Which exhaust nut for which head insert ???

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OK, this is a "type" of exhaust port thread, but along lines I haven't seen before. I have two 850 motors I hope to build soon, gathering the parts together now. One has an RH10 head, and the other an RH4. The RH10 has what appear to be steel inserts threaded in; with two small roll pins at 180 degrees from eachother to "peg them in place" ... I guess. The RH4 should be with Jim C getting the inserts that he makes, ( silicone bronze ?) ... so I don't have pics of it. Maybe he will post ?

Questions, should the RH10 use the stock steel exhaust nuts ??? (I would think like metals will "gall" each other) Or, should I use some bronze exhaust nuts. ( I have them on my 750 that has good stock port threads and they work great.) Or ... should I use something else ?

On the RH4, should I use steel, bronze, or something else ? Comments please.

Which exhaust nut for which head insert ???


Which exhaust nut for which head insert ???


Which exhaust nut for which head insert ???
 
Whether bronze or steel I always use a good high temp anti sieze. One might think that lubing the thread in this manner may encourage the exhaust nut to loosen. This is contrary to reality. Just like with plumbing, pipe dope is not a sealant but a lubricant.
With lubed threads all the pressure of torquing will directed to the crush washers. This also reduces the need or desire to overtighten and cause damage to the head. Sound pactices of snugging every few hundred miles is encouraged.

I think people damage their exhaust thread by not using high temp lube and are force to over tighten with long pipe wrenches and breaker extensions.

Lube em up and don't OVER tighten.
 
comnoz said:
Wit stock aluminum threads there is probably a small advantage in using the bronze nuts because they expand at a rate similar to the aluminum head so they tend to stay tighter. With the bronze inserts I would stay with steel nuts to avoid the friction caused when like metals rub against each another.
An interferance fit means the insert is slightly larger than the hole it is being screwed into when they are at the same temperature. To make it fit I heat the head and cool the insert before I thread them together. Locktight sets up very fast when it gets hot . Sometimes faster than I could screw the insert into the hole. Then I ended up having to bore out a half installed insert that wouldn't move anymore and starting over. There is no such thing as overkill when it comes to keeping an exhaust attached to a Norton head. Jim
 
I would generally avoid using like metals on threads that may have a tendency to "work" on each other but steel is pretty tough and with a little antisieze they may be fine. I can't say I have any experience with steel exhaust thread inserts. I would be worried that the insert would come loose in the head. I use hard aluminum bronze as the expansion rate is similar to the aluminum.
I did take a couple shots of your head before I started the repairs, just so I could remember how not to do it. There were eight screws in this side and several more in the other side. Jim [not Nortiubuells head, but one received last week]

Which exhaust nut for which head insert ???
 
So what torque spec do you folks use for exhaust nuts? I use 60 lbs-ft myself, tightened to that level initially and then hot and running a couple times. After a few of those they never seem to loosen (I use Suzuki GS1000 crush washers and yes I goop up the threads with antiseize).
 
I can't say that I have ever used a torque wrench on an exhaust nut. I use a 12 inch pipe on a c-spanner and tighten it as tight as I can get it without hurting myself or damaging the nut. Probably more than 60 ft lbs. Jim
 
Thanks Jim. I use a torque wrench 'cause without one my general rule is "torque 'er 'til she strips, then back off 1/8 turn...." Investing in a couple torque wrenches has probably saved more than a few sets of threads around Maison BrianK....
 
Hello all- the only thing my small mind will add is that I safety wire my exhaust nuts. A small hole in the nut fin, wired to the acorn nut on top of the cylinder. Actually keeps them from rotating loose.

Yes, I safety wire my nuts. Been doing it a long time, too.

Safety first!
 
Hello askdoctorday, I ALSO safety wire my nuts, thru one of three holes I drill at 120 degrees on each nut. And, then wrap it around the acorn nut. I cringe at how many cylinder heads I see have a hole drilled in a fin to do this. Cheers.
 
Pat, Your cylinder head was a piece of cake. Nice to get one now and then that just needs threads.

Which exhaust nut for which head insert ???


A cone locates the port so the pipe will be lined up.

Which exhaust nut for which head insert ???


Then a 1 inch carbide spirals into the hole to prepare it...

Which exhaust nut for which head insert ???


For a thread mill.

Which exhaust nut for which head insert ???


Then the head is heated to 250 degrees with hot air and the insert is screwed in.

Which exhaust nut for which head insert ???


The a 3/4 radius mill trims it to length and cleans it up.

Which exhaust nut for which head insert ???


One side is done.

Which exhaust nut for which head insert ???


Now just rinse and repeat. Jim
 
Wow ... I am simply "awed' by this kind of workmanship. And your fantastic pictures really tell the story Jim !!! Perhaps when I get the head, I'll start the 850 motor rebuild and post a thread with some pics ??? Strictly an "amateur" build of course, but it might be entertaining for some. I took three days reading grandpaul's build of his latest monoshock, and luved every word of it !!! I read it like I was sipping expensive wine and savoring every drop, rather than guzzling it like a cheap beer as fast as possible ...
 
askdoctorday said:
Hello all- the only thing my small mind will add is that I safety wire my exhaust nuts. A small hole in the nut fin, wired to the acorn nut on top of the cylinder. Actually keeps them from rotating loose.

Yes, I safety wire my nuts. Been doing it a long time, too.

Safety first!

Same here and never have a problem with them,
 
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