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Over my six decades I have owned four Oldsmobiles - my first car in high school was a 1970 Cutlass and I lost my virginity in the backseat. (Memories.....)
My current Olds is a 1972 Cutlass Supreme Convertible with the original 350 engine and AT. It is not a genuine 4-4-2 but is a 'Tribute' w/ trim & graphics. It has been pampered throughout its 50-year life and starts/drives wonderfully. However I find myself researching options to improve HP/torque and wanted to solicit input/feedback from this forum as I'm certain many of you have gone down this path.
Should I stick w/ the original 350 engine and have it rebuilt to increase the HP to 375-400 range; which would be a nice improvement in performance. Or should I go 'whole hog' and swap the 350 with a 455 (and a new transmission)? Is the extra 100-150HP of the 455 worth the extra cost to put a bigger smile on my face each time I drive it? Maybe.....what are YOUR thoughts?
I don't plan on ever selling the car, so I am more focused on the current driving experience than future resale value. The car will eventually be handed down to my kids in a decade or so....but until then I want to enjoy the car as a weekend cruiser to car shows, etc. It will not be raced or tracked.
Getting 375-400 horsepower out of the 350 will cost some money and most likely impact drivability, whereas a 455 at the same power levels will be just as sedate as your current engine.
My quick impression would be that you might be able to come across a solid, rebuilt big block like a couple that have been for sale here on CO recently, though by the time you deal with heads, exhaust, intake, etc you’ll be in for a chunk of money but it will be well spent.
The other fairly easy option, likely to be roughly similar expense wise, might be one of Mark’s (Cutlassefi) small block stroker kits. Will raise your 350 into big block displacement, torque and horsepower range. It’s a really well thought out package of quality components, reasonably priced. You can buy the kit if you have a trustworthy machine shop or have Mark handle the job for you. Disclaimer - Mark’s not the only one but he’s made it really easy for a bunch of really happy people.
If stroking your small block (yup, I said that) doesn’t interest you, without question, go big block so you have nice drivability to go along with the power
I’m a small block stroker (is that a noun or adjective?!?) guy but my build was done over a decade ago before Mark made this easy! I have a very conservative build and this engine pushes the limits of what I can hook up on street tires, runs a low 12, great manners, quiet, gets good mpg depending on driver discipline and I could jump in it and drive cross country tomorrow morning. If there’s any disappointment it’s that I spend most of my time at “tip in” throttle, driving around town at 1500-2000 rpm, but thats why IMO you build for torque, not horsepower.
There’s lots of ways to skin a cat, these were the first two to enter my head. See what others come up with.
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Last edited by bccan; August 31st, 2022 at 01:21 PM.
I'm very skeptical about "rebuilt" Oldsmobile engines. There's literally a handful of people in the country I would trust to build one.
That said, I think you would be very happy optimizing the output of your 350. A basic compression bump, cam, intake, and exhaust could be night and day over a base, factory 350.
A 455 will not give 375-400 HP out of the box. A 70 442 was something like 325 net horse. So, to get that HP out of a 455, it, too, will need work. And, that is ok, for sure, but it won't just be plug and play.
If you're looking to make a street fighter, the only downsides to the 455 are the heavier front end and the increased gas consumption, and maybe increased cooling needs. Like said above, a 455 will handle your power needs with much more grace. It's worth noting that the "built small block" factory race cars were for specific limited race applications, and insurance dodgers. So, if you truly want that much power, then going with the 455 is better.
However, if you'd just like *some* more power, while maintaining your 350, perhaps optimizing it would work. Maybe you could build that 350 up to a nice, fun, but friendly power level, then, if it didn't satisfy, build a 455 later and sell the 350 once swapped and evaluated.
The con of a 350 is regretting it isn't a 455...but seriously a good running 350 with the compression bumped a little, some headwork, cam etc. is very respectable. If I already had the 350 I'd stick with it.
Torque is everything. Stock 455s made 500 lb/ft. You can burn tires forever with 500 lb/ft. And they bolt right in where your 350 is now, and you can hook up all your accessories
I say build or stroke the 350. The stroker easily hits 400 HP/500 ft/lbs of torque. I know here, a good 455 core usually go for a grand. That goes a long way to building a 350. Plus, you really want to be very particular on who builds a 455, due to the big bearings and proper clearances used.
The difference in weight between a small block and big block in next to nothing. If the small block has a iron intake now, put an aluminum intake on a 455 and the big block will probably weigh a little less.
It’s hard to beat the seat of the pants feeling of a torque monster 455. A 400hp small block is going to have a much more “grumpy” disposition. It’s going to need more camshaft, which means more converter, more gear, etc. A 400hp 455 will be much more pleasant. You can get away with a much milder converter (or a mild aftermarket replacement) and the torque will overcome a less than desirable rear gear.
The only hangup will be cooling system. You will most likely need a better radiator, especially if you have A/C.
A 455 will bolt in exactly where the 350 is now. All the accessory brackets will interchange. Before Joe P comments, I’d recommend reading his numerous posts about engine/frame mount compatibility.
Steer the front end with the steering wheel. Steer the rear end with the throttle!!!
A radiator upgrade is a good idea no matter which way you go. I went with the Autocity 2 core aluminum with 1 1/8" cores. It has the stamped tanks, it would look stock painted black. My 9 to 1 403 never goes above 170, has a 160 high flow Robert Shaw thermostat in my 70S. What is your budget? What do good 455 cores go for in your area? The 350 stroker can be numbers matching and hide smile inducing fun inside. I am a big fan of the SBO, the Olds 350 is a great motor from new. The stroker 350 crank only weighs the same as a 330 forged crank. A 403 is fine with excellent torque, just finding a good one is key. You definitely want your cooling system in perfect shape with either a 403 or 455. Both are usually the motors we seem to have run hot in our Olds.
August 31st, 2022, 11:52 AM
