Removing Heat Exchanger Nuts - Thanks John Walker

cds72911 · 12-11-2001, 05:12 AM

I guess the title says it best. Thanks John Walker for the great advice.

For the archives: I was able to remove all of the fasteners on my heat exchangers without much hassle. I applied penetrating fluid and let it sit, applied more, tried them all, removed the ones that would come out. For the ones that were stuck I rapped them a couple of times with a hammer and brass drift, then took out the oxy-acetylene torch and heated each until it was cherry red. At that point they came off easily - incredible!!

I think it helped that the engine was on an engine stand and rotated such that the heat exchangers are on top. Access is much improved this way.

Thanks!
Charlie

12-11-2001, 05:25 AM

The "Gas Wrench" triumphs again!

Jdub · 12-11-2001, 05:29 AM

Charlie:

Will you be pulling those studs and repacing them?

Jw

cds72911 · 12-11-2001, 05:39 AM

Well, I already removed about six of them...

They came out with the nuts that were solidly rusted to them. So, I'll replace those for sure. Depending on whether the rest of them look okay I may just run a tap down them and reuse them. To be honest I hadn't thought much about it.

Is there a compelling reason either to replace them or not?

Thanks,
Charlie

Jdub · 12-11-2001, 05:53 AM

Charlie:

Just did a quick search but did not find the information I expected (bad keywords?). Anyways, there was a thread about replacing these exhanger studs with a larger diameter set as the old ones, once rusted up, are just looking for an excuse to do it again.

Since the stud is hip tapered (think hourglass) it is likely they might/will break. A stud puller from a reputable rod shop will work, but you may find yourself wanting at the least to replace all studs and be done with it.

If anyone can find the thread where the exact stud size/pitch etc. was discussed and post that link here I'd be much appreciative as I am going to embark on the same procedure.

Jw

cds72911 · 12-11-2001, 06:15 AM

Thanks JW,

I guess I'll replace them then.

I've got a stud remover that works with a rachet that might work but I've actually had better luck with the "double nut" method. One additional nice thing about the double nut method is that it is non-destructive in case you need to reuse the stud for some reason.

With the setup you describe, do you install timecerts with a larger thread size and go to a bigger stud or reuse the exisiting holes with a normal size stud? If I go bigger I may have to ream the holes in the SSIs to match.

Thanks,
Charlie

Jdub · 06:23 AM

Charlie:

Now I am in over my head. I can't say for sure but do hope that someone with the right answer might pipe up. Your question on opening up the current hole versus 'certs is THE question.

I will perform another search to see what I find. Do please await a more knowledgable poster than myself before you proceed!

Jw

AHA: Here we are:

http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=9495&highlight=Oversize+stud

Clark Griswald · Clark Griswald's Garage

Don't timecert unless you need to. Needing to means the stud snapped off and you have no choice but drilling it out.

If you do timecert, replace with the stock size stud. 8MM 1.25 thread pitch. You can get new studs from the dealer cheaply (maybe Pelican too).

You can also get special studs that have 10MM on one side and 8MM on the other. In this case, you drill and tap the head for 10MM, and leave the exchanger flange alone.

Both methods work. But the timecert is more durable.

In any case, be sure to use anti-seize compound on both threaded sections when re-installing.

FYI, my experience with the socket style stud extractors is they don't work. The stud only snaps off when it is REALLY tight, and the socket style can't grip stud tight enough to get it out.

911pcars · 12-11-2001, 08:42 AM

New steel studs are better than the old, corroded ones, even with antiseize applied, but future-thinking owners may wish to search for stainless steel versions (washers and nuts too) and forget about corrosion problems. I wish I did when I had it apart. While stainless doesn't have the ultimate tensile strength of steel, this is not of concern in this application.

Regards,
Sherwood Lee
http://members.rennlist.org/911pcars

Oldporsche · 12-11-2001, 12:39 PM

Since not a lot of fastening strength is needed, I will try to use brass nuts on the next application. I think I can find some in metric. They should be cheaper and easier to remove with a wrench/torch if necessary.

Good luck,
David Duffield

82SC · 01:24 PM

in my tech article about back dating the heat exchangers I think I gloss over some solutions...

I think it was NICKSHU that had a jig that he offered me to use if a stud broke...it lets you drill it out...

seach for headstud, heat exchanger backdate etc... and you will get a plethora of threads about this...

I think most people heat the head and use the double nut locking system to screw the bolt out...then just straight replacement...

I think nickshu's jig works out well if you snap them sine it lets you drill them out and no time certing...

also snap on tools has some special tools to take out studs and take out broken studs...again these should be covered in past threads...I do not know the info off the top of my head...

budget solution would be reverse direction drills...but that is a cheap and dangerous way

I have not had first hand experience, so Iam sure someone will pipe up who has done this...this is the info I gathered before I attempted mine...

hope this is helpful

PS start a new thread with the title "help broken head stud...okay not really but replacement info needed"

they will bum rush you...lots of people have gone through this

RoninLB · 12-11-2001, 07:08 PM

I use stainless nuts on exchanger to head because Competition Engineering did the head work. Everything else on exh. gets stainless nuts, bolts, and washers. I have to "seat" the torque by tightning after rides a few times untill it stops tightning. I don't over torque. The heat/cold cycles have less effect on stainless after they are "seated". Then I put the wrench to them every oil change to check them. I use silver high temp anti-seize. There are different grades of stainless. Not an expert, only salt air crazy, but IMHO a magnet is best way to check out what I want. If it will not take a magnet then great quality. If it takes magnet a little then OK to use. If it takes magnet a lot then NG. Marine supply is my depot or mail order.

rcwaldo · 12-11-2001, 07:38 PM

I am kinda in the same boat with my 2.7 rebuild. I broke two exhaust studs removing my exchangers. I am sending them out for EDM extraction. I hear its about $25 a stud, but money well spent IMHO. I will also replace ALL exhaust studs. They become brittle after all the heat cycles that they see.

I also recommend using a nickel based anti-seize. Much better for high heat applications.

I just hope I can get the remainder of the studs out w/out breaking them. Wish me luck!!!!!!!

Chris