I'll be getting another car soon and theres a 81 coupe deville for sale. Anyone know what it has under the hood? I hope its not a 4.1.

I don't think they started using the 4.1 until '82.
The '81 should have a 368, I believe.

"The '81 should have a 368, I believe"

and hopefully not the 8-6-4

Someone correct me if I'm wrong but.......don't the 368 and the 4-6-8 (8-6-4) use the same block? It was the electronics that made them different, right?

Someone correct me if I'm wrong but.......don't the 368 and the 4-6-8 (8-6-4) use the same block? It was the electronics that made them different, right?



I believe you are correct. I heard that some folks would dump that electrical gremlin.

´81 De Ville had three engines
- Buick´s V6 252cid, 125bhp
- troublesome V8-6-4 368cid, 140bhp
- and optional diesel engine - 350cid, 105bhp

´81 De Ville had three engines
- Buick´s V6 252cid, 125bhp

Don't you mean the 231 V6? A buick 4.1? Never heard of it!

Don't you mean the 231 V6? A buick 4.1? Never heard of it!
yep - Buick. I was "economy option":lol
90-degree, overhead valve V-6. Cast iron block and head
252 cu. in. (4.1 liters)
Bore and stroke: 3.965 x 3.40 in.
Compression ratio: 8.0:1
125bhp at 3800 R.P.M.
Torque: 210 lbs.-ft. at 2000 R.P.M.
4-bbl carburetor

´81 De Ville had three engines
- Buick´s V6 252cid, 125bhp
- troublesome V8-6-4 368cid, 140bhp
- and optional diesel engine - 350cid, 105bhp
It looks as though you are correct.
http://100megsfree4.com/cadillac/cad1980/cad81d.htm
Standard engine for DeVille and Fleetwood Brougham was the "modulated displacement" 368 cu. in. (6.0-liter) V8-6-4, with digital fuel injection. Optional: a 252 cu. in. (4.1-liter) V-6, provided by Buick. That V-6 had Computer Command Control and a knock sensor to adjust spark advance, as well as diagnostics. The Olds diesel V-8 was also offered.
I guess the 368 was never offered any way except in the V8-6-4 configuration.
It looks like the Buick V6 was the best engine offered.

If I recall, the 368 was without multi-displacement (MD, 8-6-4) in '80, in '81 the FW limos, and in the commercial chassis in '81-'83. The 368 MD was in all models except limos/commercial in '81, and then in limos from '82-'84.

I'd rather have a 368MD than the Buick V6 because I'm pretty sure the MD can be disabled (although some people find it to work fine). Plus it would probably be easier if you ever feel like swapping a 500/472 in. The Buick V6 and the HT4100 just don't put out enough power for a 2 ton Cadillac in my opinion.

The Buick V6 CAN actually be beefed-up quite easily, and YES it was 4.1 liter 4bbl. The 368 was available with or without the MD gear depending on the year. As I recall, the '80 was the NON-MD and the '81 was MD. We had all Fleetwood Formal Limos back then as for Cadillacs and our 81's had the MD. And it IS very easy to disable.

ive heard alot about the buick 4.1 v6 , and ive heard it was available as a turbo in some buicks , ill do some research on it after a bit , why this never took off i dont know i imagine a 4.1 turbo would give more torque than the 3.8 turbo in later turbo buicks (outside gnx)


EDIT !!!!
Yes , there was a 4.1 turbo v6 , couldnt remeber where i heard of it , it was int he buick rivera indy 500 pace car , apperently it was the only 4.1 turbo ever made and since Tom Sneeva probably got it after winning the 500 (the winner ususly gets the pace car or a replica ) , the riveras probably in a museum somewhere or if sneeva didnt get it its probably in the back of a GM wharehouse sitting next to the 85 fireo pace car and a couple of beretta convertables from the 1990 500

OK, Here is the real scoop on the V-864. The non modulated version of this engine WAS installed in the 1980 model. Apparently all of the electronics were not worked out yet. In 81, they went full force with this thing. It had digital fuel injection, electronic on-board diagnostics AND an analog back-up computer if anything went wrong.

