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95 Grand Prix 3800 Swap vs 3400 Top Swap

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  • 95 Grand Prix 3800 Swap vs 3400 Top Swap

    Any thoughts or advice from someone who has taken on either? I want more power but I'm not sure I want the hassle of swapping the entire engine rather maybe just throw some better heads LIM and UIM on? I want to convert to obd 2 also any suggestions or diagrams for that? Thanks in advance for any help.

    Sent from OneTouch Fierce XL
    95 Grand Prix 3.1

  • #2
    The 3800 is a completely different motor. If you keep the 3.1L bottom end you can't use 3800 heads. This site isn't geared to the 3800 as it is a 90 degree V6 even if they share a bell housing pattern.

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    • #3
      Originally posted by neophile_17 View Post
      The 3800 is a completely different motor. If you keep the 3.1L bottom end you can't use 3800 heads. This site isn't geared to the 3800 as it is a 90 degree V6 even if they share a bell housing pattern.
      I was talking about swapping the 3400 heads and intakes not the 3800. If I was doing anything with the 3800 it would be a full swap. Are the 3400 heads direct bolt on to the 3100 block?

      Sent from OneTouch Fierce XL
      95 Grand Prix 3.1

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      • #4
        Sorry I took not sure you want to pull the motor as you don't want to pull the motor. Probably read too quickly. The heads bolt up but I don't recall what you end up with for a compression ratio. Good luck!

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        • #5
          the large port heads on a small port engine doesn't change compression much, if at all. ports are a bit larger though.
          1995 Monte Carlo LS 3100, 4T60E...for now, future plans include driving it until the wheels fall off!
          Latest nAst1 files here!
          Need a wiring diagram for any GM car or truck from 82-06(and 07-08 cars)? PM me!

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          • #6
            So would it be worth it to swap the 3400 heads LIM and UIM or just the intakes or what about the 3500 top swap? I really just want more power without swapping to a 3800

            Sent from OneTouch Fierce XL
            95 Grand Prix 3.1
            Last edited by xcdizzyx; 01-12-2016, 02:57 AM.

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            • #7
              3400 heads on a 3100 bottom end will end up with the same SCR, 9.5:1. Combustion chambers are the same size between the 3100 and 3400 (and 2.8 and 3.1).

              The 3500 heads can't be used on a 3100 block due to the smaller bore. Th e3.4/3400 block is the smallest bore recommended for the 3500 heads, due to the much larger combustion chamber of the 3500 heads.

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              • #8
                So really my only option is the 3400 intakes what about the throttle body is there any difference? Also I really want to convert to obd2 how much of a headache am I looking at

                Sent from OneTouch Fierce XL
                95 Grand Prix 3.1

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                • #9
                  Big port 3100 or 3400 TB's are a bit bigger than what you have. That said they have the same shape before the butterfly and are not the best for flow. A straight wall TB is much better. If you don't care about that they work just fine. Just remember to swap your small port TB shaft into the 3100/3400 TB so you can keep your throttle linkage. If you have a new TPS and IAC they can be put on the big 3100 or 3400 TB.
                  95 Beretta 3100 with 3400 intakes and TCE TB
                  High flow cat and a Magnaflow muffler
                  Grand Prix trans with 3.33FDR

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                  • #10
                    Originally posted by Purple pit View Post
                    Big port 3100 or 3400 TB's are a bit bigger than what you have. That said they have the same shape before the butterfly and are not the best for flow. A straight wall TB is much better. If you don't care about that they work just fine. Just remember to swap your small port TB shaft into the 3100/3400 TB so you can keep your throttle linkage. If you have a new TPS and IAC they can be put on the big 3100 or 3400 TB.
                    OK thanks. Do you know anything about switching to obd2?

                    Sent from OneTouch Fierce XL
                    95 Grand Prix 3.1

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                    • #11
                      Very little. If you are just wanting to tune there is software out for OBD1.5.
                      95 Beretta 3100 with 3400 intakes and TCE TB
                      High flow cat and a Magnaflow muffler
                      Grand Prix trans with 3.33FDR

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                      • #12
                        Originally posted by Purple pit View Post
                        Very little. If you are just wanting to tune there is software out for OBD1.5.
                        Is there a certain software and adapter setup you'd recommend. I know nothing of tuning but it's something interested in doing

                        Sent from OneTouch Fierce XL
                        95 Grand Prix 3.1

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                        • #13
                          Tuner CATS and DHP(I think). Have not really looked into it. You can dig around here for better info or there is a web search. Can tell you there is nothing good that is cheap.

                          My car is still unturned, does fine, but it would help.
                          95 Beretta 3100 with 3400 intakes and TCE TB
                          High flow cat and a Magnaflow muffler
                          Grand Prix trans with 3.33FDR

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