Cadillac V-8-6-4

[dennis in se pa]

Back in the 80's. Cadillac/GM had some engine problems with these and their diesel engines. Was it really that bad or in the 8-6-4s could you just turn off the software?Looking at a 1985 Cadillac Biarritz as a classic investment.

[speeder]

It was really that bad. Engineering malpractice. I’d invest in beanie babies or something more practical.

EDIT: Just re-read your post. By 1985, the 8-6-4 was long gone.

[dennis in se pa]

Originally Posted by speeder

It was really that bad. Engineering malpractice. I’d invest in beanie babies or something more practical.

EDIT: Just re-read your post. By 1985, the 8-6-4 was long gone.

I thought it was the last year.

[john walker's workshop]

My 2007 Chevy truck has that. Hope it's better than the caddy system.

[asphaltgambler]

Yes Forest, run........run away quickly. GM has always had some of the greatest ideas and engineering .......on paper. But by the time the accountants and other bureaucracy - you end up with crap like this. Oh and by the way that same setup is in the current LS V8 engines causing all kinds of oil consumption problems.

I can't think of any 1985 domestic vehicle that I would own, unless someone just have it to me in runni,g condition

[asphaltgambler]

^^^John, sorry no its not....

[UconnTim97]

My 2008 GMC with the 5.3 and the cylinder/fuel management system used more oil at 145,000 miles than a 2-cycle engine.

[gizmofixer]

The 8-6-4 was used in 81 for regular production cars (and 82-85 factory limos).
It was a system way ahead of its time really, the only problems were techs that didnt understand how it worked.
The 5.7 diesel was truly a piece of crap, basically a converted 350 gas olds engine. (Avoid them like the plague.)
In an 85 Eldo you would have the HT 4.1 aluminum engine.
This was a woefully underpowered boat anchor. Many serious problems including main bearing knocks and a propensity for eating camshafts/lifters.
Best year for that Eldo body style was 1980 with the 368 engine and fuel injection. This engine was an underbored 472, the best old-time good-forever Caddy engine ever built.
As a Caddy tech for over 30 years, feel free to ask me anything about them!

[jcommin]

Originally Posted by gizmofixer

The 8-6-4 was used in 81 for regular production cars (and 82-85 factory limos).
It was a system way ahead of its time really, the only problems were techs that didnt understand how it worked.
The 5.7 diesel was truly a piece of crap, basically a converted 350 gas olds engine. (Avoid them like the plague.)
In an 85 Eldo you would have the HT 4.1 aluminum engine.
This was a woefully underpowered boat anchor. Many serious problems including main bearing knocks and a propensity for eating camshafts/lifters.
Best year for that Eldo body style was 1980 with the 368 engine and fuel injection. This engine was an underbored 472, the best old-time good-forever Caddy engine ever built.
As a Caddy tech for over 30 years, feel free to ask me anything about them!

Yep! The diesel was a piece of crap. Cylinder deactivation is quite common today. Even the Wright Brothers didn't build a 747 the very first time.

[mreid]

It was originally called DOD (displacement on demand) and it was horrible. It was reengineered and reintroduced as AFM (active fuel management). It still has problems and while GM has not admitted it has problems and continues to blame consumers for not changing oil or using the wrong oil, they just recently introduced a new replacement (new boss same as the old boss) called DFM (dynamic fuel management). I’m not holding out hope.

The 2012 Camaro engine I put in my 1988 Land Rover has both AFM and VVT. I had AFM turned off in the ecu, but the hardware is still on the engine. So far, so good and I’ve been told that as long as it wasn’t causing a problem before (engine only had 20k miles) I should be good. Goes like stink right now with no issues and I hope it stays that way.

[MRM]

Weren't the GM diesels of that era so bad that they are credited with turning America away from diesel engines entirely?

[fastfredracing]

Originally Posted by gizmofixer

The 8-6-4 was used in 81 for regular production cars (and 82-85 factory limos).
It was a system way ahead of its time really, the only problems were techs that didnt understand how it worked.
The 5.7 diesel was truly a piece of crap, basically a converted 350 gas olds engine. (Avoid them like the plague.)
In an 85 Eldo you would have the HT 4.1 aluminum engine.
This was a woefully underpowered boat anchor. Many serious problems including main bearing knocks and a propensity for eating camshafts/lifters.
Best year for that Eldo body style was 1980 with the 368 engine and fuel injection. This engine was an underbored 472, the best old-time good-forever Caddy engine ever built.
As a Caddy tech for over 30 years, feel free to ask me anything about them!

