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Hot Rods How do you CHOP A RADIATOR ?

Discussion in 'The Hokey Ass Message Board' started by mcbay, Sep 10, 2010.

  1. mcbay
    Joined: Aug 20, 2007
    Posts: 496


    Have a 32 radiator and need to chop about 2" off for use in a Model A. What is needed to remove the lower tank and how big of a job is it to reconnect?
    Yes, I know obvious answer is a Radiator Shop.
    Any help would be most appreciated. Thanks
  2. JohnEvans
    Joined: Apr 13, 2008
    Posts: 4,883

    from Phoenix AZ

    That is a much bigger job than you might think. You have to remove and reattach the header that tubes solder into after shorting the core. If you really want to save the core go toa radiator shop !
  3. 61bone
    Joined: Feb 12, 2005
    Posts: 890


    From experience, a shop will tell you it can't be done , get a shorter core. From experience, it can be done, but is not a job to be taken lightly and it is much easier and quicker to just have a new core installed. Don't tell me it can't be done, tell me why. The cost doing it myself wasn't that much, a hundred or so to build a soldering and cleaning tank, but the satisfaction of doing it my way was immense. Would I do it again? probably not unless exactly what I wanted was not available. Incidently, the whole project took about 20 hours and only one trip to the emergency room to fix the burn.
  4. measure and buy the one you need.

    Joined: Dec 27, 2009
    Posts: 1,238


    I'd use a Hatchette ! ! (yes I am joking) !!
  6. motorhead711
    Joined: May 7, 2008
    Posts: 736


    Ya man....go to the radiator shop...I tried doing that with a radiator for my brothers car, it needed to be 3 inches shorter and we ended up ruining the's hard as hell...I'm not saying you can't do it, I'm just saying it's easier to take it to a radiator shop or have one specially ordred that is the right height or width....
  7. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,436

    Kevin Lee
    Super Moderator
    Staff Member

    I tried it once with an old radiator. The process seems really straightforward. Unsoldering everything, stripping the fins off of the core, cutting the tubes down, and re-soldering everything back together. My attempt didn't end well.

    I still think it could be done, but the last radiator I needed shortened went straight to the radiator shop. He installed a new core, relocated the fill, converted it for flathead use, and even let me chop and reweld the supports myself to keep cost down. These are the kind of guys/businesses you want to pay well to make sure they stay around.
  8. GARY?
    Joined: Aug 15, 2005
    Posts: 1,626


    I'm with the "take it to a radiator shop" crowd. Last on cost me 200 bucks for a new core installed.
    It seems pretty easy if you're set up for it.
  9. El KaMiNo KiD
    Joined: Jun 15, 2009
    Posts: 509

    El KaMiNo KiD

    x7 on taking it to a shop..i tried just repairing one and it ended bad...
  10. mcbay
    Joined: Aug 20, 2007
    Posts: 496


    Thanks for the replies. But still would like to know the procedure for removing the bottom tank.:confused:
    I think cutting it down and resizing the surround is where I will go and once all is cool take it to a R Shop and let them put it back together or re-core.
  11. Gregg Pellicer
    Joined: Aug 20, 2004
    Posts: 1,347

    Gregg Pellicer

    To take the tank off is easy. Simply heat the seam of the tank till solder melt's and tap on tank with a hammer. Dont beat on it and dont use excessive heat. You can use an air blower to blow the melted solder from the seam.You remove the header basicly the same way melt the solder and blow it off and tap header off with a hammer.Like everyone else said take it to a radiator shop . Getting it apart is easy getting it back together aint.
  12. carcrazyjohn
    Joined: Apr 16, 2008
    Posts: 4,844

    from trevose pa

    Speedway sells one already chopped .Probably cheaper than getting it recored .Did you ask your neighbor Tom yet ,He is one hell of a fabricator ,Even though The 32 isn't done.Thats my dads roadster that is in my album .
  13. Oh man, it is a big job and something you probably wouldn't do in the first year working in a radiator shop.
    Take the radiator and first you need to take off the side bands that go from top tank to bottom tank. You can just take them off just the bottom but they get in the way when still soldered to the top tank unless you have a proper radiator jig.
    Once the bands are off take the radiator and sit it on its side so the bottom of the tank and header plate are hanging off the bench.
    Begin heating the tank/header plate seam until the solder begins to melt. Use the back of the wire brush to gently tap on the tank to help the molten solder flow. Once no more solder is flowing out it pays to use the wire brush side to give the open seam a few cleaning wipes lengthwise.
    Be careful to try and keep the heat centered on the seam and do not heat the core of the radiator too much at this stage.
    Once the solder is all out either use the wire brush in the water spout to lever off the tank or a set of pliers. If it wont come off easily use a little more heat and 'wiggle' the tank until it comes off.
    Just remember its only copper and brass, BE GENTLE!
    Now you have the header plate to remove, this is the plate thats left that has all the tubes come through, use the same technique as you used on the tank to flow the solder away from the tubes. Remember too much heat will ruin the radiator!
    This will take a while, especially if its your first attempt. There is a fine line between heat/solder flow and too much heat. Use a good pair of pliers to gently work the header plate off once the solder has run out. Be careful not to bend the header plate. That will cause MAJOR headaches later.
    Once the header plate is off now you need to shorten the core. Measure, mark and cut with a course hack saw. This is pretty easy and it seems like your doing a hack job but its the easiest way to do it!
    Now here there are two ways to go depending on the type of core you have, is it an original with the cooling fins running all the way across the core or a more modern one with the little zigzag fins that sit between the tubes??
    I'm making the assumption (Right or wrong) that you have the original style. You will need to remove 3 or 4 of the fins, they are a one piece pressing but are VERY delicate and will burn through quickly with too much heat. Again gently apply heat and pull on the fins with pliers and they will come off.

