chassis welding advice

  1. elobire New Member

    UK, wales
    Hi guys,
    I bought a '89 Toyota MR2 a few months back that had been sitting and found that it has quite a lot of rust, the worst of which is on the front chasis rails right where the control arm mounts.
    My experience in welding is quite limited, I had a cheap gassless mig years ago that I did a little bit with and have since bought a Wolf 140 that I havnt used a whole lot yet. I'm in no rush to get this done though, so if it takes a few months of learning first then I'm fine with that.

    I've managed to find a breaker that has what looks like a decent condition chasis he will cut the front section off for me, but I need advice on what the best way to weld this to my existing frame would be.
    I have read varying posts on the internet about cutting the box section sort of like a step so that there is more surface area in the weld as well as slipping a smaller peice of box section inside the chasis to back it for additional strength. What do you guys think of this?
    Any advice would be great :p
    Here are some pictures:


    The drivers side is not as bad but still not good. I'm unsure if I should just replace tho whole thing on this side, or maybe just try and replace the bottom half of the rail where the rust is?


    Heres a reference for where the rust is on the car. the rust goes for about 5" after that hole you can see here.
  2. Morrisman

    Morrisman Forum Supporter

    Does the MR2 actually have a chassis, or is it monocoque? If you go chopping great pieces off you may need some sort of chassis jig to make sure it is all assembled square and straight and your suspension mounting points are aligned.
  3. elobire New Member

    UK, wales
    It is monocoque. Keeping it square is one of the worries I have about doing this and I was thinking about making up a little jig to make sure it goes in the right place. For the control arm mounting points, theres another two holes that you can see on the top right of the first picture that I wont be removing as the metal there is decent, so I was hoping I could use those to make sure the new chassis/ other mount point is in the right spot.
  4. Dcal Member

    Antrim Northern Ireland
    No need to worry about beefing up the rusted out area with extra box and the like, just try and get it back to the condition it was in when it left the factory.

    The chassis leg will have plenty of strength in it.
    It would have folded in two with that amount of rust damage if it didn't.

    I think there are two approaches you could take -
    First is just remove as little metal and replace it a but at a time while allowing the remaining metal to support the shell while you are carrying out the repair or -
    Cut the whole lot out in one go and replace that.

    It will depend on how bad it is.
    If the latter

    Get as much of the repair section as you can from the scrappy and plan to cut back to a place where it is easy to weld and if possible not under much stress.
    Over lapping the repair is a good idea
    It would also be good if you were able to pick up a lot of the spot welds in to the floor and inner guard, I will make lining it all up a lot easier and make the repair stronger and with less reliance on a single butt weld.

    As @Morrisman says before you start cutting any metal, check that everything is square and take lots of measurements.
    Better still (while still taking lots of measurements) fabricate braces from some steel angle / box and weld / bolt it in place to pick up and triangulate the suspension mounting points so you can lock everything in place and stiffen the shell while you cut lumps of it out.
    If its already twisted, straighten it first and make sure you don't lock in any distortion

    Good luck and don't be afraid to ask plenty of questions / post photos before you start the grinder up.
    Morrisman likes this.
  5. Morrisman

    Morrisman Forum Supporter

    You could build a basic tubular frame that spans several mounting points, and important holes bolt to, so when you hack the rotted part off you can locate the new piece precisely. It needn’t be a thing of beauty, as long as it is solid and won’t flex at all.
    slim_boy_fat and Dcal like this.
  6. elobire New Member

    UK, wales
    Thanks guys I will definetly make up some kind of frame. I think I will probably go with replacing the passengers side and patching up the drivers side, but I will see how things go once I start cutting into it and get a better view.
    I'll definetly be back with more questions and photos once I start.
  7. Justme

    Justme Member

    Pwllheli Wales
    If the other one is good why not fix that one up?
  8. arther dailey Member

    Southampton England
    you might also get your hand in first on some scrap, especially if you have to weld laying down, some practice is usefull to get the settings right. enjoy.