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3100 to 3400 or 2000+ 3100 intake swap.

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  • 3100 to 3400 or 2000+ 3100 intake swap.

    I got a 98 GA with the 3100 v6 and i have been looking around several sites like Wot tech reading about the swap, all i want to do is the lower and upper intake from the large port 3400 or the 2000 + 3100 plenum. Could i use a gasket kit designed for the newer 3100(lg or 3400 , or will i need to buy some sort of hybrid gasket set like the one Wot-Tech sells that they say is made to fit the 3100 head cuz they have some sort of pin to align the gasket that its not in the newer lim. About the heater core tube, i saw a thread were someone mentioned that the lim off a 96-98 3400 that is used in minivans will have the threaded insert so my stock 3100 tube will fit, instead of getting the whole tube replaced with the press in one.

    Is there anything else about this swap that i have to worry about, i already know i gotta remove the pushrods to be able to put the new gasket in but that i will do with those rocker arm compress tools that are around.

  • #2
    I always just used a large port gasket set for a 3400... I never swapped heads either I was using 3100 ones to my knowledge... I used a press in LIM but i got the tap and threaded it to the right size, If you find one that is threaded, yes that will save you some time and headache...

    As far as the push-rods go, just take the rockers off and remove them, you will also have to grind down the bottom of the LIM to clear the stamped steel rockers, unless you plan on swapping to roller rockers from a 3400. I'm not sure if the 98GA's came with the rollers or not, the heads may have the notches for them if you get a set though... I know some 96 engines had the provisions for them but they just weren't used.

    Alignment pin that is spoken of may be the one that's right above the center port in on the heads... I'm not sure but I thought that was there on all the heads.

    There are quite a few threads on how this is done already.

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    • #3
      All engines after 96 received roller rockers, so that will not be an issue.
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      • #4

        Here is an excellent and comprehensive textual and photo-play walk-through on doing the LIM and Head Gasket Replacement on the GM 3400 Engines:


        • #5
          98 grand swap.

          Your 98 grand am is the same set up that was in my 96 gagt. I would use manifolds from the 2000+ era. You can find a lower intake manifold with the "threaded" fitting from a late 90's minivan, but that may be tough. Either get the manifolds from a vehicle that that still has the slip in pipe. Retain the pipe and modify your hose to connect to the pipe or thread the lower manifold with the correct size NPT tap (what I did) and proceed as usually. You will need the egr to manifold pipe and egr, if your manifold doesn't come with the valve on it. I happened to get my parts from a 2000 malibu. It had the big port "3100" upper and I like that look. If you're contemplating swapping heads, you might as well do it now. When I first swapped the manifolds, I didn't swap heads. I gasket matched the heads to the gasket I used to correct the horrible misalignment between the lower intake and the heads. It ran great until those plastic intake manifold gaskets took a dump again. Now that I have to go in again, the heads are coming off for the "newer" versions. Just do it once and forget about it.....


          • #6
            So my l82 heads dont match with the lg8 lim gaskets ? Also when i get to it im gonna buy metal gaskets not the plastic ones.


            • #7
              if leaving your stock heads, you going to use the gasket that matches the lower intake that you're using. whatever gasket you use, it better be the metal type or you'll be back in there around 20-30k miles from now. the ports on the "newer" style intakes lowers are slight different that the older style ones. when you have the intake off, have the new gasket available to lay on top of the head and you'll see that the shape is a bit different. I feel if you're in this deep and money allows it, swap the heads too. Since the heads have been revised and the output is higher on the later 3100's you might as well go the whole route. IF $$$ allows.......


              • #8
                No i still havent begin doing this swap and since im jobless atm money is kinda of a problem, but i have given some thoughts about it and im thinking im just gonna let the motor as it is, if by any chance my stock gaskets fail in the future and the car is worth saving i will just go to a junkyard pull the lim and uim along with a 3.4 TB and do the swap while im on that whole mess, and yes if i have to do it , ill get metal gaskets, men why the hell did GM made such a mistake with these engines regarding the intake gaskets , they should have changed the gaskets type as soon as the first leaking gasket issues appeared.

                Anyways thanks for the replys guys.