Engine Swap Q's For You GM Guys

[I Like Waffle]

So ive got a 1981 pontiac with a 3.8 v6 in it. Original motor was a 350 but that shit the bucket and my grandfather had this put in it for some reason. The ***** i believe is a 700r4, its a 6 speed ***** is really all i know. I have a 76 chevy C10 with a good running 350 in it, would there be any issues with swapping the 2 and having it bolt up to the *****? Ive got yes and no from different people on this issue, im thinking maybe i should just find another 3.8 and put it in there. The one i have has a rear main leak i havent repaired and its starting to knock too it seems, only around the 2k rpm range though. Also has 2 stuck valves on the last cylinder on the left, so that cylinder doesnt do shit. lol //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

Another thing im wondering is this engine has the computer controlled carb shit, MAP sensors and all that mess. What kind of electrical wiring issues will i have?

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[whitedragon551 5,000+ posts]

You will have a hard time and alot of money to go back to a 350. Id try to get a 3.8 V6 Series III with the supercharger on it and just work from there. If the 3.8 hooks up without any other mods the 3.8 SC engine should to. They are the same except from the SC.

The 3.8 V6 come in the Grand Prixs, Montes, and Regals. A good place to check would be clubgp.com

Its a national Grand Prix club and alot of people on there know what they are doing.

 

[Varinabassing 10+ year member]

Do you know if this had a lt package or not? If he some how got a v6 in there after having a 350 it prolly had fab work done to get the motor mounts in there. Going back to a 350 wouldnt be tooo hard but you will have a decent amount of issues wit it mounting up. You will have to move the mounts back to their orignal spot I never played wit electrical carbs but i would scrap that and just run a decent carb I guess i never gave you a yes or no because yes you can get it in there but no its not going to bolt right up. I dont think a 700r4 will bolt to a 3.8 but i know it will bolt to a 350 So i not sure it that really is a 700r4 My advice is if your not confident dont do it maybe pay someone to do it You will need a welder that i am sure of Good luck buddy

 

[06goat 10+ year member]

Id just get a 3.8

Those motors are bulletproof. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[SicAudio 5,000+ posts]

just fix the 3.8 you have it is cheaper and easier, then get an intake and supercharger and bolt it up.

 

[whitedragon551 5,000+ posts]

A top swap on the series II V6 is about $1200 for parts. While your in there you might as well do a cam, valves, springs, pushrods, pistons, and to top it off you will need a tune bad. Will cost you almost $2000 plus labor. You can get a used 3.8 V6 SC for $800 used.

 

[I Like Waffle]

Yea my 3.8 has been good to me for the most part. Its got about 500k on the clock so i figure its seen its days. This was actually the original engine (my grandma told me that he had the motor changed) but the vin says differently. I assume he most likely had the ***** replaced and she just didnt know better.

But anyway, wouldnt it be a ***** to swap in an EFI + SC'ed 3.8 with all the wiring and such? Mine just has a regular 2 barrel carb for the most part. Has a computer controlled TPS and some other crap that i dont know much about. I may just swap another 3.8 like you guys said, but if it isnt too bad to add the supercharger and such then ill go for that too. But im not gonna spend 2-3k on this car if thats what your getting at.

 

[1980supreme 10+ year member]

a non-turbo 3.8 isn't worth putting any money into. The supercharged versions of this motor are out of newer, computer controlled front wheel drive cars, and will not work.

I highly recommend a 350. Due to emission regulations and fuel scares back then, they made the 3.8's HUGE slugs(which is why they last forever).

700r4's are 4 speeds, which is what the car most likely had from the factory unless it was a 5 speed. they're basically a non computer 4l60e. they came in a few cars. mostly the minitrucks, half ton (1500 series) chevy's, firebirds and camaros.

BOP (buick olds pontiac) transmissions have a different bellhousing bolt pattern than the chevy and the 3.8 will have different motor mounts than a 350.

I don't know anything about the 6 speeds in those cars, But i do know that they only came in newer years. (yours did not come factory with a 6 speed)

it's quite an easy swap once you've figured out what you're starting with.

If it's a BOP transmission, get a BOP motor and the stock BOP V8 mounts and you're good to go.

If it's a chevy transmission, its your trucks motor and find some chevy V8 motor mounts.

i'm assuming this is either a firebird or a grand prix. If it's a grand prix most likely came with a th350 (transmission) from the factory.