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Old 04-04-2013, 11:13 AM   #46
supershaft
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Quote:
Originally Posted by Paul_Rochdale View Post
Screw the damned torque wrench, just do them up hand tight and then a gentle tweek with the correct spanner. Never had one come loose. Never had problems with the threads but once bodged like those images, an expensive and more thorough solution is required as has been explained.
I have experimented with how tight they have to be. I turned my exhaust nut wrench into a torque adapter. They have to be almost as tight as some of the factory specs or the headers will creep out of the head a quarter inch.

supershaft screwed with this post 04-04-2013 at 11:33 AM
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Old 04-04-2013, 07:18 PM   #47
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Originally Posted by Plaka View Post
Talk to Carl...around here somewhere.
I'm still here...

Airhead cylinder head exhaust thread issues should probably have its own 'sticky' thread.

So, getting this thread back on the subject of damaged exhaust threads and not how they got to that point here is some info that was previously posted on the different types of damaged thread repairs.

For those considering the repair via cutting threads on a lathe, depending what model head you will be repairing, I expect it will take most people more than an hour to get the part set on the lathe and capable of actually cutting threads. It is one hefty piece hanging off that spindle to attempt to spin and cut threads simultaneously.

I still consider the best method to repair the threads is having the head removed form the engine, remove the damaged threads, weld and then lathe cut new threads.

Carl

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Carl screwed with this post 04-04-2013 at 08:05 PM
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Old 04-04-2013, 08:00 PM   #48
Airhead Wrangler
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Originally Posted by Carl View Post
I still consider the best method to repair the threads is having the head removed form the engine, remove the damaged threads, wled and then lathe cut new threads.
Just curious, do you have any photos of how you load a head in a lathe? I'm still trying to wrap my head around that part. Nice looking repair.
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Old 04-04-2013, 08:01 PM   #49
R100RT Mark
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Originally Posted by Bill Harris View Post
Seconded. A repair like that is as good as new. Too bad the OP's exhaust stub was bodged, but that happens. The annual ritual is to undo the nuts, clean off the threads with a BRASS wire brush, apply Anti-Seize generously and tighten them up. The Book say snug to 109 ft/lbs or so; I do them to a double-grunt.

--Bill
Curious. What is the ball park cost of getting someone like Randy Long to do this work?
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Old 04-04-2013, 08:24 PM   #50
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Originally Posted by Airhead Wrangler View Post
Just curious, do you have any photos of how you load a head in a lathe? I'm still trying to wrap my head around that part. Nice looking repair.
Well, based on you and I had a word sematics discussion in the past... I'll still fo go for it. I don't 'load' the head in a lathe. I attach the head to a custom fixture that threads onto the lathe spindle. Ken saw it when they were visiting us last year. The fixtures are different for the various series of heads. The R69/R69S heads require their own fixture design. Maybe some people have a 'one size fits all' fixture. I don't. Think lathe face plates and that will allow your head to wrap around all the ideas for lathe fixturing. I have fixtures for doing the welding separate from doing the lathe turning. It is crucial to have the fixture and spinning process just right or else chatter and vibration will be your worst enemy. The trick is to do some of the process manually and some under power. My latest processes used for the repairs are based on what I learned from the Maestro. One must give credit to the Maestro who so kindly took the time to allow me to review and learn his methodology.

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Old 04-04-2013, 08:34 PM   #51
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Is it some sort of expanding center that goes into the exhaust port? Do you have some sort of live center to support the back or is it just supported on the drive side?
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Old 04-04-2013, 08:41 PM   #52
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Originally Posted by Airhead Wrangler View Post
Is it some sort of expanding center that goes into the exhaust port? Do you have some sort of live center to support the back or is it just supported on the drive side?
Spindle side. Some of the issue is such that the ID bore and end face are generally part of the repair. So the feasibilty of using the tailstock can be a moot point. Also, sometimes even stubby is gone so then that is a real game changer. Part of the trick is indicating the part so the threads end up with the correct final positional placement as from the factory. I get heads that have been repaired from other shops that are not on the original center line. That must make for an interesting chore of getting the exhaust pipes to enter the two bores as required. Yet there are plenty of ways to do these repairs. One has to have the comfort level with whatever method they choose to do it.

Note: to those attempting this repair that consider it child's play, use caution when operating machinery before one ends up w/ a head embedded in your head.

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Carl screwed with this post 04-04-2013 at 08:53 PM
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Old 04-05-2013, 01:06 AM   #53
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Originally Posted by Carl View Post
Spindle side. Some of the issue is such that the ID bore and end face are generally part of the repair. So the feasibilty of using the tailstock can be a moot point. Also, sometimes even stubby is gone so then that is a real game changer. Part of the trick is indicating the part so the threads end up with the correct final positional placement as from the factory. I get heads that have been repaired from other shops that are not on the original center line. That must make for an interesting chore of getting the exhaust pipes to enter the two bores as required. Yet there are plenty of ways to do these repairs. One has to have the comfort level with whatever method they choose to do it.

Note: to those attempting this repair that consider it child's play, use caution when operating machinery before one ends up w/ a head embedded in your head.

Carl
Whack off stub with a chainsaw. Set up on faceplate with a BIG angle plate using the head bolt holes and two hollow bushings. (or bolts and pins in a fixture) Rough center with a cone or turned bushing in the tailstock. Finish center with a Last Word set up in the tool holder. Run thasst on the remains just above the ID shoulder. Face then cut a shoulder for the pipe to be welded. Cut mating shoulder on extruded pipe. Weld. Cut ID, OD and face. Thread.


Or you could just mold new threads with some JB weld. Partall paste and PVA on the inside of the nut.
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Old 04-05-2013, 04:19 AM   #54
Bill Harris
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Originally Posted by Carl
...I don't 'load' the head in a lathe. I attach the head to a custom fixture that threads onto the lathe spindle...
Conceptually, that is how I can see doing it. But there are undoubtedly a LOT of pesky little details in the fixture and setup that can drive one bonkers. Not for the faint of heart, nor of dual left thumbs.

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Old 04-05-2013, 02:27 PM   #55
danedg
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Originally Posted by R100RT Mark View Post
Curious. What is the ball park cost of getting someone like Randy Long to do this work?
Around $125..
If you need valvework, milling, that's a horse of a different color
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