I found the system to be very reliable and drove my 81 Fleetwood 330,000 miles with NO trouble. As a matter of fact, the second owner of this car since I sold it is STILL driving it. The only thing he has replaced on the motor is the distributor drive gear. 420,000 miles!!!

As for disabling the system, this is very easy. The key is knowing how the thing works to begin with. The computer measures load/torque requirements and when conditions are right, begins to shut off cylinders. This is accomplished by rotating a turret shaped contraption above the rocker arms allowing the rocker to raise up from the head. This action leaves the valve closed on that cylinder. With the valve closed, the same air/fuel mixture is continuously re compressed, keeping the cylinder temperature up and of course, not taking in any more fuel.

The key is that NONE of this happens until the car is at cruising speeds. This was determined by a signal from the transmission that it was in high gear. To disable the system, reach under the car and from the driver's side and snatch the 2 wire connector from the side of the transmission... you now have a full time V8. No codes, no lights, no problem.

Now what I did that I thought was a bit more elegant was to intercept this wire with a switch at the dashboard. It is simply a ground signal to the computer so no fancy voltage crap is required... just splice and go. With the switch in place you can run V8 as much as you want and then when you get stuck in the middle of nowhere looking for a gas station you can flip it on and return to the "32 mpg mode"

As for the complaints from the general public... hell it was new and everyone complains about that. At the time, American cars with 4 cylinders engines just were not good PR, especially in a Caddy. The other problems again had to do with the operation of the system. When you got up to moderate speeds the car would shift from 8 down to 6 and finally to 4 cylinders. The 6 cylinder mode was unbalanced feeling even though it was only in this mode for short periods of time. I think they would have been bettter off to have it drop from 8 to 4 like they do now. (YES, this is how today's Northstar engine handles driving without coolant, exept both valves are OPEN instead of closed) The other thing that made driving this a bit uncomfortable was the fact that when you coast to a stop, there is always that point when the governor in the transmission shifts down from 3rd to 2nd gear. In most automatics, you never feel this happen. At this point the engine was instantly returned from 4 cylinder operation to 8, creating a slight surge even at zero throttle. If you are not comfortable with the car and have a really light braking foot (typical 70yr old demographic) this could be scary.

Remember that the 368 is just a smaller bore version of the bulletproof 425 engine used from 77 up to 80. Buy the 81, complain about the V864 to get the price down, take it home, snatch a wire, and drive the hell out of that car. It will do good for you. If you really want something good, hold out for a Fleetwood Coupe. These things are getting REALLY rare.

GOOD POST !!!!

i never knew much about the 864 , or its operation , just the grumbles over quaility

as for nowaday uses it found a home in a upcoming 5.3 litre chevy truck engine , i think gm is getting ready to stick these in silverados

I'm telling you, is this guy a wealth of knowledge or what? :thumbsup:
Great post Bill.

Stop it Kevin, you're makin' me blush...

Another thing about the 81's that I forgot about that is really great.

The on-board diagnostics on these cars was actually VERY useful. Unllike the current Fleetwood systems which give information only, the system on the 81 would allow you to scan multiple systems and see values for things like temps, injector pulse widths, timing, etc. It also had ways of testing every underhood switch, selenoid, sensor, etc. from inside the car. It made working on the car a real dream.

Of course to make use of these things, you will have to purchase a REAL GM service manual for it, but trust me, it is worth every penny.

Yep, "Output Cycling" is a rather useful thing when you are trying to diagnose certain issues. The DFI system was the first of many OBD systems on Cadillacs. Unfortunately, only the RWD Fleetwoods strayed away from that type of system, all the FWD cars remained with that degree (and greater) of OBD. Viewing operating "parameters" is just the tip of the diagnostic iceburg which would become available to the customer (and would-be mechanic) on later FWD Cadillacs.
A while ago, I posted some info about these systems and I will reiterate that you CAN gain a rather in-depth guide to their inner workings through a small "Quick Reference Guide" available through Helm. It cost $7 for each year, and covers every model available in that year.