    Ok, so now you have the thing apart and the right length. Its time to clean up, we used to heat up the tanks and header plates and cleaned with acid. These days OH&S make us clean them in a sand blast cabinet..........probably the best way to do it.........
    You also need to clean the tubes you have exposed, and not in the sand blaster (Hey I've seen people try!). Wire brush and some heat will do as the tubes will be already covered in solder (Tinned) you just want to clean then to bare solder.
    Now place the header plate back onto the core, it will only line up one way. You may need to gently tap it back on with a hammer. Its easier to have the radiator upside down for all this. To ensure it is on level use a small spirit level.
    You want about 5mm of the tubes to be sticking up through the header plate.
    Now you need solder and flux (I think some sticks of 50/50 is best and bakers soda flux). Start to heat the header plate at one end, again too much heat and you will ruin it. With a 1inch paintbrush run some flux across the header plate, begin melting solder around the tubes.
    This is hard to do and the apprentice usually ruins a few radiators before they learn how to do this right. Keeping the solder elastic, enough flux so it will flow and not too much heat is an art form.
    But if you have come this far, keep going until you have soldered on the header plate.
    Now the header plate is on, you need to place the tank back on. It can take a little 'massaging' of the tank and tapping with the wire brush to get it to sit on properly. This is probably the most difficult part to do now, solder the tank on. Again it is heat the seam, apply flux and melt solder into the seam to fill it. The issue here is getting things too hot and melting the solder out of the header plate while you work, this is VERY easy to do.
    Work your way around the tank, it can help to run another bead around the spout to ensure there is no leaks. Finlay solder back on the side bands, this takes a little more heat as the bands are considerably thicker and steel.
    It pays to pressure test the radiator by blocking off the spouts and blowing air in through the filler. Low pressure, you only need 10-15psi. dunk it all in a water tank and submerge. Let all the slack air bubble away then examine everywhere you have worked.
    If you see bubbles, try to run some solder into the
    If no bubbles, clean, dry, paint and install.

  14. mcbay
    Joined: Aug 20, 2007
    Posts: 496


    Hey Doc, Thanks for the details. I will take it as far as I can. Know what you mean about soldering. It is a fine art of heat and timing.
    Thanks again.
  15. DirtyJohn
    Joined: Sep 9, 2009
    Posts: 1,065


    Blowing off slag is no big whoop...watched Pop do it all day,every day for years. Takes a skilled radiator mechanic to pull this chop job off and there ain't many left. I don't think most would even want to screw with it because it is too time consuming...IF they could get it right. Header plates are notorius for leaking if the solder is not ran correctly. Have to check it under pressure as mentioned before and well...this is just a bad idea! LOL. I think you would find just pulling the tanks and putting them back on to be harder than expected. Oh well, Edison said he would never have invented the lightbulb if he knew it was impossible!
  16. Mooney
    Joined: Sep 7, 2005
    Posts: 21


    We use to use a oxy/propane torch with a rosebud type tip for radiator work. Taking it apart was easy and like the others have stated a pain to get together. It takes a ton of flux and solder to get a header to seal. The solder has to flow around the tubes and that takes a lot of heat spread around. You might as well rod out the tubes while you have the radiator apart for more flow (if a radiator this old has tubes idk). We also used special clamps and jigs to hold the radiator together while soldering. I worked at a radiator shop for a few years before I went into the Navy. Have fun!
  17. loudpedal
    Joined: Mar 23, 2004
    Posts: 2,185

    from SLC Utah

    It can be done and it's not that hard. I've done it several times. The keys are extremely clean joints prior to soldering, the correct solder and the correct flux. I got my first inspiration in 2004 from Slag Kustom. is my source for flux and solder. Here is his post from '04:

  18. Bloodandmotoroil
    Joined: Feb 22, 2010
    Posts: 154


    never cared to shorten one, just junkyarded till i found one that would work, it's lazy but it works.
  19. DirtyJohn
    Joined: Sep 9, 2009
    Posts: 1,065


    Just want to clarify that I admire the ambition to want to attempt this. Love the work ethic, but just believe that this is a nightmare in the making.
  20. brigrat
    Joined: Nov 9, 2007
    Posts: 5,360

    from Wa.St.

    Well this brings back memories, when I was younger and working in a couple NW radiator shops we used to make our own flux brushes out of horse tails. They would be cut of at the stump, hung up on the back fence till the maggots got their fill than we would cut the hair off and wire it to a stick. If you plan on doing this yourself I have a couple Tennessee Walkers out back I am tired of feeding. Your chances of chopping a new core at home isn't real good, your chances of chopping old, used, dirty core is next to nill.....................
  21. pdq67
    Joined: Feb 12, 2007
    Posts: 787


    I lost a rad in my '64 Ford/F/L 500 S/W with a 260 engine in it so I went looking for another rad.

    The shop had an acid tank as well as pressure tanks and molten soder tanks to dip the acid cleaned core tubes ends into before they did the flat top and bottom tube plate sodering back together so they could end up sodering both the top and the bottom tanks back on..

    Quite a deal to kinda be able to see this being done and fwiw, my new in the box Modine stock copper new rad was only something like $120 back then...

  22. Yeah we used the clamps and all but I didnt think they would be avaliable for a one off job in the back yard.
    My father owned 3 radiator shops when I was growing up, I worked in them from about age 12 untill I left home. We used to have the acid baths, solder baths etc. OH&S has ended all them now, tinning is all done with a stick of solder the flux brush and a torch. Cleaning is either wire brush or the blasting booth.
    I remember ending ip thrown in the test tank quite a few times, it was the size of a small pool!

    You would be much better off finding a shop that can do this for you.


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