valve cover studs

Guido · Sep 10, 2011

Are the valve cover studs American or British thread?
I am most concerned with the thread on the nut side as it is boogered up and I need to chase the threads in the nut and on the stud.

Guido · Sep 10, 2011

Thread sizes should be listed in the tech section, no?

DogT · Sep 10, 2011

I would like to know too. May depend on the year, I think at some point they went to UNF on some parts in the engine. That said, a 1/4-20 UNC will fit in the head on the exhaust covers, but it may be a 1/4-20 BSW. The only difference is the thread profile. The thread on the stud for the crown nut is probably a 1/4-26 BSC/CEI. I'm guessing at all this. Maybe someone really knows. You can easily put a 1/4-20 Button head Allen with a nice washer on the valve cover and forget the crown nut, not that I've done that, I've seen it done.

Dave
69S

aceaceca · Sep 10, 2011

I did it. Just recently I was checking ex clearance and the stud twisted off. Came out easily thank goodness. I put a 1/4 bolt in it's place. Seemed to be exactly same thread. Went in slick as a whistle.

L.A.B. · Sep 10, 2011

Guido said:
Are the valve cover studs American or British thread?

The cover stud part number (T2252/NMT2252/06-7582) and nut (T2085/NMT2985/067552) goes right back to 1955 so there's no evidence to suggest that the 1/4 - 20 Whitworth stud thread (into the head) ever changed to 1/4-20 Unified. The nut and nut-end of the stud has always been 1/4-26 (BSC = Cycle thread)

Guido said:
Thread sizes should be listed in the tech section, no?

Fasteners/thread types listed here by part number : http://stainlessbits.com/link12a.html

This list of British thread types and sizes is in the tech sticky: http://www.britishfasteners.com/threads/index.html

DogT · Sep 10, 2011

LAB,
I'm not trying to pick nits here, but I am always confused, as usual. The list at stainlessbits.com is somewhat confusing. I look in my Spares book and the timing cover screws, at least 2 of them are listed in the picture as items 134 and 135, the corresponding parts in my book is 24689 and E.6980. In the stainlessbits page, the 24689 is listed as 1/4-20x1 3/16" UNC, and the E.6980 is listed as 1/4-20x1" BSW. Since those 2 screws both go into the timing cover, I doubt if there are 2 different threads in the same timing side case? I'm not trying to be an A$$hole (but maybe anal), I'm just trying to figure it out. I seem to see stuff like this a lot. However I replaced my timing cover screws with Allen head 1/4-20 UNC and they seem to be working fine. Gearbox screws are another item and definitely not UNC.

Dave
69S

Rohan · Sep 10, 2011

L.A.B. said:
The cover stud part number (T2252/NMT2252/06-7582) and nut (T2085/NMT2985/067552) goes right back to 1955

so there's no evidence to suggest that the 1/4 - 20 Whitworth stud thread (into the head) ever changed to 1/4-20 Unified. The nut and nut-end of the stud has always been 1/4-26 (BSC = Cycle thread)

They actually go back before 1955, they were the same right back to the first 500cc Model 7 Twin in 1949.
You just need an earlier parts book - and be mindful the parts numbering system has changed. A few times.

Cheers.

L.A.B. · Sep 10, 2011

Rohan said:
They actually go back before 1955, they were the same right back to the first 500cc Model 7 Twin in 1949.
You just need an earlier parts book - and be mindful the parts numbering system has changed. A few times.

I don't need anything. And I did check.

http://www.norvilmotorcycle.co.uk/cylhead.htm

067582 STUD - ROCKER COVER - FRONT - ALLOY HEADS ONLY - 1956 ONWARD

012952SS STUD - ROCKER COVER - FRONT - IRON HEADS ONLY - 1948-1955

L.A.B. · Sep 10, 2011

DogT said:
LAB,
I'm not trying to pick nits here, but I am always confused, as usual.

There's obviously going to be the odd discrepancy when different threads have the same tpi.

