Buick 3.8/THM200 to Buick 350/TH-350 swap

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Blake442

Blake442

Geezer
Apr 24, 2007
6,774
113
Minneapolis
I'm starting this thread to show what it takes to swap from the depressing 231 Buick V6 to a proper Buick 350. :banana:
Hopefully this thread will be helpful to others who may be considering/performing this project themselves.

The basis for this project will be my 1981 Buick Century Estate Wagon that I bought in '09 with only 79K miles on it.
Unfortunately, it was overheated and spun a bearing. You should hear it knock, it's hilarious. :lol: It now has 95K on it.



These are old pics since I wasn't able to upload my new ones yet. Soon.

It's 100% complete, the cruise control even works. A/C is all there, but wasn't cold.
Not sure if I'll worry about that stuff of leave it for it's new owner... My main priority is getting it running and driving.

This is what the motor looked like before I pulled it out of my buddies '70 Skylark...


It's a, you guessed it, 1970 350 2-bbl, backed by a TH-350.
The previous owner said that he swapped to '72 heads to help with unleaded fuel, and retained the '70 intake and 2-Jet.
The TH-350 had leaked itself nearly dry, so I will be using another TH-350 that I have that I know works.

Since it had been sitting in Tucson, AZ for about 9 years without running, I took a few precautions to help my odds that the thing will run. I've gotten stuff going that had been sitting much longer, but it's always a good idea to cover your *ss.

Once the motor/trans was pulled, I separated the two and got the motor up on a stand and pulled all the accessories off.
I cleaned the motor up the best I could a.k.a. "extremely half-assed". In my defense, it was 95* out with humidity so high that the heat index was 115*, so I worked all nite since it was "cooler"... :lol:
With the layer of grunge scraped off, I pulled the spark plugs and poured a few ounces of ATF down into each cylinder before spinning it over several dozen times by hand.

Content with that, I drained the old oil and refilled it with clean oil and a new(ish) filter and removed the valve covers.
Next, I marked the positioning of the distributor and removed it to prime the oil system.
I made a brilliant priming tool using a short 15mm socket with a 3/8" washer hammered into it. I'm considering a patent.
With a 10" long 1/4" drive extension in my cordless drill, I cranked away as I watched the oil slowly come up each lifter.
Oil finally came out the last lifter just as the battery in my drill died.

I was happy with the results and reinstalled the distributor, drained the oil again and removed the oil pan to replace the gasket. Had I experienced any trouble with the oil pump earlier, I would have utilized this time to replace it. But with it seemingly working fine, I decided to let it be and just replace the pan gasket.
Inside looked good, and there wasn't any suprises laying in the bottom of the pan.

The previous owner also took the liberty of converting the distributor to HEI, so that saves me that trouble.
I have new wires and a cap, along with my choice of about a half a dozen coils to pick from laying around my garage... One is bound to work. New plugs and a rotor and I'm good there.

That's how the motor sits now, and as far as I'm concerned, it's ready to drop in.
I'll probably throw a new water pump on it as well as a fuel pump either before or after it goes in. Doesn't matter.

I'll have another buddy go thru the carb for me, and that should take care of most the the issues with the motor.

Next, I moved onto the car and started to disconnect the maze of vacuum hoses and wires, but grew tired of sweating my *ss off and called it a day.

Working nites and not having the car at my own place is killing the progress, but I have a long weekend coming up and am hoping to make some serious progress...

I'll keep updating this with new info and pictures as I can...

Any questions, comments or suggestions feel free to post.
 
Dragonist

Dragonist

Master Mechanic
Dec 3, 2010
425
16
Dallas, Tx
thanks for the write up thus far, Blake.
 
G

G-Body_Vet

Comic Book Super Hero
Oct 15, 2010
3,001
48
Good to see someone playing with a Buick 350 for once :wink:

I really don't know why this particular swap isn't more popular because it's so easy and people practically give them away. I suppose it's because the aftermarket parts aren't cheap like SBC's.

I'd love to do this swap in a 4 door Century or a 78-80 Century coupe. IIRC, the entire accessory set-up and front cover interchanges too don't they? In regards to the "new owner" comment, what are the plans for the wagon when you get done?
 
Blake442

Blake442

Geezer
Apr 24, 2007
6,774
113
Minneapolis
I already sold the wagon a few months ago as a non-runner.
Being unemployed at the time and really having no need/space for a second wagon, I unloaded it.

After discussing the options for getting it running again, we were initially going to throw another used 3.8 in it just to get the thing back on the road, but after a while we decided that the 350 was the only way to go, and I sold him my motor and trans and am now putting it together. Then it gets loaded onto a transporter and off it goes... :D
 
Blake442

Blake442

Geezer
Apr 24, 2007
6,774
113
Minneapolis
Made more progress yesterday evening getting all the wires and vacuum hoses disconnected.
Lots of stuff to fight your way through!
Also started pulling the accessories off the front of the motor.
Just need to disconnect the exhaust, remove the power steering pump, unhook the trans and motor mounts and she's ready to come out! :banana:
 
Blake442

Blake442

Geezer
Apr 24, 2007
6,774
113
Minneapolis
Got the 3.8 out of the car today. I'll try and upload my pictures in the next few days.

Everything came apart easily, but I was rather disappointed when I saw how poorly put together everything was by the fellows in Colorado that replaced the head gaskets last summer when my friend owned the car.
I can confidently say that they are 100% responsible for the failure of the V6... :roll: Dipshits...

Ordered up new motor mounts and a new transmission mount.
Next will be removing the metric 200 and slipping the TH350 in place, followed by the 350... :banana:
 
G

G-Body_Vet

Comic Book Super Hero
Oct 15, 2010
3,001
48
Looking fwd to pics myself.
 
R

rlsllc

Apprentice
Sep 24, 2007
89
0
Ohio
Awesome man! I did this same swap 20+ years ago, only it was a '79 regal, pulled a dead turbo v6 and put in a '72 350/350 from a Skylark (I think). I later put a '76 intake a quadrajet on it and HEI. It was awesome for stock. Loved it.
 
8

81cutlass

Royal Smart Person
Feb 16, 2009
1,778
113
Western MN
Cool, a buick powered buick! For some strange reason ive always wanted to take a buick wagon and stick my drawthrough motor in and put my 455 back in the cutlass, but thats a long way off.

Lookin forward to seein the finished product. 8)
 
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