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Cast aluminum intake repair and modification

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  • Cast aluminum intake repair and modification

    Two things I'd like to accomplish on a cast aluminum intake. This is the bottom half of a two-piece intake that I'm working with. The first task is to repair a bolt hole by filling the damaged hole, drilling and tapping. The second task is to remove and block an EGR passage from the intake.

    The red arrow points to the damaged bolt hole:
    Click image for larger version

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    The EGR passage is circled in red:
    Click image for larger version

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    For the bolt hole, I've seen suggestions to cut a piece of 4043 aluminum round rod, drop it in the hole and TIG weld it in. I have not been able to find 4043 aluminum round rod, any suggestions or alternatives? Also, will I need to have the adjacent flange milled flat after the welding is complete?

    For the EGR passage, I plan to remove the passage with a cut off wheel, angle grinder and carbide rotary burr. This will leave an opening in the floor of the intake that is about 1.5" square. The floor of the intake will need TIG welded closed after the passage is removed. Here is the procedure I've come up with from reading the forums:
    -Clean the intake manifold very well.
    -Grind away surface aluminum where possible (so that new, clean aluminum is exposed).
    -Preheat the manifold to 300 degrees (to clean it further).
    -Cut some pieces of 4043 aluminum to fill in the hole.
    -Use 4043 filler rod.
    -Use a pure tungsten electrode.
    -Argon shielding gas...?

    Does this sound right?

    Is it likely that the sealing surfaces of the intake will need to be milled flat after the welding is complete?

    I appreciate any advice.

    Paul Lohr

  • #2
    Why not put a threaded insert into the hole? If you put a round rod in and weld, the weld will only be at the top and not very strong as I see it.
    Why are you removing the passage?. Why not just block it?
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    • #3
      As far as the stripped hole is concerned, you really want to use a commercial thread repair product. Heli-coils are simple and readily available, but there are a whole bunch of alternatives. I have heard good things about time-certs.

      In the Porsche tuning community it is not uncommon to put thread inserts in perfectly good threaded holes. The reasoning is that the thread repair/replacement will bear on a greater surface area of the aluminum and the contact area with the bolt will be steel or other harder material. I've done a few heli-coils in my 914, 914s are notorious for pulling out exhaust studs, and I haven't had a heli-coil pull out yet. Some of them have been in there for 10 years or more.

      As far as the EGR port, if this is a high-performance application, there will be a community that can tell you what the best approach is. For a normal application I'd be really surprised that the flow improvement in the manifold would be noticable. If you decide to cut it, and you decide that 4043 is the ideal material to fill the hole, you can probably get a small piece from an online metals store. Just use your favorite search engine.


      • #4
        When i do stripped holes i drill them bigger then fill with weld. That way when you redrill and retap you are in a clean hole with no old threads...Bob
        Bob Wright


        • #5
          For me eze-lpk thread insert on the bolt hole.


          • #6
            Thanks, everyone for helping with these questions.

            monte55, Kevin, and Sberry:
            The hole has been drilled too large for a wire-type thread insert (such as Heli-coil). Yes, I can get a keensert or timesert oversized threaded bushing but we are talking about $80 to fix one bolt hole by the time I get the specialized tools. If the mating surface had to be re-machined after welding the bolt hole closed, I think I would be in for a good bit more than $80.

            I will check into the eze-lpk threaded inserts.

            I see your point about the aluminum rod only being welded at the top of the bolt hole. I could cut the round aluminum rod into several pieces and weld it in stages. Would this be better? I still don't know what type of aluminum to buy or if the flange will need to be re-machined.

            The EGR passage blocks 80% of the width of the cylinder #1 intake port. The passage somewhat blocks the intake ports for cylinders 2 and 4. I think it really needs to be removed. I'd like to know what type of aluminum should be used to build the pieces that will be welded in. I can keep the intake bolted to the engine while welding - perhaps that will keep warpage minimized?

            Thanks again for your help,
            Paul Lohr


            • #7
              Is this intake used on a turbocharged or supercharged engine? If so then I would recommend that the intake flange be machined down flush where you do the welding/repair work. If it is on a naturaly asperated engine then just carefully grinding the area down flush should be fine.
              But on that note, I personaly would not recommend trying to fill the hole with material and welding it, especialy not in pieces/layers, doing that may cause problems with drilling and tapping through the material since the only welded part of each piece would be the top side, the bottom would be unwelded.
              I'd use one solid piece of material that you simply grind down to fit and make the hole as big as you are comfortable making it, obviously leaving a decent sized edge on the inside edge of the bolt hole, then put the piece in making sure to make it short enough to be a 1/8"-1/4" too short at a minimum, more space then that would be even better, so you have that 1/8-1/4 or more space at the top after putting the piece all the way in the hole so you can fill that space in completely when you weld it, also I would make sure to bevel the top edge of the material piece you are using to fill most of the hole so you can get better penetration around the edges of the piece.

              As for the egr port, i think just filling it in whatever manner you choose would be fine

              sorry for the long post
              Last edited by Ford1989; 11-04-2011, 05:10 AM.


              • #8
                i have had alot of luck with 5356 rod on cast alum repairs myself. it really depends on the casting... your local steel supplier should have some stock on alum plate. keep in mind most plate stock is 5052 because 6061 does not form well. as for the bolt hole clean with a solvent and preheat to try to burn out any crap left in there. weld up in stages, would also use a gas lens with a large stick out to get to the bottom of the hole.
                Last edited by arc; 11-04-2011, 09:19 AM.
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                • #9
                  With Cast Aluminum intake repairs, I've had the best luck taking the manifold off and having it cleaned in a chemical bath for aluminum materials, then having it baked before even attempting to weld.

                  Then, preheating the casting before attempting to weld but also using 5356 filler.

                  The bolt hole I would suggest just building up a puddle of material from the bottom up. The EGR port, you would probably be best just to fab a plate to cover and then weld it in. Access to the bottom may be a bit of a problem.

                  In the field, we've used a patching compound made by Lab Metal for small filling and cosmetic repairs. I use caution with any product being used that could have pieces drop out internally but Lab Metall sets up like aluminum and blends so well that it can be drilled and tapped like the casting.


                  • #10
                    460 truck intake...

                    Is this a 460 truck intake? Looks to be. Anyhow an easy way to repair, and the way I repair once a helicoil has failed, or when someone tried to repair it is to use threaded rod. Tap the hole to what ever is the next size, take a piece of threaded rod insert into tap hole, cut off flush, drill- retap, or tap before inserting, just leave a little extra rod so you can turn it into the intake, then cut off. Put a little jb weld or loctite on the rod before insertion.
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                    • #11
                      Guys, thank you very much...I am grateful for all of this help.

                      The intake manifold is from a 1986 Buick 3.8 turbo motor.

                      Ez-lok thread inserts as someone suggested will probably do the trick. There are many threaded inserts available - this one seems to be cheap and easily available. I would rather fill the hole with aluminum using the TIG welder but I am concerned about warping the flange. So I will use the threaded insert.

                      I was not clear about the EGR passage. It is actually a riser that protrudes into the intake manifold. This riser partially blocks two of the intake ports and the EGR system is not needed so I'd like to remove it. I am going to grind the passage down so it is flush with the floor and side of the intake. This will leave a 1.5" square opening in the bottom of the intake. The plan is to cut a piece of aluminum to fir the opening and weld it in. My concern was warping the flanges. I know this is a difficult question because it is hard to picture all of this.

                      Thank you for your help,
                      Paul Lohr