3.9 to 3.5 Swap/Fitment - Pontiac G6 Forum
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post #1 of 2 (permalink) Old 03-05-2019, 03:30 PM Thread Starter
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3.9 to 3.5 Swap/Fitment

Hello all! New to the forum because plenty of research hasnt exactly answered my questions to the level of comfort I am needing. I picked up a 2006 gtp with the 3.9. The car is from a family friend and pretty clean which is why I got it knowing the issues. The motor runs, but has a knock. I noticed a coolant leak so figured the motor got hot and blew a ring or something similar. The body only has 130k, so i was thinking simple motor replacement. I have come to find out the 3.9 is a more difficult motor to scavenge than the lesser 3.5 counterpart. I was curious in doing a 3.5 swap, as the more performance isn't a factor to me (currently I daily a 440whp truck, and I want more economy). If the 3.5 wasnt a good option, would the 3.9 out of the impalas work as well? Im new to the front wheel drive scene, so I'm unsure of this versatility. I did the 4.3 to 5.3 swap on my sierra, so I would like to say im mechanically inclined. Just looking for some advice to close the gap!
Thanks in advance!
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post #2 of 2 (permalink) Old 03-16-2019, 08:46 AM
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Swapping the 3.9 for another 3.9 is the most straight forward of any swap. Swapping in a 3.5 would require the ECM & BCM of the donor vehicle & a reprogram. With the 3.9 all you need is the motor from the donor car.

I did the swap in my '06 GTP. Pulled the motor out of a Montana SV6. Bought just the long block as it was cheaper ($150 vs $500) and a new gasket set. Had the whole thing done in a weekend.

Aside from the G6, look at Chevy Malibu, Impala, Uplander, Monte Carlo, Buick Terraza, Lucerne, Pontiac Montana SV6, and Saturn Relay
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