Need help FAST.... Helped my lil bro,who isn't a mechanic, pickup a car in Wilkes Barre, PA and it took us a lil over 3hrs to get there, as we came from Clarion, PA. Mostly all highway going East on I 80... The details of the deal were whatever, but we/he got screwed and needless to say, it made it no more than 40 miles before it overheated.. Got to the Econolodge nearby and have been there 2.5 days trying to diagnose it... Of course there's the air purge from the coolant system issue notorious of these POS 3.1's.. So after some rigging up a purge valve between the heater core hoses and eliminating it, we had a purge point higher than the factory purge points and the overall system... Finally got it figured out.. not just blown, but absolutely DESTROYED head gasket...I've never seen one so bad... The coolant was actually running out of the exhaust... Sure, misfire on Cyl #2, but can you believe it still ran?

So, my question is:: Let's say I have a 97 Chevy, Olds, Buick, or Pontiac 3800 series II motor, tranny and PCM:
What else is required as far as modifications to the subframe for mounting? There's a member by the name of nighthawke something or other who had a decent post, but I needed more info .PLEASE, ANY HELP IS APPRECIATED....

 

The 3100 really is not that bad of an engine, nor the 3400. There biggest Achilles heal is plastic intake gaskets. GM kept tweaking the platform to improve it, the block and basic design replaced the 3800 (the block is used for the 3500, I also believe 3600 and 3900).

Anycase, with a blown head gasket, that motor can run. I had one in a 94 Grand Am that it would force compression gases into the cooling system (that is probably the real reason you had an air pocket in the system to bleed out). When it sat and cooled down, a little coolant dumped into a cylinder or two. Once it blew that little bit out, car ran great. It gave a false over heat (which again, might be what happened with you guys). What I mean by false, temp rises, an air pocket sits right at the temp sensor and the air pocket does wacky things with the temp sensor. You need the t-stat to open and get the coolant moving properly and after that, temp drops to normal. I actually pulled over a couple times, left the car running and released the bleed screw on top of the coolant pipe over the water pump housing and then the t-stat opened and back in business. Don't get me wrong, if the coolant system was filled to the correct level, the pressure forced it out the radiator cap.

As for a swap, I know that 5th gen Monte did offer a 3800 Series II (Non-SuperCharged). I know there are one or two guys here who have done the swap and can talk about it. If GM did it in 97, odds are all the goodies you need are at the salvage yard.

 

Thanks for the reply. You could quite possibly be correct in that it was compression gasses which caused the flow lock. At any rate, the vehicle is currently 2 and a half hrs away and we're trying to determine what to do. It's in grade A shape as far as rust, which is bizarre in itself for PA, and there doesn't seem to be parts on it not original to the vehicle, AKA different painted back sides of panels, paint marker markings, etc... Any rust is very limited to surface and could EASILY all be taken apart, cleaned up and painted with some high $$ undercoating. So I'd hate to just take the hit, leave it rot out east and not do anything about it... I feel it's worth, even with a 3.1 replacement, to do a swap... I don't feel like taking all the time to determine how much damage had been done to this particular motor, and simply throw in a 3800 motor, tranny and PCM from a car that runs great buy won't pass PA inspection because of rust... My problem is having a game plan in place before I make a move so that I maximize my time being spent on it while having a vehicle doing nothing more than taking up space in an already crammed yard... I've done the head gaskets before on the 3.1, which I agree, really isn't that bad of a motor. Thay job is not fun, and is just as much work dropping a new unit altogether in it...

 

If it were my car I would just do a 3.1 motor swap. Engines are fairly cheap used and it would take a little over a day to complete the swap. Trying to convert to a 3.8 isn't super difficult but will take a lot more time plus the expense of additional parts and a wiring clusterf$$k of your not experienced. Good luck

 

You will likely need both of the axles, and might need to custom build your own axles from the old 3.1 setup and the new 3.8 setup. The engine and transmission should drop right in place, as long as it's an engine from the W platform (Regal, Grand Prix, Monte, I'm sure there are others). I've heard Bonneville engines need mods to the oil pan?

Anyway. The main issue may be wiring, and it may be easier to get a wiring harness from a 98-99 Monte Z34/Lumina LTZ.

 

If you are dead set on pulling this engine and don't care what damage was or was not done.... There is another upgrade option. Don't swap a 3800, swap a 3400. In the old 3100 Grand Am days, that was the upgrade to do. You can use the same engine mounting, most the same wiring and sensors, possibly some PCM tweaks and on the road with an engine that has more power than the 3100.

I posted a PDF guide that I got YEARS ago from the Grand Am community. It shares a ton of helpful info (obviously each vehicle will have it's own combination of issues to explore). Here's the link where I posted that:
https://montecarloforum.com/forum/fw...highlight=3400

Granted, the 3400 will share a lot of the same problems as the 3100, but if you are swapping it, fix them all on an engine stand before dropping it into the car.
Food for thought.

 

Besides the axles (compete) you will need z34 or a 3800 lumina wiring harness and the pcm . The axles on the 3.1 are to thin for the inner part of the inner cv joint to fit , also it may need to be reprogrammed for the security system , doing that at the moment . In my case I got a 2000 regul GS and had to rebuild trans but it was running for 300$ 👍Good luck !!