Cadillac V8-6-4 engine?

John Royark JR

PCS Member
I recently looked at a 1982 Cadillac formal limousine that has the V8-6-4 engine. I have heard horror stories about this engine, but would like to hear other experiences with this engine.
Please respond ONLY if you have personally dealt with this engine. (The reason I say this is I know how horror stories spread, like the 4.1 that everyone is leary about, I found my experience with both FWD and RWD ones are very favorable), so I am looking for first hand reviews.
I know Cadillac only used it for one year, except the limousine, which it was the standard engine for a few more years. This car has 115,000 actual miles.
Is it a good idea, or should I steer clear?
I have also heard you can dissable the function, anyone done that, does it help?
 
I don't know if it is true but i have herd that as long as you disable the function, the motor runs great.. I was under the impression that that motor was in the 81 to 86 cads... Total speculation here.. Never had one..
 
I don't know if it is true but i have herd that as long as you disable the function, the motor runs great.. I was under the impression that that motor was in the 81 to 86 cads... Total speculation here.. Never had one..

My bad, I looked in my Cadillac book after I saw your post. 1981 and 82 had the V-8-6-4, except the limo which used it from 1981-84. 1985 the limo went to FWD and used the 4.1.
 
v8-6-4

sir, i have sold a LOT of these cars and the best thing we ever did was cut the pink ? (dont remember) wire going to the distributer and made it a 8 cyl. only. worked for me and sold many caddys and like all alum. headed engines just never let it run hot. my experience any way.
 
I had a 1982 Cad 36" Corporate stretch Limo with one in it, and had no trouble with it. It was a great car and I liked it very much...........Car started life as a 4-dr sedan, I think...
 
I have had several of these and understand they were same as 368 engine which was a great motor. All I had was already fixed to stay in V8 mode and were all great cars, no issues. If one is still hooked up and in good working order they are ok too but that is not the usual case.
 
I have had, and still have, personal experience with the V8-6-4 engine, and as is typical with this particular subject, there's lots of misinformation from people who think they know what they're talking about, but don't.

First off, the V8-6-4 was one year only, that year was 1981. Period.

I learned to drive on my mother's 1981 Sedan DeVille, and my Bayliff Cadillac hearse was built from a 1981 Sedan DeVille, so I've been familar with the V8-6-4 story for as long as I've been driving. By the way, the V8-6-4 in my hearse is still working as GM intended!

Secondly, the V8-6-4 was NOT a unique engine! It was a unique fuel injection system fitted to the Cadillac 368 V8. The 368 was available in 1980 and then again from 1982 thru 1984 with carburation. Additionally, the 1981 commercial chassis, which also used the 368, retained carburation. Only the 1981 passenger cars received the V8-6-4 fuel injection system.

The 368 is a good motor and I would not worry in the least about one having over 100,000 miles on it. It was the fuel injection system that got the bad name, not the motor.

The fuel injection system was based on the car's speed, so that the faster you went, fuel would cease being admitted to two cylinders, and then two more cylinders. There was a sensor in the transmission to guage the car's speed, and disconnecting the sensor from the fuel injection system, which literally is as simple as cutting or unplugging a wire, fooled the system into running as full time V8.
 
I have had, and still have, personal experience with the V8-6-4 engine, and as is typical with this particular subject, there's lots of misinformation from people who think they know what they're talking about, but don't.

First off, the V8-6-4 was one year only, that year was 1981. Period.

I learned to drive on my mother's 1981 Sedan DeVille, and my Bayliff Cadillac hearse was built from a 1981 Sedan DeVille, so I've been familar with the V8-6-4 story for as long as I've been driving. By the way, the V8-6-4 in my hearse is still working as GM intended!

Secondly, the V8-6-4 was NOT a unique engine! It was a unique fuel injection system fitted to the Cadillac 368 V8. The 368 was available in 1980 and then again from 1982 thru 1984 with carburation. Additionally, the 1981 commercial chassis, which also used the 368, retained carburation. Only the 1981 passenger cars received the V8-6-4 fuel injection system.

