Before anyone clobbers me: I know the THM200 and THM200R4 could be made to be good, but that usually came after GM had much to do with building them. Same goes for the THM325 and THM325-4L

Wow, clampless hoses!

Your electronics owes made me cringe. They had these issues while still fairly new. They can be fun to chase. Not the good kind of fun.

Regarding the gauge cluster, you might be able to swap in a Riviera mechanical speedometer cluster. It would probably have to include all of the surrounding plastic and vents and lights etc.

No WOT on the 4.1 I agree will make it last nearly forever. The head-gasket issues were a combination of engineering thin cylinder walls, drivers who expected it to be an appliance and treated it as such, and heat (my exposure was in the west-coast beaches and deserts). I wonder if it is possible that your car was one of the V8-6-4 units that, upon failure, had the 4.1 "big V6" replacement that GM was doing for a lot of those? I don't know if they put the V8-6-4 in the Seville, but all of the other Caddys got all of the other Seville engines so maybe . . . ?

Cathedral club... The V8-6-4 engine, as far as I know, was prevalent in the 1980-1982 Seville'*. Most issues with this conglomeration were solved by cutting the wire so it ran on 8 cylinders all of the time and was a relatively a good engine. It was a 368 cu in with real power and hard to find now. Most of the 1980-1985 4.1 V8 engines were subject to cylinder wall problems because the walls were so thin. That problem was addressed in 1985 and those engines turned out to be pretty reliable with the block and head bolt situation addressed by the factory.

Seems like the 4.1 engine was good for 50,000 miles before it had problems and, recognizing this, GM replaced them under warranty although you got the same thing until 1985 when they recast the block. For 1980-1984 sometimes you got a good one; I met a couple of 4.1 owners who were still running well over 100,000 miles. Luck of the draw!

Anyway, would like to find some other owners with the 1980-1985 cars to compare experiences and parts locators/suppliers or even their excess stuff laying around.

Thanks to all for the input and hope you keep it coming!!

Ah yes, I always forget about the Cadillac 4.1 V8 those years. I guess since it was only in Cadillacs it didn't cross my radar like the others that were shared about through Cadillac and all the others.

Glad to have you here, keep asking questions! . . . and maybe throw a pic of that beauty up here.

Continuing saga on my '83 Seville... Just found a radiator leak and after pulling the rad, deduced that it was beyond repair. So, like anyone else, went to the computer and ordered a new aluminum replacement unit from a very reputable supplier. The one I got was not applicable to my car (old stock closeout) and initiated a return/exchange for another mfg'* product. While everything was open and accessible, decided to replace the (usually) plastic timing indicator which was missing. Since being plastic, it was either not reinstalled when the motor was replaced or broken when the new water pump was installed or just became brittle with age and fell apart. Part #1623830 (GM) no longer available, of course, so to the junk yard I went. Originally sold for less than $10 when new, the junk yards want from $50 to $150 for plastic one. Rip-off artists!! Found one, supposedly metal, for $89, still undecided on that.

Found a working digital replacement speedometer reasonably priced, does the same thing mine did so my speedo was not at fault. Also replaced the GM 25007220 speed sensor from speedo to VSS buffer.. Try to find one of these suckers! That wasn't the problem either, put mine back in. AHA! no power to the buffer. Currently tracing the wiring from fuse to 56 connector to buffer to CC switch to ignition switch to ECM to cruise control to brake switch. Raining, can't work on it right now. Fun job!

Several other things in need of repair so I'll keep posting if anyone is interested. But I need information on something I have been considering. Question: Can I replace my digital speedo with an analog one? I'm thinking I would have to replace the computer to effect the electronics change and would the new ECM have to be programmed? Just a possibility in mind as an alternative to having a dealer trace my electronic issues.

Any suggestions would be appreciated. And who has a 1980-85 Seville with whom I can swap stories? Later, Norm

My heart gets warm every time i see this video LMAO

I am definitely interested!

I don't know if the Eldo had a non-digital option, but the Riv did so it could be possible there is a feasible way. The clusters are different shapes and humoring the idea of swapping surrounding dash pieces across yields the fact that the pseudo-woodgrain is different from Buick to Cadillac.

Well according to the source my father and others GM used NOVA modified frames to build the short Cadillac with the weird trunk.
My father said go check out the two frames they used the same frame rails other family members worked at the GM plant the frames came from they saved millions not to have to buy new tooling.
Wikipedia did not work at the GM plant now did they?

REGAL GUY
For what it'* worth, in my travels today I stopped at a Collision shop and talked with the owner who remembers stuff he worked on back in the 70'* and 80'*. To his recollection, the Seville (and possible other models of Caddies) could very well have used the frame rails from the Nova as you suggested. He, however, remembers distinctly that the PLATFORMS for the Nova and Caddy were different, hence different configurations between the finished frame Nova vs Caddy. That might be where the confusion came from, frame rails the same but different cross members, gussets, etc. So you are possibly correct as well as CATHEDRAL CLUB being correct also. I remember back in the 70'* my Dad'* caddy needed lower ball joints and my buddy at the parts store gave me the Moog ball joints for a Chevy which were the same thing only packaged, and sold, at different prices. GM is notorious for saving money by using parts from one badge to another to save them money. You might buy a Caddy in looks but the guts could very well be supplied by Pontiac, Olds Buick or Chevy. Case in point, through EXTENSIVE use of the internet, I'm finding parts for my '83 Seville are also used on the other GM badges.

CATHEDRAL CLUB
You piqued my interest with the Riv dash suggestion. I called around and found two models I'm going to look at to see if it is feasible to swap dash parts and accompanying gauges, etc. without spending a fortune. The Riv parts, at least in this area are more readily available than the Seville of my era. For all of the bad mouthing the 80 to 85 Seville'* have received, mostly referred to as GM'* "deadly sin", there should be tons of them in junk yards but that is not the case. I'm wondering why unless all of them have been sent to the crusher.