Kevin,

Is this available for the Fleetwood? The only "advanced" parameters and readings I have been able to find is the 05 and up codes, most of those dealing with AC readings.

I do use 14 occasionally as yet another speedometer check ;)

according to what I just read, the V8-6-4 feature seems real god and cool...... V8 power when ya need at, but cruise on the highway and get 32mpg....... why was there soo many problems with it?

the 368 seems to be underpowered though, 160hp?

seperate question, between the 425 and 500, which is better?

say if you got a '77 CDV and you wanted to make a big sleeper, keep the 425 and build it up, or swap in a 500 and build it up?

Some people have had no problems with the 8/6/4, I dunno why it acts up some times.

That hp measurement is probably nett, so it will seem lower than what they used to use (gross).

I'd say go for the 500. If you're looking at nitrous, the 425 crankshaft might not take it. Plus Edelbrock makes an aluminum intake for the 500/472, though you can't use the stock AC compressor with it. And the 500 is bigger, therefore it's inherantly going to be more powerful.

The apparent "failure" of the V-864 was due to a few different things.

First off, our federal government, in their infinate wisdom, would not allow the true mileage of this engine to be posted on the EPA sticker. EPA held that there was no eveidence to properly assertain how much time the engine was in each mode. So since this value could not be agreed on, they formulated the rating on the car being in 8 cylinder mode all of the time. This was not aided much by GM either. They pushed for a ruling on the "MPG Sentinel" as well stating that since the driver could VIEW the mileage while driving, that his driving habits would improve, thus getting BETTER mileage. EPA didn't buy into this argument either.

With pressure from CAFE requirements, and NO help from EPA, the engine was dropped in 1982 for the puny underpowered HT4100. It was still silently placed into limos for a few more years.

Now, since the engine was dropped after only a year, the general public immediately came to the conclusion that the engine was unreliable. Remember that this was an era where anything advanced that did not come from Japan was labelled junk. This was also a time when Quaker State was running ads stating how their oil was good for 15,000 miles between changes. The only mechanical complaint I could think of on this engine was that the 6 cylinder transition mode was a bit unbalanced.

I guess my point is that the "general public" does very little thinking for themselves. They hear one person talk and that it repeated as gospel from that point forward. You need only to look around to prove this point. Is the McDonald's hamburger the best burger ever? Is a Taurus or a Camry the best car? If you buy a minivan to have more room, then why is all of your luggage on the roof?

I guess I should not complain... If the entire world were populated with geniuses, who would be left to cook our fries? :D

I had an 81 SDV with the V8-6-4 and loved it. I put over 125K miles on it, sometimes towing a 6000+ lb boat with it. I did not disable MD - it had lots of power and yet got great mileage on the freeway. As the other guy wrote, it had a little vibration in 6 cyl mode, which you rarely used (cruising up a slight hill would use teh 6 cyl mode). And the On-board diagnostics (OBD) were great as well. I would drive with the OBD turned on and push the buttons to turn off 6 cyl mode is I was going to be at it for a long time. The switch idea is a good one. I also had an 81 El Dorado with the MD V8. Loved it too. I developed an overheat problem which I never solved and finally sold.
I still have the genuine GM shop manuals if someone wants to make me an offer. Write me. john_sullivan(at)BMC.COM.

my '93 DeVille has all that cool OBD stuff, I have a factory service manual and learning about it, it really makes working on the car nice.

Just hearing about all this makes me want to get a V8-6-4 powered car, they seem really cool and interesting to run.

Lux Hauler,
The blocks are different as the V8-6-4 block doesn't have the hole machined for a mechanical fuel pump. Everything else is the same on the block. The intake, valve covers and additional V8-6-4 components are different/added.


Pat

Someone correct me if I'm wrong but.......don't the 368 and the 4-6-8 (8-6-4) use the same block? It was the electronics that made them different, right?

