95 Grand Prix 3800 Swap vs 3400 Top Swap

[xcdizzyx]

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.

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95 Grand Prix 3.1

[neophile_17]

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.

[xcdizzyx]

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?

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95 Grand Prix 3.1

[neophile_17]

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!

[robertisaar]

the large port heads on a small port engine doesn't change compression much, if at all. ports are a bit larger though.

[xcdizzyx]

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

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95 Grand Prix 3.1

[Guest]

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.

[xcdizzyx]

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

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95 Grand Prix 3.1

[Purple pit]

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.

[xcdizzyx]

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?

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95 Grand Prix 3.1

[Purple pit]

Very little. If you are just wanting to tune there is software out for OBD1.5.

[xcdizzyx]

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

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95 Grand Prix 3.1

[Purple pit]

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.