Are there exhaust nut thread size variances?

[jimbo]

Are there exhaust nut thread size variances? I have a set of nuts and the thread OD is 1.908" and they seem loose.

 

[Bob Z.]

I just measured a couple from 850 heads and got 1.93".

 

[jimbo]

measure some nuts if you could

 

[dynodave]

Yes there are quite a bit of thread variation. I had done a whole mess of exhaust roses in 2010 while temping in a mechanical calibration lab. Measuring the OD of the thread is of little help. (actually ignorant...) Measuring threads is done with 3 calibrated wired.
I measured nut thread diameter delta .026" and the actual pitch diameter delta .015" (not too good!!)These numbers are not absolutely assured correct since I used the unified formula rather than whitworth and I did not actually verify the angle on the optical comparitor.
And the threads are listed as 1.997x14 and I make them to be 1-15/16"x14NS which may not be correct but my head repairs seem to be OK with the exhaust roses I have access to.

 

[gortnipper]

Are the thread pitches the same on the early ones on the L as on the late ones on the R?

http://atlanticgreen.com/images/exhrose.jpg

The PO put the old style ones on before I got it, and had stripped out the ports so when I had a mate make me some inserts he noted there were differences betweend the two old ones and made the threads to match. He was a tool maker, and I don't know whether or not he was just being pedantic, but I do have two of the newer ones in a box of spares.

 

[dynodave]

I do believe they are meant to be all the same. They will all interchange from a thread stand point only. In my test I used many roses and specifically included from 1949 cast iron head through 1975. The ones in the pix are only one of each type.
Of the small fin variant there is early without out the double strong lug and later with the strong doubled lug.

 

[jimbo]

Dave I'm well aware of the using three wires method, however I do not have any of the wires.Comparing nuts, roses or whatever you want to call them (lockrings per the factory) I think can be done by measuring the OD, the major dia. I'm not setting a machine up to fabricate them. Just trying to get a good set, if there is such a thing. The question is why is there so much difference? I cannot see used ones wearing smaller, there must have been a manufacturing problem over time.Whos got correct sized roses?

http://www.editcnc.com/Thread-Measure.html

 

[dynodave]

"there must have been a manufacturing problem over time"

And does this surprise you in the least? :twisted:

"Whos got correct sized roses? "

The machine shop that makes them for you to your specs/class of thread.

16TPI(sorry for quick substitution)
class 2 .006"
class 3 .0045"

So .015" is not that great but Norton though it was fine for us.
Good luck finding what you desire.

 

[dynodave]

Are the thread pitches the same on the early ones on the L as on the late ones on the R?

http://atlanticgreen.com/images/exhrose.jpg

The PO put the old style ones on before I got it, and had stripped out the ports so when I had a mate make me some inserts he noted there were differences betweend the two old ones and made the threads to match. He was a tool maker, and I don't know whether or not he was just being pedantic, but I do have two of the newer ones in a box of spares.

My tap, 1-15/16x14NS class GH4, cleans up my inserts after welding and ALL roses have gone in slick and easy if the threads are clean. To me they feel snugger than the original heads.
If the machinist did a good guess on his numbers than all the exhaust roses should go in just fine.

ONE caveat!, I have never measured aftermarket exhaust roses so success is not assured

 

[gortnipper]

They will all interchange from a thread stand point only.

Can you expand on what you mean by this? I understand that there are differences in how long the threaded sections insert into the head are, but what are other interchangeability issues?

 

[dynodave]

If some numb skull quote's me "they are the same" they will use 850 nuts on a 750 and then say dynodave "said......"
there fore caveat.

ONLY THE THREADS ARE THE SAME :mrgreen:
As you say not the length of thread

 

[gortnipper]

If the machinist did a good guess on his numbers than all the exhaust roses should go in just fine.

OK, sweet. I will likely give them a go when I swap exhausts... at some point...

 

[johnm]

Big variety from different vendors over the years.

I have a box of them that rattled like crazy from new.

 

[Rohan]

If you get them replated, they can go from quite loose to snug.

You may want to specify a light or heavy plating though.
Too tight may not be a good idea.

Dynodaves pic could useably be downsized a bit .... ?

 

[gortnipper]

Can someone let me know how deep the threaded portion of the old style small-finned nuts are (06-2464)?



I measured my newer 850 style (06-3988) nuts and they are 17mm (0.67") until the shoulder.

 

[Rohan]

Can someone let me know how deep the threaded portion of the old style small-finned nuts are (06-2464)?

I measured my newer 850 style (06-3988) nuts and they are 17mm (0.67") until the shoulder.

A bunch of D12/167 here (= 06 2464) are all between 17mm and 20mm.

Interestingly, the 17mm pair have a 1 mm at least lead in to the threads.
Whether that would/could allow them to tighten better would need some looking at....

 

[gortnipper]

A bunch of D12/167 here (= 06 2464) are all between 17mm and 20mm.

Interestingly, the 17mm pair have a 1 mm at least lead in to the threads.
Whether that would/could allow them to tighten better would need some looking at....

I think you can see the lead in on dynodave's pic and the one on the Old Britts site.

According to British Cyle:

06-3988 NORTON 750 / 850 – 1975 EX.LOCKRING (CHROME-SHORT) .612" (15.5mm) THREADED SECTION

I would have thought the shorter ones were to accommodate the split collets, so I wonder how long the long ones (06-3555) are?

 

[gortnipper]

A bunch of D12/167 here (= 06 2464) are all between 17mm and 20mm.

Interestingly, the 17mm pair have a 1 mm at least lead in to the threads.
Whether that would/could allow them to tighten better would need some looking at....

I think you can see the lead in on dynodave's pic and the one on the Old Britts site.

According to British Cyle:

06-3988 NORTON 750 / 850 – 1975 EX.LOCKRING (CHROME-SHORT) .612" (15.5mm) THREADED SECTION

I would have thought the shorter ones were to accommodate the split collets, so I wonder how long the long ones (06-3555) are?

 

[bchessell2]

I have repaired the exhaust threads for 30 plus years now and the new nuts you buy vary greatly in size. I have found that the norvil bronze nuts seem to be the same as well as machined , not pretend threads like some of the aftermarket ones that vary as much as .010" on the outer diameter. The norvil ones are the long 750 style.As the head heats up they seem to expand and stay tight .
Just my intake.
Bruce

 

[gortnipper]

I have repaired the exhaust threads for 30 plus years now and the new nuts you buy vary greatly in size. I have found that the norvil bronze nuts seem to be the same as well as machined , not pretend threads like some of the aftermarket ones that vary as much as .010" on the outer diameter. The norvil ones are the long 750 style.As the head heats up they seem to expand and stay tight .
Just my intake.
Bruce

Do you guys use the collets on 850s with the Norvilbronze nuts?