pump drive shaft and intermediate shaft, which happens more frequently than many would like to admit); and

2) You don't know what torque value is required to achieve correct preload in the stud. When you use a normal M8x1.25 nut with a lock tab, you put it on and torque it to the book value, bend up the tabs and you're done. With a prevailing torque nut, you are actually deforming the triangular threads around the stud, and you achieve a much higher torque value. So when do you stop, how do you know you aren't stretching the stud beyond its elastic limit? Well, you know when the stud shears off.

Anyway, I have a whole bunch of them and I haven't used any in my engine.

The reason you replace the hardware is because it is cheap, because threads deform when preload is achieved and you don't know the history, and because the flats of the nuts are often deformed by prior assembly. If you are doing concours you MUST re-use all your old hardware and you get to be an expert in the correct headmarks and finish. Which I assume isn't your problem.

A lot of the hardware out there is made in Taiwan, the headmark tells the story. Even the Wuerth "German" hardware has a headmark that says it comes from somewhere else. So buyer beware. Search this forum for "headmark" for more than you ever wanted to know. Certainly it's not an aerospace application so chain of custody from the producer to the retailer isn't that important (it sure as hell is for aircraft bolts) but you don't want to use nuts made from zinc plated matzoh meal.

If you are not doing concours, replace everything, it will look good and give you peace of mind.

[notmytarga]

I now know a lot more. Thanks John. It seems like those prevailing torque nuts would do damage to the stud threads.

All the M8 nuts that came off my engine(s) were either nylock or they seemed pretty normal. Do those PT nuts look essentially the same as a non locking M8 nut?

[304065]

No, they have an almost conical side and a flat side and you can clearly see that the threads are deformed in a triangular or oval shape.

I don't have much use for Nylocks except for the valve covers. Do NOT use them inside the engine to fasten the cam boxes, for example-- all that heat could melt the nylon.

[notmytarga]

I haven't seen any thing llike that. Is it the bore of the nut that is triangular or the cut of the threads? Anyone have a picture of the mystery "oblong locking nut". My intake studs had nuts that have a horizontal cut that looked like it would have a locking function - I have no reason to believe these wern't stock. The cambox nuts were pretty ordinary (other than the barrel nuts of course) with the spring washers under them. Unless I am cautioned strongly otherwise I will reuse these nuts with new spring washers.

I'm willing to change out my washers especially after seeing the M6 ones for the cam thrust plate in pieces when tearing down the engine.

[304065]

Don't throw out the DIN 137B wave washers until you have EXACT replacements in hand. Factory are black oxide, remember that stainless will gall. The inside diameter and outside diameter must be very carefully compared to what you've got. That said, they are available, although not particularly easy to find in black. I would use silver zinc if you are not doing concours.

The nut you saw with the slit, was it copper? This is a standard form of a copper exhaust lock nut although I have seen some zinc plated ones-- these are usually 12mm Across the Flats (ATF, German word is SW, Schlusselweite) to make it easier to get the stacks or whatever on or off. Compare this to the SW13 elswhere in the engine.

Here is what the prevailing torque nuts look like

[notmytarga]

The intake nut wasn't copper. Thanks for the washer recommendation, hopefully the spring washers from Pelican will be good replacements. I have kept all my hardware cleaned, bagged and labeled to do these comparisons prior to accepting and using replacements.

Thanks for the picture. I have not run across that gem.

Perhaps I'll post a picture of that intake nut and the other ones I am toiling over. But a photo session will have to wait till I'm back in the garage.

[euro911sc]

John is the very helpful hardware man I never thought about the torque issue on prevailing nuts... Thought provoking for sure. Though, I have yet to maul threads or break a stud off.

Best regards,

Michael