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Technical To weld or not to weld?

Discussion in 'Traditional Hot Rods' started by Shawn Wildman, Aug 31, 2020.

  1. Shawn Wildman
    Joined: Jul 8, 2018
    Posts: 33

    Shawn Wildman

    I just bought a semi-finished project 1941 pickup. The original owner installed a slip fit exhaust system all the way from the headers back and EVERY joint leaks, BAD. I'm 99.9% sure he didn't use any sealer anywhere. I've tried to remove the system and put it back together with sealer, but only the joint at the header will give at all but I can't get any of the other joints apart.

    Should I go ahead and have a shop weld it all together or is there a trick to getting these joints apart? I don't want to weld the exhaust to the headers, I'll have the shop either keep a slip joint or weld in a bolted joint.
    loudbang likes this.
  2. I like to weld exhaust systems or use band clamps. muffler clamps joints are harder to separate than a weld. IMO
    bchctybob, loudbang and ct1932ford like this.
  3. squirrel
    Joined: Sep 23, 2004
    Posts: 47,974


    Does it have u bolt clamps? If so, did you try just tightening them a bunch more?

    Sent from my Trimline
    Cosmo49 and VANDENPLAS like this.
  4. 6sally6
    Joined: Feb 16, 2014
    Posts: 1,403


    If the pipes are rusty you WILL NOT get a good weld on them.
    If not........weld'em!

  5. Shawn Wildman
    Joined: Jul 8, 2018
    Posts: 33

    Shawn Wildman

    I did, and the metal creased and just started leaking at the creases.

    Pipes are in good shape, so welds should be ok.
    loudbang likes this.
  6. BamaMav
    Joined: Jun 19, 2011
    Posts: 4,741

    from Berry, AL

    Get some of the band clamps and throw the U bolt clamps away. The band clamps will conform to the pipe and seal it. Look on eBay, there are several sellers on there.
    JC Sparks and loudbang like this.
  7. gene-koning
    Joined: Oct 28, 2016
    Posts: 2,299


    If the pipes are leaking at the clamps and have been for a while, welding over the places where the exhaust has been leaking could be a pita.

    I've had more issues with band clamps leaking exhaust then I ever had with the U clamps leaking. I'm thinking that if the U clamps are leaking, the pipes were probably not inserted far enough inside, or the U clamps are incorrectly positioned. Gene
    loudbang likes this.
  8. Budget36
    Joined: Nov 29, 2014
    Posts: 5,839


    Just to be sure, all the upstream pipes are inserted inside the downstream pipes, correct?
    belair, loudbang, flatford39 and 2 others like this.
  9. alchemy
    Joined: Sep 27, 2002
    Posts: 16,581


    Just drive faster and you'll never smell the fumes. o_O

    I thought I'd be smart and use a slip fit pipe over the end of the headers on my sedan. I knew I'd have to take it apart again some day. When that day came I found the joint was as tight as if I welded it. It took much yanking and IIRC some air chisel work to remove it. But some hammer/dolly and it was usable again.
    Apache Albert and loudbang like this.
  10. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,174

    from illinois

    Like GeneKoning said , probably a poor job of assembly , to disassemble a uclamp joint , use a torch to heat the joint , then a bit of persuasion they'll usually come apart , 'course if some gorilla got over zealous with an impact & overtightened them you many not get them apart!
    bchctybob and loudbang like this.
  11. You can try double clamping with opposing new clamps.
  12. el Scotto
    Joined: Mar 3, 2004
    Posts: 4,357

    el Scotto
    from Tracy, CA

    Wrap 'em in exhaust bandages, available at your local auto parts store! :eek:
    loudbang likes this.
  13. Weld them and the leaks will be gone. HRP
  14. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 1,848

    from Brooks Ky

    Problem with trying to weld them is that if they have any kind of sealer jammed in the joint it will play havoc with the weld. If rust or exhaust residue is there, it can play havoc too. Best thing is to unbolt the pipes at the exhaust manifold or hedder connection and get it out from under the car. Then you can heat and twist them with one end in a vise. The clamps may have put indentions in the pipes making them difficult to get apart but not sealing properly.
    Once you get it all apart, clean the connections with an electric wire brush. Then fit them in place again and weld.
    If you are a decent welder, you can also make some rings out of exhaust pipe and split them like a lock washer. Put them around each leaky joint and weld both ends and the split.......kind of a "bandaid" approach. Not pretty but effective.
    thintin and loudbang like this.
  15. Beanscoot
    Joined: May 14, 2008
    Posts: 1,893


    I've MIG welded up a few exhaust systems that were old, rusty and generally crappy. It looks awful, but seems to seal quite adequately.

