The 350 Olds in my '49 Cad with a '77 Seville clip is getting a bit long in the tooth, so am thinking about replacing it with a little more HP....would a 403 Olds or a 455, be a pretty much bolt in, and bolt up to the TH 400 I have now? Thanx in advance for any input.
One of the first car things I ever accomplished! Not in a cool Caddie, but I swapped a junkyard 455 out of a wagon into a 73 Cutlass with a 350 in 1983. I knew almost nothing at the time and as I recall it was easy. Not much help but I thought I would add my $.02. I will be interested in the replies because I don't view the 455 as a big block like a 396 Chevy with big heads. 455 V8s have a higher deck height to accommodate a 4.25" stroke crank to increase displacement. These taller-deck models are commonly called "big-blocks", and are only 1" taller and 1.5" wider than their "small-block" counterparts.
go for the 455 , pretty much a bolt in and will bolt to your TH400......403 is a sb ....400, 425, 455 is considered a bb in the Oldsmobile world... You will love the torque of the 455 that the 350/403 just doesn't have...
A shop I worked at in the 80s specialized in converting olds and cadillac 350 diesel powered cars to gas power. The 455 will bolt right in where the 350 olds used to be . Even the accessory brackets will bolt up .
A 455 is a direct swap, but if you are using 350 frame perches, headers may not clear. The 455 perch is just a little taller. It's easy to space it from the frame tho. Other than that it's a direct swap...
The engines will interchange, mounts and all I would get the brackets with the new engine however, different water pumps will require different brackets. I love the 455 in my convertible
Pretty simple swap I have two cars with a 455s and replaced a 350 with one and am very happy I did! A 455 should get the Caddy down the road just fine! Joe
IMo 455 over 403 , I do not like the lower end design of the 403 window blocks ... and like the old saying goes , nothing beats cubes ....
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