BUT YELLING AND ALL CAPS WORK FOR HARD-OF-HEARING, HALF-BLIND OLD FARTS LIKE ME, YOU WHIPPER SNAPPER!!!! But, sorry OP, I don't know anything about Cadillacs.
331 are an extended bell block while 390’s are not. So at the least the transmissions are different. Also the exhaust ports on a 390 are much larger so the 331 exhaust manifolds will not fit.
Well the good news is it looks like both have rear sump oil pans. 331 being the red one 390 being the blue one. The early trans isn't going to bolt on the 390 and you would need to either buy a spendy adapter if one exists or use a Turbo 400 or maybe BOP automatic of choice behind the 390. Most likely having to fab or modify mounts.
After that, in any engine swap where the same exact series of engine is going back in the vehicle such as replacing a 283 Chevy with a 327 or 350 or a 292 Ford with a 312 you are going to run into some issues. Things to consider: Oil pan sump design and location. This is a deal killer on a lot of same brand engine in same brand cars as a lot of later engines had the sump on the other end of the pan. If the distributor is on the same end of the engine you are usually good, if it is on the opposite end you are in for a hassle most of the time. For those who are asking "what the hell did he mean by that?" the oil pump and distributor drive off the same gear on the cam on almost all engines and if you have a front distributor it means that the deep part of the pan is going to be in the front. That won't clear the crossmember and often the steering on a lot of rigs that came from the factory with an engine with a rear mount distributor. Motor mounts and how they attach to the engine and chassis. Bell housing flange design on the engine. = what trans fits or is there and adapter available? Outside dimensions of the engine compared to the old one. A lot of engines that are quite similar got quite a bit taller and V8's got wider when the stroke was increased moving heads and exhaust closer to things like upper control arms. Cylinder head orientation; meaning which head sits forward or behind the other head as they are never straight across even. The that should be an easy swap becomes not so easy when you figure that on the engine you took out the Number one hole was on the drivers side and that head was an inch or so forward of the passenger side and the one you are putting in has number 1 on the passenger side and the left head wants an indent in the firewall before the engine will fit.
A 1955 Cadillac hydramatic would probably bolt to the 390, as 1955 up engines are Not extended block. Hard to find. Super hydramatics will bolt up to 390, but you will need at least driveshaft mods done.
d2_willys is correct. I have two 331 Caddys both from 1955. Neither have the extended bell. I believe all '49-'54 engines have the extended bell but '55 and up do not.
Glad to see you still active and participating. Short answer to your question. Easiest and cheapest way is to use the transmission that came with the engine. or a same year or newer replacement. Adapting post 55 engines to any of the earlier transmissions to requires expensive adapters. Putting a high torque 390 in front of a 1950 vintage trans will be detrimental to its longevity, unless it is totally rebuilt to withstand the doubled h.p. and t.q. OR... is it that your '50 already has a 390 and you wish to return it to 331 power?
Like has been said, drive shaft, trans mount, exhaust. If you have a gearbox already for the 390 then maybe not much more than eng mounting. I have a 49 331 and a 59 390, not a lot of difference.
Thanks guys if its just that its a cake walk Ray from the land of taxes and morons Only car guys and bikers are smart
i put a 61 390 in a 54, exhaust hit the power steering box. i have a 63 with a 58 engine and i'm getting ready to put a 63 390 in a 51. older motor mounts will bolt on to 63's.
CTRL + scroll will make most things larger... Alas, it doesn't work on the one thing you really want larger. .bjb
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