exhaust studs

T77911S · 08-09-2015, 11:22 AM

A little worried about the first 2 threads on this exhaust port. You can really see it at the 1 o'clock position.
Anything I can do for this stud. Hate to say it but JB weld it in.

Should I locktite the other studs.

Flat6pac · 08-09-2015, 11:28 AM

You still have a dozen threads that will hold.
Bruce

lelix · 08-09-2015, 11:38 AM

Run an M8x1.25 tap through it to be safe and to clear the remaining threads. Install new stud. (If reusing old studs make sure the threads are clean and free of debris/rust)

turbo owner · turbo owner's Garage

Use a forming tap not a cutting tap

T77911S · 08-09-2015, 02:53 PM

I started to run a tap. It got hard and I did not want to cross cut "new" threads and make what was left weak. When I run the tap into a new non exhaust nut that fits the threads it is like it is cutting new threads in the new nut. The nut still threads the stud like it is good. Just worried that the tap will weaken the threads.

I always try to run a tap and die over threads before putting things back together. I don't know what a forming tap is. I have heard of thread chase but have not been able to find any.

Is there a torque for the stud and what about locktite.

lelix · 08-09-2015, 05:00 PM

Quote:

Originally Posted by T77911S

I started to run a tap. It got hard and I did not want to cross cut "new" threads and make what was left weak. When I run the tap into a new non exhaust nut that fits the threads it is like it is cutting new threads in the new nut. The nut still threads the stud like it is good. Just worried that the tap will weaken the threads.

I always try to run a tap and die over threads before putting things back together. I don't know what a forming tap is. I have heard of thread chase but have not been able to find any.

Is there a torque for the stud and what about locktite.

There will be a variation in the thread profile between the tap and the nut. Whether it's due to machining variations, plating etc. It will always have resistance on the first cut. Alignment is the crucial part, you need to make sure you are dead straight in the bore, the tap will want to follow the damaged threads when you first start it, if you let it, it can go in off kilter in relation to the good threads.
You need to clean up that bore by whatever means you feel comfortable with. A properly aligned and lubricated tap will correct those few threads without an issue. If you have access to one, a thread chaser which is essentially a "dull" tap with a less aggressive cutting profile will also do the job.
When you will run the tap, the "damaged" threads you see in your picture will inevitably be weakened since the tap will cut some material out of them in order to bring them back into alignment with remaining healthy threads. If you do not, you risk cross threading the bore even further. Just don't go overboard with the tap.
A forming tap, which is more of a specialty tool, displaces, or pushes the metal to form a thread rather than cut the metal like a regular tap.

sorry for the long winded response, it really looks like some minor galling of the upper threads and should be a straight forward fix

T77911S · 08-10-2015, 02:33 AM

i started to tap it and i think that is what messed the threads up.
the stud still goes in fine, i just dont wnat it to pull out.

theiceman · 08-10-2015, 05:00 AM

you have a ton of thread you will be fine ..
In situations like this i simply use a brand new steel bolt of the same thread and slowly work it back and forth with oil . Works just like " forming tap" noted above. As pointed out allignmnet is crucial. I think you will be fine.

Good question about the new studs though , i removed all mine as i am putting longer ones in for the thick flange exchangers, should the new studs be loctited in or will the heat of the exhaust melt the locctite anyway ?

chris_seven · 08:24 AM

Quote:

Originally Posted by turbo owner

Use a forming tap not a cutting tap

Cold Forming Taps aren't really any better than a cutting tap both of them will reduce the class of fit of the thread.

I would agree cold forming taps don't cut but they work by cold deforming the material surrounding the tap.

I would use an ARP Thread Chaser as first choice, these devices are far less intrusive than any type of tap.

LUFTKUL · 06:54 AM

Thread chaser with tapping oil should work it out. Slow and straight, back and forth. Pull it out completely in the beginning to clear out any shavings that might appear from the first couple of threads.

I wouldn't use Loctite, but I would use anti-seize.

scarceller · scarceller's Garage

You can also timesert the threads. I have this kit for those threads:

Timesert Thread Repair Insert Kit Tools M8x1 25 Auto Car Engine Tools | eBay

You can timesert that thread easily without removing the motor.

T77911S · 08-10-2015, 08:22 AM

i was trying to avoid timeserts until the heads came off.

i have looked for thread chase kits but could not find any.

is there a torque value for the studs.

chris_seven · 08-10-2015, 08:55 AM

Quote:

Originally Posted by T77911S

i was trying to avoid timeserts until the heads came off.

i have looked for thread chase kits but could not find any.

is there a torque value for the studs.

The Official ARP Web Site | Thread Cleaning Chasers

tharbert · tharbert's Garage

A number of folks have posted here that they use an old head stud grooved with a dremmel to clean/dress threads...something akin to this chaser:

(pic from cgarr here)