Sammy64

I have a 1985 Cadillac Sedan Deville 4.1 liter motor that I want to put into a 1987 Cadillac Coupe Deville.

According to the Hollander Interchange Manual, this can't be done but they don't list a reason why.

Does anyone know why these two aren't interchangeable?

HandofDoom

It will fit.There the same engines.But if i were you I would put the 4.5L in.Its much more powerful and much more reliable engine.I'd go with that.That will probably fit better too.Id pay the extra cash for it.

jkinney

I'd have to agree, this is probably one of the more "troublesome" motors that GM produced. I just rebuilt mine this spring and spent WAY too much money on it. They are a wet sleeve motor, and tend to have coolant leaking problems. GM recommends their own type of "stop-leak" pellets to put in from the get go, and on 40-50k mile intervals. They also suffer from lack of oiling on the rear cam journal that will eat up the cam, cam bearing, and the distributor drive gear. They have a new cut available on the cam (aftermarket) that has a "spherical moon groove" cut into it that has a channel cut from it -towards the distributor. This will pocket oil and fling it onto the distributor to give it "some" oil while running. Without these mods, chances are slim of them lasting over 120k miles. Not impossible, just real slim. Good luck.

HandofDoom

Well,there not junky engines.Its just that GMs made much better engines.This was one of their not so good ones(the 4.1L).Ive seen some cars with these engines that have well over 200K miles but not very many hit that point.Your better of getting the 4.5L.Very good engine there.Like I said,powerful as hell and they run forever.Good luck with your car.