I've had it with the original engine and don't have any confidence in a rebuilt. Does any one know of a swap that will work or had done one? I had an 84 Buick Riveria front wheel drive with the Pontiac 307, 4 barrel carb that had lots of power yet got very decent gas milage. That would be my swap of choice. Looking for suggestions. Thanks

I have a similar thread labeled Engine swap need input. I have an 85 seville myself. What I was given by one guy(assuming the instrumentation on your eldo is the same as mine) was as such below-------V

http://www.cadillacforums.com/forums/ht4100-4-1-4-5-4/173634-4100-engine-change-need-input.html

The best I was told of was these -------

Bad news: The 4500 is not going to fit in your car. The 4500 was made to fit transversely and for your car, the engine sits longitudinally. However, you do have some other choices including:
403 Olds
350 Olds
6.2 Diesel
6.5 Diesel
5.7 Diesel (Not good choice)
3.8 Buick V6

The 403 could be made to work with all the electronics. However, it'll be hard on gas but have good power. The 6.2 diesel would get you 35+ mpg and would have even more power than the 403 with a turbocharger
or some head work but would have that diesel clatter.
-------------------------------------------------------------------------
Hope that helps

If it's RWD you can use almost any RWD engine available, ranging from generic 350 to LS1

If it's FWD you are basically stuck with the 4.x series with a replacement longblock under the existing manifold

I envy you and your car then sir. Lol.

The 85 Eldo is an E body car, so any E body, Toro, Riviera, or Eldo will provide all the parts to install an engine from a 3.8 Buick to a 403 Olds. Best to buy a diesel donor car to install an Olds gas V/8 engine. The Olds is a 307 a 350 or a 403. All share the same basic block with a diesel and will bolt to the Caddy trans. You need a diesel donor because you need the specific front wheel drive oil pan, oil pump and pick up, engine mounts and belt driven acessories as well as proper exhaust manifolds. Rather an easy swap assuming you have a donor car. One swap not thought about too often is the 4.1 V/6 gas engine in the 84 Cadillac with a 4 bbl carb. Same basic engine as the 3.8 V/6 in a Toronado.