I'm just a bit curious about the cadillac 4-6-8 engine, seems like there is next to no information about it on the internet, mostly just a lot of badmouthing...but I'm curious nonetheless:

1) What system was used to switch "off" 2 or 4 cylinders for improved cruising mileage? Any manual scans, etc that can illustrate it for me?

2) What gives these engines such bad reputations? What parts on them are prone to break or make them otherwise unreliable?

Here's a magazine article from 1980 about it:

http://www.sfu.ca/~ajgee/mags/864.html

I haven't read the article that Dave posted so forgive me if I repeat something that it has covered....
As I've heard, there weren't any major mechanical "problems" with the system. Cadillac wanted to keep the larger engines yet get economical fuel mileage. They may have rushed it to market a little too quickly without refining it.
Most people didn't like the way it felt when going from V8-V6 or from V6-V4. I guess they didn't think it was "smooth" enough for a Cadillac.

Do a search for it here. There are a bunch of people who have those engines and like them.

Here is one of those posts from way back......ssstealth posted some really good info.
http://www.cadillacforums.com/forums/showthread.php?t=2866&highlight=864

I thought it would be neat to adapt to another engine, and have it under manual control (no computer control at all, user selectible 4-6-8 modes.) Figure its just solenoids, should be easy enough to do....

my 81 works fine, i figure once i get my cruise control working properly it will be fine. it really doesn't change gas miliage that much unless i am cruising 55 and under, it hardley ever goes to 4 while cruising at 65-75.

on the information note i have ALL DATA and other service manuals (mitchal) they just dont cover that system, i won a factory service manual on EBAY but they guy never sent it to me. so i dont know what i will o if i ever have problems with it, i iamagine finding repair parts will be difficult at best...

I have the v-4-6-8 you speak of and the system on mine does not work anymore, it's 8 all the time. it's an ok engine but I'm building a 500 now to replace it. just cause I can http://cadillacforums.com/forums/images/smilies/thumbsup.gif

the only thing that really drives me up a wall is the fan belt setup.
I'm really going nuts with this. is anybody else out there having to work on your belt / pullies every couple weeks.http://cadillacforums.com/forums/images/smilies/banghead3.gif

my main problem right now is that when its cold it sets a trouble code and idles way high, let it run a few minutes turn it off and restart it runs fine.
other problem is there are times it wont restart after a long drive. i am leaning toward the Idle speed control or the TPS. just haven't had time to check it all out

other little nagging problems it the stereo resets everytime the done light comes on, leading me to believe there is a short either in the lights or a ground fault.
and the darn cruise wont work......

but hey it is an 81, what else would i expect......

I'm just a bit curious about the cadillac 4-6-8 engine, seems like there is next to no information about it on the internet, mostly just a lot of badmouthing...but I'm curious nonetheless:

1) What system was used to switch "off" 2 or 4 cylinders for improved cruising mileage? Any manual scans, etc that can illustrate it for me?

2) What gives these engines such bad reputations? What parts on them are prone to break or make them otherwise unreliable?


Basic answer is that people do not understand what they do or how they work so they dislike them.

Customers were leary of the "jerk" or "miss" when the system switched from 8 to 6 to 4 cylinders and the engine runs rough and vibrates in 6 cylinder mode so they thought it was going to break.

The 81 was also the first year for a Delco digital microprocessor in a car as the PCM....there were lots of wiring connector problems and the connectors at the PCM itself were not that robust. 12 volt wiring in a system that used millivolts did not work very well. Lots of electrical and electronic problems that had nothing to do with V864....nothing at all.

The V864 mechanism was bulletproof...totally.

The mechanism is really simple. It is a mechanism and solenoid controlled by the PCM that mounted at the rocker arm pivot point. When disabling the cylinder the solenoid moved the actuator that disabled the rocker arm pivot so the arm just moved up and down at the pivot point against a slave spring. Simple and easy. 12 volt stuff so it could be controlled with a toggle switch.

Nothing in the engine itself broke or was unreliable. The wire connectors were prone to corrosion causing the PCM to freak and the PCM connectors were not very robust. Clean up and seal all the wire connectors and the PCM edgeboard connector and it is very reliable.