Vanasia,
Have you ever owned a V8-6-4? If not, please reframe from calling it "troublesome". If you want to call any engine troublesome, start with the 4100 followed by the Diesel. How many of either make it to 100,000 miles? I have two perfect working examples and love them both (192,000 and 139,000 miles). Besides having four bad 4100's, two of which just barely breaking 100,000 miles, one going through two engines by 100,000 miles, and the fourth going to 129,000 miles with proper maintenance (I bought the car at 66,000 miles), I have had one with the Buick 4.1 that threw a rod at just over 100,000 miles. Another Buick 4.1 powered car, my current summer daily driver, had it's engine replaced BEFORE the 78,555 miles I bought it at with a '72 500 already installed.

Pat

´81 De Ville had three engines
- Buick´s V6 252cid, 125bhp
- troublesome V8-6-4 368cid, 140bhp
- and optional diesel engine - 350cid, 105bhp

Stoneage_Caddy,
Of the engine options from 1980 to 1982, the best, believe it or not, was any of the 368's, including the '81 V8-6-4. Although the modulated displacement system might be unworking or disconnected, they are still running. The Buick V6 and Olds Diesel powered have long since either had their engines replaced, or been scrapped.

Pat

"The '81 should have a 368, I believe"

and hopefully not the 8-6-4

Lux Hauler,
I am disappointed at you. As a member of the MTS board, and having an engine in the 368 family (368/425/472/500), you should know better. The 368 was the BEST engine available in any Cadillac from '80-'81 (through '84 in Limos). In 1982, the 4100 was the standard engine and the Olds Diesel was an option.
How many Olds Diesels are on the road today? How many 4100's have been had their head gaskets replaced or engines replaced? What's the biggest problems with a V8-6-4? That the V8-6-4 system quits working? At least the car is still being driven.
I have owned four 4100 powered cars, two Buick 4.1 powered cars, two V8-6-4 cars and one carbureted 368. Of them, the ONLY two still running with their original engines are the V8-6-4 cars. Additionally, I have replaced the bad 4100 in my '82 Coupe with the carbureted 368 out of a very rusty '80 Coupe. One of the 4.1 V6's threw a rod at 103,000 miles. The other V-6 was replaced BEFORE I bought the car at 78,555 miles, with a '72 500 installed. One of my V8-6-4's has 190,000 miles and the other 138,000 miles. The '80 368 has 132,000 miles and uses a quart of oil every 1000 miles or so (the engine is over 24 years old and has not been apart except for a water pump and timing chain which was changed as preventative maintenance). Two of the 4100 cars, which I have pulled the 4100's from, are getting 472/500's.

Pat

It looks as though you are correct.
http://100megsfree4.com/cadillac/cad1980/cad81d.htm

I guess the 368 was never offered any way except in the V8-6-4 configuration.
It looks like the Buick V6 was the best engine offered.

Well I'm really getting an education on my V8-6-4 motor here!

I too have been through too darn many of those piece of crap HT4100 4.1 Garbage motors. I getting sick just thinking about it. :vomit:

My 368 is still under 100,000 original miles and I'm very happy to hear that it's not so much of a TIME BOMB.

Never had the diesel or the V6, probibly cause there all in the junk yard.

PS: I've yet to see a 4.1 make it over 132,000 miles.
if there's one out there, put it in a museum,
It may be the only one worth saving!
But I won't pay to see it!

Of all the cars I have owned, I bought the manual for my '81 V8-6-4's and no other cars. The V8-6-4 was the first car to offer on board diagnostics, and you are right about the scanning ability for things such as:
Throttle position (in degrees; 0 to 31)
ECT Engine Coolant Temperature (degrees Celcius-the sensor signal is also used for the amber "Coolant Temp Light"; because of this, the engine additionally has a "engine metal temperature switch" that gives a red "Stop Engine Temp" light when the back of the driver's side head gets to 380 degrees)
MAT Manifold Air Temperature (both it and the ECT measure from -40 to 150 degrees Celcius)
MAP Manifold Absolute Pressure (in kPa or kilopascals)
BAP Barametric Absolute Pressure (atmospheric pressure; in kilopascals)
Engine Timing (up to 52 degrees; not counting initial)
Injector Pulse Width (from 0 to 99 milliseconds)
O2 sensor voltage (0 to .99 volt)
Electrical system voltage (0 to 19.9 volts)
Open/Closed Indicator-0 for open loop and 1 for closed loop
Number of key cycles since a fault occured; after 20 cycles with no malfunction, it is reset to 0 and all codes are cleared
Additionally, the "switch test" function can be used to test the following:
Cruise control brake switch
throttle switch
drive switch
reverse switch
cruise control dash switch
cruise control "set/coast" button
cruise control "resume/acceleration" switch
"instant/average" button on the MPG display
the ECM's ability to recognize the A/C clutch signal





Pat

Stop it Kevin, you're makin' me blush...