The 368 is a good motor and I would not worry in the least about one having over 100,000 miles on it. It was the fuel injection system that got the bad name, not the motor.

The fuel injection system was based on the car's speed, so that the faster you went, fuel would cease being admitted to two cylinders, and then two more cylinders. There was a sensor in the transmission to guage the car's speed, and disconnecting the sensor from the fuel injection system, which literally is as simple as cutting or unplugging a wire, fooled the system into running as full time V8.

Patrick, I agree totally and learned about the fuel injection versus carb. as I didn't know that info. Sounds like you know for sure how it is.
 
In 88-89 I worked for a limousine service & we had an 84 Armbruster Stretch limo with the V8-6-4. The system had been disabled but the car was a real gutless wonder.
 
I had a 81 Seville and it had this feature. We dissabled the multi funtion and the motor was gutless but it ran well. I sold the car a year later and they put it back to the 4-6-8 and it cratered about 10 months after they did that. I think they ran it our of oil. It is not one of my favorites, I would rather have a 472 or 350. The motor was replaced by them and they put in a 267 out of a 79 Monte Carlo.
 
I had a 1981 (only year for production cars) eldorado with the V 864. The engine mechanicals are great. that is not the problem. The 368 engine is fitted with special heads that would close the valves when it called for it to run on less than 8 cylinders. The fuel injection system is nothing fancy and the same system used on other years ( throttle body with 2 injectors). The problem I had with mine was the computer and the wiring. This is an extremely complicated system and the diagnostic procedure is very time consuming even if the system is locked into 8 cylinder mode. The throttle body was a source of alot of problems also with all the sensors and vacuum hoses on it. the smallest vacuum leak would create many problems. If there is a problem don't plan on taking it to anyone because they will not know what to do with it.
 
'81-'84 Limos have the V8-6-4

Patrick: from what I understand, the V8-6-4 is not 1 year-only if you consider the '81-'84 Series 75 Limousines.

Here what I am under the impression of:

1980 Eldorados & Sevilles = 368 *plain EFI* (Olds Diesel was available) (No carb 386 was available on FWD models). In Cali. there was an Olds 5.7 (350) gas available in Eldos.)

1980 RWD Cadillac = 368 4bbl carb. (Buick-built 252 (4.1L) V6 & Olds 5.7L diesel were available).

1980-1984 Commercial Chassis = 368 4bbl carb

All 1981 Cadillacs could be had with V8-6-4

1981-1984 Series 75 Limousines = V8-6-4

1982 Cadillacs: HT4100 aluminum block

1986: Olds 307 replaced HT4100 4.1L in RWD Cads.

So hearses kept the carb through '84, while limos got the V8-6-4. I have seen a couple limos in person and can confirm the ones I saw were V8-6-4.

Here is one: http://www.vehiclesbyseller.net/1984-Cadillac-Fleetwood-Formal-Brougham-Omaha-Nebraska-68114/4012944

I have had a couple '80 368 4bbl Cads, and had good luck with them. The Coupe DeVille & Fleetwood I had were fairly gutless, but I think that was more to do with the 2.28 rear gears than anything else. My '80 commercial chassis with factory 3.08 ratio is much more pleasant to drive.

Had 2 V8-6-4 Cadillacs. One I owned briefly, and had been made to run 8 cylinder all the time. No issues of note. The other was the same way, but the oil had been diluted with fuel and had a severe bottom-end knock. The oil had the consistency of gas and reeked of fuel. Not sure if a computer error caused this, or? I knowingly bought the car that way because the body was mint, and installed a 4bbl 1979 425 (direct bolt-in).

Drove for a bit and sold.

Good friend has a Coupe DeVille with V8-6-4 and had many headaches. Car now sits out of frustration. However, that car had sat neglected for years before he owned it. I think it has much to with the care the car has recieved over the years.

All in all, I'd prefer a 4bbl 368. (6.0L) but the V8-6-4 is found in some beautiful models, has an overblown bad-rep, can be made into a plain 8 cylinder easily enought, comes attached to an 8.75" rear end, a THM400 trans and is a direct swap for any Cadillac big block if things turn sour.
 