    Years ago I would braze them, that also worked fine on crappy old pipes.
  16. chevyfordman
    Joined: Oct 4, 2008
    Posts: 987


    I like to weld in flanges.
    Crazy Steve and loudbang like this.
  17. Matt Miller
    Joined: Jul 22, 2020
    Posts: 167

    Matt Miller

    Rip it out. Throw it away.
    belair and scotty t like this.
  18. jaracer
    Joined: Oct 4, 2008
    Posts: 821


    Interesting, when I worked in a dealership back in the early 70's we installed exhaust systems with slip fit pipes and U-bolt clamps and had no problem with leaks. I never used any sealer either.
    Cosmo49, 2OLD2FAST, egads and 2 others like this.
  19. bchctybob
    Joined: Sep 18, 2011
    Posts: 2,902


    If the U clamps have indented the slip joints you will need to heat them red hot to pull them apart, bummer. If you get it apart, clean the joints well. The biggest cause of leaks is not pushing the pipe all the way into the slip joint until it bottoms out before tightening the clamp. Make sure the ends are square, I even put a little bevel on the end of the pipe. One clamp per joint should do it unless they swaged the pipe way oversize.
    If you decide to weld it all up be sure you can get it out in the future if you need to. Also make sure you have access to weld all around all of the joints, sure as s#!t the part you can’t get to will leak like a bitch.

    Sent from my iPad using The H.A.M.B. mobile app
  20. Dirty Dug
    Joined: Jan 11, 2003
    Posts: 3,677

    Dirty Dug

    I put a slip joint behind the headers in the roadster in my avatar. That way the headers are removable so the starter and mufflers can be replaced without having to take the whole exhaust apart.
    egads likes this.
  21. Apache Albert
    Joined: Nov 8, 2018
    Posts: 83

    Apache Albert

    If tightening more doesn't help, they're most likely weren't assembled correctly. In terms of getting them apart, I'd start with a map gas mini torch and move up in temperature and hammer size. Then, weld everything but the headers. I try to weld everything that won't come out or restrict starters from being removed


    Sent from my SM-G960U using The H.A.M.B. mobile app
  22. fortynut
    Joined: Jul 16, 2008
    Posts: 1,038


    The quietest exhaust system I ever had came when I concluded convenience headers are just not worth the hassles. Equal length and tuned for race only, yes. So, I used cast iron exhaust manifolds, mandrel-bent tubing j's and u's, along with pieces of straight tubing and welded all of it together from the initial point where the asbestos biscuit and clamps connect to the 'down turn', all the was to the back. It was a huge pain in the ass amount of work. All I had was a portable vice, a hack-saw, vice grip clamps, disc cutter, and gas welded it a piece at the time, taking the whole caboodle loose as needed. I welded the pipes to the mufflers Used rubber-isalator type weld-on clamps --- so there was no rattle. My thinking was it wouldn't ever need maintainance just replacement.
    Cosmo49, Vic Walter and belair like this.
  23. southcross2631
    Joined: Jan 20, 2013
    Posts: 4,326


    As a former Midas muffler employee we did thousands of slip fit exhaust joints. We marked the pipe and slid the pipes together until the mark was on the edge of the joint sometimes you had to heat the pipes to get them together.
    Then we clamped the joint and then put a tack weld to make sure the pipes did not slip or twist to prevent rattles.
    I have switched to band clamps in recent years for my cars and customers cars, but still mark the pipes and put a tack weld to make sure before I install the band clamp.
    Some systems get totally welded if they can be removed easily.
    Cosmo49 and Truckdoctor Andy like this.
  24. 6sally6
    Joined: Feb 16, 2014
    Posts: 1,403


  25. JB weld around each joint, you can do that yourself...
  26. indyjps
    Joined: Feb 21, 2007
    Posts: 4,103


    If you have a mig, grind the surface and run some bead, it may not be a pretty weld - think coverage/ gap closure, not structural and be done.
    Taking it apart sounds like a horrible job that will probably not go back together well.

    Booger weld it up, or throw it away.
  27. Shawn Wildman
    Joined: Jul 8, 2018
    Posts: 33

    Shawn Wildman

    I stopped by a local muffler shop that I know has experience welding exhaust systems on classic cars. He didn't like what he saw and recommended the following:
    • Adding 3 bolt joints to the end of the headers, which I prefer. I would like to be able to easily remove the headers if needed.
    • replacing the piping with 2" piping and welding all joints.
    I would like to make the system pretty loud. I've always liked cherry bomb mufflers, so I may pull the trigger and have the whole system updated all at once.
    tb33anda3rd likes this.
  28. F-ONE
    Joined: Mar 27, 2008
    Posts: 2,533

    from Alabama

  29. F-ONE
    Joined: Mar 27, 2008
    Posts: 2,533

    from Alabama

    You did good by going to a shop. They will fix it up right. The only real reason for short sections is that's it's easier to ship.
    Having the header bolt flanges is a really good idea. It's just that headers are never easy.
    I'm goin to need a header flange added to the drivers side of my coupe. The main reason is not to remove the header but to be able to drop the pipes and service the master cylinder.
  30. 6sally6
    Joined: Feb 16, 2014
    Posts: 1,403


    Wish I could double-like this post!!!:p:p
    Brand Apart and F-ONE like this.

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