1989 Coupe Deville

[Jeeper89]

Hello
I just inherited a 1989 Caddy Coupe DeVille. My father and I always joked around with making his 89 Caddy just a little quicker without doing a complete motor rebuild. Any suggestions?  I would like to do somethings to the car in his memory. We both loved this body style ( this is our 8th Caddy in this style ).  Any suggestions would be appreciated. Thank you

[TJ Hopland]

I don't think there is anything easy.  That was the second year of the 4.5 which was more or less the same as the 4100 and used the same throttle body injection system.  In 90 they changed to a sequential multiport injection system and raised the compression.  91 they increased the displacement to 4.9. 

I would presume the basic mechanics are similar enough that swapping to the later 4.5 or a 4.9 would not be too bad but where it usually gets to be more of a hassle is the electronics.  You would have to look close and see if the bodies were identical enough to allow you to transplant the ECU and harness complete with the engine and possibly trans.  If its all the same then it may not be too bad but if there were minor changes that could mean you would have to modify or re make the harness which isn't for everyone.    You then have issues like changing from low pressure to high pressure fuel pump.   It may or may not be a drop in replacement, same with the fuel lines, they may work or have to be replaced.  If you are going through that much trouble you might as well look at a Northstar or supercharged 3800.           

[smokuspollutus]

There are next to no "speed" parts for any 4.X Cadillac. Try advancing the timing to about 12 or so. Usually you can get to 12 and still run regular gas. Better takeoff and more MPG.

[Jeeper89]

I figured. We were just joking around as we were working on the other cars. I appreciate the help and advice. I'll probably just clean it up, and add some Cadillac accessories ( continental kit, skirts, etc... ) and just enjoy the car.
Thanks again!!!!

[TJ Hopland]

I forgot there was a 'hot rod' version of the 4100 and 4.5,  it came in the Allante.   It had a unique to the model tuned port intake and I think was sequential multiport from the start.  I think it also came with tubular headers instead of standard exhaust manifolds.   All that got you around another 50 hp which is quite a bit considering you were starting in the 130-150 range.   I think it was also among the first cars with the electronic shifted auto transmissions.    No idea if it would be at all practical to swap that stuff into a 'regular' Cadillac.   First challenge would be to find a good donor.   It wasn't an especially big seller, only a few thousand a year.   For such a rare engine its interesting that they include the gaskets for it in the gasket sets for the 4100, 4.5, and 4.9.  The intake gasket looks kinda like the Olympic logo.