Guido · Sep 10, 2011

I was holding off for as long as I could but I am now forced to purchase a set of CEI taps and dies.
It ok as I am a freak for new tools.
The stud,,,,standard on one end and British on the other? Sheeeeeesh, SOB, damn it, WTF.
Now, if only my lath would cut Whitworth threads. I'd be all set!

L.A.B. · Sep 10, 2011

Guido said:
The stud,,,,standard on one end and British on the other? Sheeeeeesh, SOB, damn it, WTF.

?

British Standard thread one end (1/4W), and British standard thread (1/4 Cycle) the other end.

DogT · Sep 10, 2011

Guido said:
I was holding off for as long as I could but I am now forced to purchase a set of CEI taps and dies.
It ok as I am a freak for new tools.
The stud,,,,standard on one end and British on the other? Sheeeeeesh, SOB, damn it, WTF.
Now, if only my lath would cut Whitworth threads. I'd be all set!

If the stud is BSW one one end, undoubtedly it's BSW on the other??? I've never been able to see the difference even with a magnifier in the 1/4-20 BSW and the 1/4-20 UNC, but the profile certainly is different by the book.

Your lathe would probably cut BSW threads if you have the right cutter or angle it right, I don't know about these things?

Dave
69S

L.A.B. · Sep 10, 2011

DogT said:
If the stud is BSW one one end, undoubtedly it's BSW on the other???

One end is Whitworth (the coarse end into alloy) and the other end Cycle thread (1/4 - 26).
http://www.norvilmotorcycle.co.uk/067582.htm

DogT · Sep 10, 2011

Maybe we should start a new thread about putting UNC bolts into BSW threads? Anyhow, I give up. If it works and doesn't come apart I guess that's good enough for me. I'm not going to go the Galileo route, I'm too old for that.

Dave
69S

Rohan · Sep 10, 2011

L.A.B. said:
http://www.norvilmotorcycle.co.uk/cylhead.htm

067582 STUD - ROCKER COVER - FRONT - ALLOY HEADS ONLY - 1956 ONWARD

012952SS STUD - ROCKER COVER - FRONT - IRON HEADS ONLY - 1948-1955

Click to expand...

There is something slightly screwy there - the iron head only went to 1954, and the alloy head appeared for 1955.
So Norvils years are out by a year.
The threads for the nuts, and the nuts, are all the same, right back to 1949.

Stainless steel valve cover studs eh, who'd a thunk.....

DogT · Sep 10, 2011

Boy, we all have different problems, don't we?

Dave
69S

Guido · Sep 11, 2011

DogT said:
Boy, we all have different problems, don't we?

Dave
69S

No more problems here as far as the studs go, I just went down to my local hardware store and bought four 1/4x20 chrome Allen head bolts, ran a 1/4x20 tap in the stud holes and solved my boogered up thread problem.
They are decorative and match all the other Allen head bolts.
I guess the whitworth and SAE were close enough.

All this because I just put on new head gasket.
Now if I can only figure out why it won't start I'll have it made.
Stupid Boyer crap!
Looks like I'll be buying the Tri-Spark ignition.
But that's another thread.

cash · Sep 11, 2011

Buy a 'ZEUS' book, it's a cracking little engineers chart book. The Imperial version has been superseded by a Metric version but still contains the major imperial forms. You'll find most if not all small threads with the same diameter and TPI will happily interchange.The 5 degs difference in thread angle is accommodated by the running clearance and usually isn't a problem.

Cash

L.A.B. · Sep 11, 2011

Guido said:
I guess the whitworth and SAE were close enough.

60°Unified thread
http://www.gewinde-normen.de/en/unified ... hread.html

55° Whitworth thread
http://www.gewinde-normen.de/en/whitwor ... hread.html

Guido said:
Stupid Boyer crap!

Yes, cheap as chips electronic items should be built to last for ever, not just for maybe 20 years or so.

L.A.B. · Sep 11, 2011

cash said:
Buy a 'ZEUS' book, it's a cracking little engineers chart book.

And the thread data is available on the Internet these days.

valve cover studs

Guido

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aceaceca

L.A.B.

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DogT

Rohan

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