Exhaust studs question

[Scottjeffrey]

Hi. I am re-installing new exhaust studs into the head. Because of things I've read here advising to 'just snug them up", (I am using permeated red thread sealer as advised), I have stopped working on them to ask this question. I cleaned the holes many time with brake cleaner until q-tips came out clean. What has given me pause is that they are requiring a good amount of force to thread in (one with sealer on it and also one without I tried. Using double nuts to install, I found myself concerned about hurting the head. Anyone else find them requiring a fair to good amount of force? The old ones' removal was unremarkable.

Many Thanks,

Scott

[TobyB]

This is where you make SURE they're M8, and not 5/16"!

 

And then yeah, with a firm hand, run them in.  In one motion,

because if they are very clean and a tight fit,

that threadlocker kicks pretty darned fast!

 

I'd try one dry, first, and if it went much over 10 ft- lbs,

triple check everything.  I DO have to double- nut them sometimes-

if the nuts slip, that's another indication that they're too tight,

or something's wrong.

 

t

does it mostly by feel

 

 

[Son of Marty]

Take the new studs and lay them along side of the old one with the thread peaks of one set into the thread valleys of the other ans they should match the whole length of the threads in pitch and depth of the threads. They are a tight fit but we'll never be able to tell what your feeling is tight over the interwebs. 

[Scottjeffrey]

1 hour ago, TobyB said:

This is where you make SURE they're M8, and not 5/16"!

 

And then yeah, with a firm hand, run them in.  In one motion,

because if they are very clean and a tight fit,

that threadlocker kicks pretty darned fast!

 

I'd try one dry, first, and if it went much over 10 ft- lbs,

triple check everything.  I DO have to double- nut them sometimes-

if the nuts slip, that's another indication that they're too tight,

or something's wrong.

 

t

does it mostly by feel

 

 

 

1 minute ago, Son of Marty said:

Take the new studs and lay them along side of the old one with the thread peaks of one set into the thread valleys of the other ans they should match the whole length of the threads in pitch and depth of the threads. They are a tight fit but we'll never be able to tell what your feeling is tight over the interwebs. 

Thanks Guys. These are what I bought, BMW Stud Bolt (M8X28Zn)(M3 M5 M6 ) - Genuine BMW 07119908368. Here is a pic side by side, looks right to me. I am at a loss. Scared to 'crank them in'. One million thanks - Scott

[Son of Marty]

If the threads match and it sure looks like they will then I would agree with Toby's 10 ft/lbs estimate I do it by feel also but the sure won't thread in very far by hand they need to be a snug fit to compensate for the expansion of the aluminum head  vs the steel stud. 

[Scottjeffrey]

3 minutes ago, Son of Marty said:

If the threads match and it sure looks like they will then I would agree with Toby's 10 ft/lbs estimate I do it by feel also but the sure won't thread in very far by hand they need to be a snug fit to compensate for the expansion of the aluminum head  vs the steel stud. 

I followed your advice above 'laying' one into the other and they match perfectly. Thanks again!

Edited December 7, 2019 by Scottjeffrey

[stephers]

run a tap thru them to make sure the threads are ok    sometimes when the stud holes are completely dry, especially aluminum, they can be tight

[jimk]

I believe the head when new had the studs installed with a class 3 interference fit.  The hole is threaded with a class 3 tap and the stud a std thread.  Once installed and removed, the fit gets looser.  Sometimes there is still some interference to the fit.  Running a std tap for sure will loosen it up.  Apply some sealant and run them in.

[Scottjeffrey]

4 minutes ago, jimk said:

I believe the head when new had the studs installed with a class 3 interference fit.  The hole is threaded with a class 3 tap and the stud a std thread.  Once installed and removed, the fit gets looser.  Sometimes there is still some interference to the fit.  Running a std tap for sure will loosen it up.  Apply some sealant and run them in.

I jimk, Thank you for your help. I just purchased this to address the situation.

https://www.amazon.com/gp/product/B000XJ48V0/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

That is quite a piece of data you shared. Very cool.

Thanks again,

Scott

[Son of Marty]

I agree with Jim it should be a tight fit and I wouldn't run a standard tap through those holes instead take a old stud and a triangle file or thin cutting disc and cut 1 or 2 slots down the stud cutting the threads to there base and use that to clean up the threads.

[jimk]

I am not particularly fond of removing metal from anywhere.  Once removed, it becomes challenging to get it back on!

[Son of Marty]

Scott I would not use that set in this case I'm sure they will be for a standard (class 1?) fit But at the same time for that price I would save it most other taped holes on a 02 just my opinion.

[Scottjeffrey]

44 minutes ago, Son of Marty said:

Scott I would not use that set in this case I'm sure they will be for a standard (class 1?) fit But at the same time for that price I would save it most other taped holes on a 02 just my opinion.

 

51 minutes ago, jimk said:

I am not particularly fond of removing metal from anywhere.  Once removed, it becomes challenging to get it back on!

Wow. I thought this set was not a tap but a chaser, much less aggressive than a tap. My mistake. Thanks for the help in avoiding unnecessary metal removal. What tool would you recommend if any, to clean the threads in the head?

Best Regards,

Scott

Edited December 7, 2019 by Scottjeffrey

[Son of Marty]

Scott that is a chaser set and ment to clean and restore as opposed to taping  but i'm pretty sure it will be for standard fit threads and will restore any hole to that standard, as Jim said these are a interference fit which is much tighter.

[Scottjeffrey]

5 minutes ago, Son of Marty said:

Scott that is a chaser set and ment to clean and restore as opposed to taping  but i'm pretty sure it will be for standard fit threads and will restore any hole to that standard, as Jim said these are a interference fit which is much tighter.

I am cancelling the order, can't afford any extras right now, lol.

 What do you recommend? Forgive me, You suggested above!

 

Thank You,

Scott

Edited December 7, 2019 by Scottjeffrey