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Good Morning, all.
I’m Zach from Montana.
Last year, I lucked out and got my hands on a 1971 Cutlass "S" that I've been slowly tinkering away with as the weather allows. She's ugly as sin right now, but she'll get there.
I've found a lot of helpful information on this forum while doing my due diligence and figured I should actually join up and have some conversations. First restoration project, first full engine overhaul, first lots of things... I've always been able to figure things out, and I've got all of the CSMs, factory assembly manuals, electrical diagrams, etc, but sometimes hearing from experience or "If I had to do it again" stories can solve the mystery.
The car is pretty much like it was when it left the factory, and aside from the layers of goop, sludge and dirt, appears in pretty good shape. Stock 350 / THM350, factory A/C, factory 2bbl.
It ran just fine before I tore the front-end apart and disassembled the engine. Stock everything, so a pretty good platform to take it where I want it, I think.
Along with the car, I received a 1968 455 that is rebuildable, and what I think is a 1967 TH400 a 1967 Buick "Super Turbine 400" TH400 with switch pitch. I'm torn between doing the 350 to 455 swap, or keeping this "S" all numbers-matching original and saving the 455 for another project if I can get my hands on another BOP A-body later on. Time will tell, or if I manage to blow up the 350- Hey, got a back up big block...
Goal is a solid, reliable street car with some attitude, nothing too crazy. (I tell myself that now...)
Looking forward to learning from you all and keeping another Olds on the road.
Cheers.
Last edited by ZSmith74; Nov 11, 2025 at 07:37 AM.
Welcome. The 350 can easily make over 400 HP and TQ, roller cam, aluminum heads and better pistons with headers and duals. Also the stroker route for about 100 HP/TQ more. The 455 can make even more power. What heads and what year is the 455 supposed to be?
You state that you have an extra 68 455. The most horsepower and torque per dollar spent on a rebuild will come via the 455. I like the low-end torque developed by the 455 for street cars.
What heads and what year is the 455 supposed to be?
The 455 codes out to a 1968 out of Southgate, but had '71 G heads installed on it. I haven't taken it much further apart than that until I make some more room.
Originally Posted by Tri-Carb
You state that you have an extra 68 455. The most horsepower and torque per dollar spent on a rebuild will come via the 455. I like the low-end torque developed by the 455 for street cars.
I don't disagree, and that motor keeps looking at me like the Green Goblin mask. I'm going to drop the 350 off at the machine shop within the next couple of days for cleaning and inspection, I should crack the big block open and take a look at things. I've got the time and resources to fix them both back up.
Welcome, the 67 T400 may be a switch pitch and would require a special converter and activation switch and wiring.
Good call, thanks for that! I cleaned the tag off, looks like a 67 Buick "Super Turbine" flavored th400 and has the wired solenoid for the switch pitch.
Learning new things on day one, right on.
Being "just" a Cutlass S and not a W machine or other notable high value car, going with the 455 isn't going to be a big hit on the car's value. And if you want to play it safe, hang onto the 350. The 350 can be plenty of fun, but the 455 is even more funner if you don't mind the gas bill!
Being "just" a Cutlass S and not a W machine or other notable high value car, going with the 455 isn't going to be a big hit on the car's value. And if you want to play it safe, hang onto the 350. The 350 can be plenty of fun, but the 455 is even more funner if you don't mind the gas bill!
Originally Posted by Greg Rogers
Welcome, I would go for the 455 if it is a good builder- similar $'s cost to rebuild either so go for the big one!! Keep us informed!!
Originally Posted by JohnnyBs68S
Cool project, welcome. Keep in mind that switching from a SBO to BBO will also require the front springs to be swapped to maintain ride height.
Originally Posted by Minibike Mark
Welcome!
I'd go with the 455, no replacement for displacement. Being a '68 you might get lucky and have a forged crankshaft.
Originally Posted by Rallye469
I’m in the 455 camp.
More HP per $ = more fun
Cool car. My first olds was a ‘70 S post coupe.
Well you've had me thinking about it and convinced me. I was holding off due to the extra considerations I'd need for the swap, but I've already hit the point of no return so might as well...
"Well why not drop the tranny and have it rebuilt? Why not replace the front end suspension while the fenders are off? Why not bust rust and paint the front frame? Wait, I know a powder coat guy, Why not take the whole body off and restore the frame??"
Think I'll spend today getting it up on a stand and checking internals, then let the machine shop tell me if they think they can save it.
Thanks, folks. 😁
C heads are fairly common. If you see some locally, you may get a good deal. Increasing costs make shipping heads somewhat impractical.
I've looked around for sure. Found a couple of pairs through the Bay, but yes, the shipping costs added onto asking price makes hitting any kind of "purchase button" a questionable moment.
Every local scrapyard around here doesn't have any Oldsmobile anything laying around anymore. It was kind of heartbreaking, BUT there is a place up near Kalispell that deals a lot in the classics. Going to get up there one weekend and see what I can load a trailer with.
