GRAND PRIX 1992 LO5 TBI from roadmaster to 3.8L 84 GP

[Rehab]

hey everyone,

So new to this forum thing, don’t think I’ve ever posted on one in my life so bare with me. As the title says I’m looking to swap my TBI LO5 from my roadmaster into my 84 Grand Prix and convert it to a carb setup.
Now I have read a bunch of these forums and done a whole lot of research and I’m fairly certain I have most the issues worked out. My problem is i work overseas. I will be home for 16 days and would love to drive this with the swap complete so I’m setting my goal as done in 2 probably very long days.
A lot of these question may seem simple but I haven’t even seen the Grand Prix yet and haven’t seen my roadmaster in about 2 years so little fuzzy.
I’ll list what I know and have figured out along with any questions. Any help would be greatly appreciated.

First off not planning on getting too crazy yet. The SBC with just get a cam, intake, carb and probably headers. Easy enough and TBI gone. Also Stick with a Qjet.

- Keeping the Trans that’s in it for now as it’s less headache. Most likely a TH200 but either way same bolt pattern. So need the BOP to SBC adapter plate. Torque converter and flex plate should be fine.

- Engine / frame mounts. I assume my roadmaster engine mounts should be fine, just need a new frame mount from a
g-body that had a SB correct?

- New rad from any g-body that had the V8 from 78-87. Probably order new.

- Fan shroud. Again any G-body same years will work. Even the V6 one will do the trick for now until I have more time.

- Fuel line. Relocated from drivers side to passenger. Probably best to run new line from tank to pump?

- Trans cooler lines (to rad). Should be fine may just require some gentle adjustments.

- vacuum lines. I know there is one from the Trans to hook up, any others to mention?

- Carb linkage. Basically just make sure I get the right kit for the correct style.

- new coolant hoses. Try to find form fit, if not universal flex for now.

That’s basically what I have figured out so far. Hoping all the other accessories such as alternator and such will work without any modification.
My plan is to have all the parts waiting for me so once I’m home I can get to it. Remember it doesn’t have to be pretty as long as it’s safe enough to drive and works.
Don’t wanna be stuck in my other half’s 2002 Taurus. Not really my style lol.

Thanks for any help. If people have part numbers for anything that would be awesome.

 

[Wageslave]

Not required, but you are really going to want different heads. Swirl port heads are not good for anything high revving, and have the vertical intake bolt pattern like newer vortec heads. I would recommend either spend the money for the vertical bolt intake now, and replace the heads later with 062 vortec heads or get a decent set of used heads and intake off an older small block.

 

[Rehab]

Not required, but you are really going to want different heads. Swirl port heads are not good for anything high revving, and have the vertical intake bolt pattern like newer vortec heads. I would recommend either spend the money for the vertical bolt intake now, and replace the heads later with 062 vortec heads or get a decent set of used heads and intake off an older small block.

I have a line on a 76 lesabre 350. Would it be easier to go this route or am I just saving on the Trans adapter plate?
I feel like I’d still have to relocate fuel line, carb linkage, hoses and vacuum lines.

 

[olds307 and 403]

A Buick 350 is a near direct swap, accessories, brackets, everything. If it runs good with good oil pressure, get it, much easier.

 

[Rehab]

A Buick 350 is a near direct swap, accessories, brackets, everything. If it runs good with good oil pressure, get it, much easier.

Yeah running in the vehicle now, would have to request checking oil pressure but I’m sure he would. 70,000 miles.

I’ll have to look into what’s different here. Didn’t think I’d find a Buick so haven’t researched it. Like I said only 2 days to do the swap so need everything waiting for me.

 

[olds307 and 403]

Do a search on here, there are a couple of members on here running one. The issues with Buick V8's is wear in the aluminum oil pump front cover. If the oil pressure checks out, you are good. Just remember it is not a sbc and doesn't need 6 grand to make power. They are a light weight, torquey motor with a near equal bore and stroke. It is basically a 3.8 with 2 cylinders added.

 

[Rehab]

I am, a lot of threads to read through. This guys telling me $750 for motor, $1000 with Trans. I don’t want to change the Trans right now as I won’t have time to shorten drive shaft and such but feel it’s worth it.
Thinking just bolt the stock motor in for now. Then when time isn’t a factor I can switch build up the motor, switch Trans, gears and everything else with it.

 

[olds307 and 403]

A TH250C will last awhile behind a stock 350, if it is in good shape. Contact Mr Sony on here, he has ran a couple of Buick 350's in place of the 3.8 and has upgraded cams etc. I am a dare to be different type, anything to keep a sbc out, plus you can keep your Roadmaster in one piece and fetch parts if needed.

 

[Rehab]

Yeah I’d hate to wreck my road master for no reason. It’s damn near mint body wise. 2
Small spots of rust.
Awesome thanks a lot Olds, you’ve been a huge help.

 

[Turbolq4]

An engine swap in two days is putting in some work. Swapping to a different type of engine in that amount of time is a monumental undertaking. The Buick bolts in and is a better engine than the 305 SBC. Looks like you have a winner!

Probably should get the trans with the engine and just stuff it in a corner for when the stock one pukes.