Another thing about the 81's that I forgot about that is really great.

The on-board diagnostics on these cars was actually VERY useful. Unllike the current Fleetwood systems which give information only, the system on the 81 would allow you to scan multiple systems and see values for things like temps, injector pulse widths, timing, etc. It also had ways of testing every underhood switch, selenoid, sensor, etc. from inside the car. It made working on the car a real dream.

Of course to make use of these things, you will have to purchase a REAL GM service manual for it, but trust me, it is worth every penny.

Night Wolf,
Although only rated at 140 hp @3800 rpm, the engine is also rated at 275 ft.lbs. at a very low 1600 rpm. Additionally, these are "net" ratings. The "gross" ratings are about 25% more.

Pat

according to what I just read, the V8-6-4 feature seems real god and cool...... V8 power when ya need at, but cruise on the highway and get 32mpg....... why was there soo many problems with it?

the 368 seems to be underpowered though, 160hp?

seperate question, between the 425 and 500, which is better?

say if you got a '77 CDV and you wanted to make a big sleeper, keep the 425 and build it up, or swap in a 500 and build it up?

Thanks for the timely post, Bill! I've always been intrigued with the V864 engine - always thinking it was a bit ahead of its time (I'm a bit of a computer buff, anyhow) - and today I finally got my chance - an 81 Fleetwood with the V864 engine I found (locally) on Ebay still in original condition. It runs nice and smooth, but I think someone has disabled the system, as the MPG Sentinel always displays 8 cylinders on its screen, even though I might be coasting down a hill at 55+ MPH. There is no Check Engine lamp and no diagnostic codes on the ECC while in diag. mode. I shall try jacking her up on the driver's side and looking for the wire connector at the transmission you mentioned. Is there any other way of disabling the system? It appears that all 4 sets of wires on top of the cylinder heads are in place.

I heard that the system could be disabled, pretty easily, for those timid about the 6 & 4 operation. I would sure love to try the system in all its glory, and then decide whether I want to leave it permanently in V8 mode.

Doug

Congradulations Fleetwood96

on your new perchase. I love mine, hope you'll like yours.

I am having a delema however. I bought a running 500 caddy motor and trans from a friend of mine, I was able to get for $200. I'm tempted to put them in my 81 after I rebuild them, but there's really nothing wrong with my 368 V8-6-4.
It runs great! it only has 87,000 miles on it.

so maybe I'll just hold on to them for now (in storage) and wait to see if I can find a really nice Fleetwood or Coupe Deville body with a blown HT 4100 in it for cheap!

But then I will have two Caddy's, parking is a problem, and I really don't want to give up my 81, or the new motor. I'm adraid that if I end up with two I'll be tempted to sell one. ( I sold my house and have limited parking now)

I still have my 91 mustang stored at a friends house, My 83 sedan Deville I let my stepson drive it, cause I have no place to park it. (it's for sale)
Then my wifes car, and my daily clunker (nissan).
so that's 5 cars already, damn I kinda miss having a yard to park them in!

Someone correct me if I'm wrong but.......don't the 368 and the 4-6-8 (8-6-4) use the same block? It was the electronics that made them different, right?
If memory serves, you are correct, the Valve covers are the only difference I believe.

I'll be getting another car soon and theres a 81 coupe deville for sale. Anyone know what it has under the hood? I hope its not a 4.1.
The 1981 Cadillac shop manual lists the 4.1 six cly. engine, 368 4, 6, 8 engine, and a 368 block diesel.

this has enlighten me about the V8-6-4