I was thinking 4.1 . Dad had a couple, on one, the cam was out at 35000 miles, and it always knocked. The other made it to 60k miles, what an awful powerplant.

[Scott R]

I didn't see anyone answer your question, but yes you can just disable it and it runs on 8 cylinders all of the time. In fact we never really fixed these at the dealer due to cost of the repair, we just disabled them when the customers brought them in with issues. This was in the early 90's so I never worked on them under warranty however.

[gizmofixer]

To disable the 8-6-4 we would fool the ECM by giving it a 'no 3rd gear' input signal.
In my opinion these Eldos (79-85) especially the Biarritz, are beautiful, great riding cars but will NEVER be a good investment.
I struggled for 2 years to sell my 80 Biarritz in mint showroom condition.
I paid 6k for it in 1984 and sold it for 6k in 2015

[berettafan]

Originally Posted by john walker's workshop

My 2007 Chevy truck has that. Hope it's better than the caddy system.

not really.

google 'Chevy AFM problems'

literally thousands of pages of threads bemoaning this 'feature'.

my '13 Suburban drank almost 2 quarts in 7k miles. had 50k on the clock.

[nota]

the 4.9 drops in the 4.1 spot and is a lot better motor
if one has to have a 85 eldo

the 4.9 is favorite swap in to a fiero a fairly eazy swap

[beepbeep]

Originally Posted by gizmofixer

The 5.7 diesel was truly a piece of crap, basically a converted 350 gas olds engine. (Avoid them like the plague.)

As far as I read, it was actually built from scratch as diesel engine. Block was/is much sturdier than 351 gas engine but they missed two important things:

1. head bolts were too weak and too few so heads "walked" around under hi compression.
2. No water separator in fuel line = rusted pumps = carnage


...and they were completely gutless as well. Like 85hp or something.

[legion]

Originally Posted by asphaltgambler

Oh and by the way that same setup is in the current LS V8 engines causing all kinds of oil consumption problems.

I have a 2007 (new body style) Chevy Silverado with the 5.3 that I bought new.

I've never had oil consumption issues, except for the year that I lived in Atlanta. 45 miles a day commuting in stop and go traffic. I put 20,000 that year on the truck, whereas a typical year I put on my like 8,000 and never really sit in traffic.

The problem magically went away after I moved.

[speeder]

Originally Posted by MRM

Weren't the GM diesels of that era so bad that they are credited with turning America away from diesel engines entirely?

That is said quite a bit but Americans were never fans of diesel powered vehicles to start with. You have to remember that all diesels were indirect injection and not turbocharged in those days, so slow as can be even if they were reliable, (such as Mercedes-Benz).

The late-'70s GM diesels really helped to kill whatever small interest there was in them here but no one really wanted them in the first place. Even if they had been bullet-proof, they would not have caught on with their anemic performance and noisy, smoky character. VW was also selling diesel Rabbits and Jettas around that time that would lose a race to an athlete on a ten-speed bicycle.

Originally Posted by beepbeep

As far as I read, it was actually built from scratch as diesel engine. Block was/is much sturdier than 351 gas engine but they missed two important things:

1. head bolts were too weak and too few so heads "walked" around under hi compression.
2. No water separator in fuel line = rusted pumps = carnage


...and they were completely gutless as well. Like 85hp or something.

I have fond memories of riding in my best friend's family Cadillac diesel w his mom driving, in the meter line of onramp to Highway 62/Crosstown in Minneapolis. Everytime one car would go through the light, she would stomp the accelerator pedal to the floor to move 20' and then stomp the brake like she was driving a golf cart. Good times.

Domestic automakers were really struggling to come up w fuel efficient solutions in those days.

[legion]

Originally Posted by speeder

You have to remember that all diesels were indirect injection and not turbocharged in those days, so slow as can be even if they were reliable, (such as Mercedes-Benz).

...

I have fond memories of riding in my best friend's family Cadillac diesel w his mom driving, in the meter line of onramp to Highway 62/Crosstown in Minneapolis. Everytime one car would go through the light, she would stomp the accelerator pedal to the floor to move 20' and then stomp the brake like she was driving a golf cart. Good times.

I had a 1985 MB 300D in college. Pulling away from any intersection involved mashing the pedal to the floor just to get rolling, then strategically lifting off the accelerator as the turbo came up to speed. I swear that car had a 0-40 of like 20 seconds and a 40-70 of like 3 seconds. So it took forever to get up to speed but getting to the right speed was very difficult. Because of this, the brakes often had to be used quite aggressively.