Patrick: from what I understand, the V8-6-4 is not 1 year-only if you consider the '81-'84 Series 75 Limousines.

Here what I am under the impression of:

1980 Eldorados & Sevilles = 368 *plain EFI* (Olds Diesel was available) (No carb 386 was available on FWD models). In Cali. there was an Olds 5.7 (350) gas available in Eldos.)

1980 RWD Cadillac = 368 4bbl carb. (Buick-built 252 (4.1L) V6 & Olds 5.7L diesel were available).

1980-1984 Commercial Chassis = 368 4bbl carb

All 1981 Cadillacs could be had with V8-6-4

1981-1984 Series 75 Limousines = V8-6-4

1982 Cadillacs: HT4100 aluminum block

1986: Olds 307 replaced HT4100 4.1L in RWD Cads.

So hearses kept the carb through '84, while limos got the V8-6-4. I have seen a couple limos in person and can confirm the ones I saw were V8-6-4.

Here is one: http://www.vehiclesbyseller.net/1984-Cadillac-Fleetwood-Formal-Brougham-Omaha-Nebraska-68114/4012944

I have had a couple '80 368 4bbl Cads, and had good luck with them. The Coupe DeVille & Fleetwood I had were fairly gutless, but I think that was more to do with the 2.28 rear gears than anything else. My '80 commercial chassis with factory 3.08 ratio is much more pleasant to drive.

Had 2 V8-6-4 Cadillacs. One I owned briefly, and had been made to run 8 cylinder all the time. No issues of note. The other was the same way, but the oil had been diluted with fuel and had a severe bottom-end knock. The oil had the consistency of gas and reeked of fuel. Not sure if a computer error caused this, or? I knowingly bought the car that way because the body was mint, and installed a 4bbl 1979 425 (direct bolt-in).

Drove for a bit and sold.

Good friend has a Coupe DeVille with V8-6-4 and had many headaches. Car now sits out of frustration. However, that car had sat neglected for years before he owned it. I think it has much to with the care the car has recieved over the years.

All in all, I'd prefer a 4bbl 368. (6.0L) but the V8-6-4 is found in some beautiful models, has an overblown bad-rep, can be made into a plain 8 cylinder easily enought, comes attached to an 8.75" rear end, a THM400 trans and is a direct swap for any Cadillac big block if things turn sour.

I had a 84 75 series limo with the V8-6-4 engine also which was unplugged and always a V8. Great car and still owned by PCS member in Maine somewhere I believe.
 
never had one but from what I was told the bigest problem in the system was the lack of traning for the personal needing to work on them. as all ready relayed.
 
The biggest problem I remember with this engine was a shudder when cylinder activation/deactavation took place. And only one car, a green Sedan Deville that the dealership I worked at traded for.

We performed the modification on that one as we worked on it for several days with no success. The tech that was assigned took it as a personal challenge but finally threw up his hands with that one.

That car IMO was rode hard and put up wet many times, typical rancher car.
 
My bad, I looked in my Cadillac book after I saw your post. 1981 and 82 had the V-8-6-4, except the limo which used it from 1981-84. 1985 the limo went to FWD and used the 4.1.

I just checked my Cadillac book for the third time, I was correct in my original thread starting post, I read it wrong when I made the post quoted above, it was only used in 1981, EXCEPT limo which used it from 81 through 1984.
It was a 368 as Patrick mentioned, with added features. Here is what the book says on how it worked: a microprocessor determined which cylinders were not needed at the moment. Then it signaled a solenoid actuated blocker plate, which shifted the rocker arm to pivot at a different point as usual. Therefore, selected intake and exhaust valves would remain closed rather than operate normally. Valve lifters and push rods went up and down as normal, but uneeded valve pairs stood still.

Im not concerned as HOW it functions, but just how good and reliable the engine is to know if buying the limo is a good idea or not.
Thanks to those that replied with ACTUAL experence with this engine, keep em coming if you own or owned one.
 
v-8-6-4

If you can find a copy of Hemmings Classic Car Volume 4 Issue 7- April,2008 you will find a great article on this engine .it was too far ahead of its time as we all know some the companies are using the same ideas today.
 
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