Home » Engines Of Varying Displacement: 1981 Cadillac Seville vs 2006 Chrysler 300C

Engines Of Varying Displacement: 1981 Cadillac Seville vs 2006 Chrysler 300C

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On today’s Shitbox Showdown, we’re taking a look at two luxury sedans with V8s that are capable of acting like much smaller engines. One was an unmitigated disaster, and the other, well, the jury’s still out on. But before we pop the hood on those, let’s see how yesterday’s lawn ornaments did:

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Huh. I am surprised, and I’m not sure I agree. The Rodeo would make a fine beater, if you could hop in and drive it away, even if it needed some work. But the idea of resurrecting a non-running early-90s SUV has about as much appeal to me as a day-old Big Mac. I’ll take the Newport, keep the patina, and drop in an engine from a newer Dodge truck.

We all know what we love about V8 engines: the sound, the smoothness, the rush of torque that pushes you back in the seat when you step on the go-pedal. And we all know what their worst attribute is: fuel consumption. But what if you could have a V8 that was only a V8 when it needed to be, and ran on fewer cylinders under light loads to save fuel? Sounds like the best of both worlds, right? Well, GM engineers thought so, twice, and the second time were joined by Chrysler. It’s rarely the case that the sequel is better than the original, but this is definitely one of those cases. But let’s give them both a fair shake, and see what you think.

1981 Cadillac Seville – $2,900

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Engine/drivetrain: 6.o liter overhead valve V8, three-speed automatic, FWD

Location: Bakersfield, CA

Odometer reading: 19,500 miles

Runs/drives? Starts, not drivable

Cadillac’s midsized Seville was completely redesigned for 1980, from an unremarkable four-door sedan based on a Chevy Nova to a bold, dramatic reimagining of a 1930s luxury car. Bill Mitchell’s design featured a “bustleback” trunk and a long hood meant to evoke Cadillac’s glory days of fifty years earlier. But I remember my grandpa giving its design a less flattering appraisal upon first seeing one: “Looks like someone ran over its ass with a steamroller.”

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Powering this bold new styling were bold new engines: Oldsmobile’s utterly miserable 350 cubic inch diesel V8, and for one year only, in 1981, this abject failure: the 368 cubic inch V8-6-4. Throttle body fuel injected and computer controlled, this engine could run on four, six, or all eight cylinders, depending on the throttle input. But the system worked too slowly to keep up with demands, and drivability was appalling. Most V8-6-4s were converted to run in V8 mode all the time, which could apparently be done by cutting one wire, but then you were left with a huge, thirsty V8 that still had no power to speak of. The gutless Buick V6, available as a credit option, might have actually made sense by comparison.

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This Seville, with fewer than 20,000 miles on the odometer, apparently has the cylinder-deactivation system intact. The seller says it starts and runs, but can’t be driven, but I wonder if it’s actually just fine (or as fine as these ever got) and they just don’t know what to expect of it. The common complaint of these was a lag when switching back to eight-cylinder operation, making the car sluggish and feel like it’s misfiring. Of course, there may be something more serious wrong with it.

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Wonky engine aside, the rest of it looks like you’d expect from a malaise-era Cadillac with almost no miles on it: clean, but sloppy-looking. Build quality was merely a suggestion in the early Reagan years, but that was hardly a problem unique to Cadillac. These bustlebacks were never my cup of tea, but I know they have their fans, and this one is about as clean as I’ve seen in a long time. You could bolt in any Buick-Olds-Pontiac-Cadillac bellhousing pattern V8, leave the “MPG Sentinel” in the dash as a conversation piece, and cruise around in… well, I guess you could call it style.

2006 Chrysler 300C – $4,000

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Engine/drivetrain: 5.7 liter overhead valve V8, five-speed automatic, RWD

Location: Lake Oswego, OR

Odometer reading: 161,000 miles

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Runs/drives? Just fine

This car, I’m a lot more familiar with. I drive a newer version of it every day, same color, in fact. Chrysler’s LX platform is arguably the best thing to come out of the ill-fated “merger of equals” with Daimler. A large, comfortable rear-wheel-drive sedan was just what the Mopar faithful needed to forget the “nothing but K-cars” era. And the fact that it has lasted for nineteen model years and will be sorely missed when it goes away only drives home the fact that this is one car that Chrysler, in its many guises, got right. The Hemi V8 is, of course, a big part of that success.

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This 5.7 liter version of the V8 with the famous name features its own cylinder-deactivation system. Chrysler skips the six-cylinder mode and goes straight from eight cylinders to four, deactivating cylinders 1, 4, 6, and 7 at steady speeds. Advances in computer technology have eliminated the lag, and the Chrysler system works by collapsing the hydraulic lifters instead of disconnecting rocker arms, making for a simpler mechanical system. It’s generally a reliable and durable system, but there are reports of failures, usually caused by neglecting oil changes or using the wrong viscosity oil, resulting in bent pushrods and wiped cam lobes. You can turn the system off by putting the transmission in “Sport” mode, but it reverts to normal when you turn off the ignition. A more permanent disabling involves replacing the camshaft, lifters, and some other things.

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This 300 runs great, and has had some recent service including a fluid change to its Mercedes-sourced five-speed automatic transmission. Everything works except the display screen on the infotainment system; fortunately there are buttons and knobs for everything, but setting radio stations might be a bit of a crapshoot.

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Otherwise, it looks like it’s in good condition, and a hell of a lot of car for four grand, actually. And the fact that this one is in such good shape after 161,000 miles makes me optimistic about the future of mine. These are a great way to enjoy a Hemi without the boy-racer stigma surrounding the Dodge Charger and Challenger.

V8 engines have been a cherished part of the automotive landscape for more than a century now, but they’ve never been the most thrifty option. It’s a bit irritating that, now towards the end of their run, the multiple-displacement method of making them more fuel efficient has actually started to work, but better late than never, I suppose. You can either take the museum-piece 1980s version try to make it work, or just go for the ready-made 2000s version. What’ll it be?

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(Image credits: Craigslist sellers)

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Racecar_Steve
Racecar_Steve
10 months ago

Hmmm… The condition of that Cadillac makes my spidey senses tingle… Having owned an 80’s Cadillac (’89 Deville), the general condition of that car, while not terrible, still seems more in line of a car with 120k miles, not 20k (Various upholstery tears, degraded seals, etc.). Also, the seller’s comment about “Engine needs repair/rebuild/replacement […] Car starts, but
is not drivable” raises all the red flags for me as this not simply being
an issue of a car that drives a little bit “off” because of the
V8-6-4 system.

On top of it all, I find the bustle back Sevilles to be one of Cadillac’s most unappealing designs of the era, so I guess that pushes me to the Chrysler 300 by default.

Justin Short
Justin Short
10 months ago
Reply to  Racecar_Steve

In the ad it does say odometer rolled over

Racecar_Steve
Racecar_Steve
10 months ago
Reply to  Justin Short

ah- good catch. I missed that over on the side of the ad. That makes much more sense.

Mr Sarcastic
Mr Sarcastic
10 months ago

I bet from your comments i can tell your puck.

Slow Joe Crow
Slow Joe Crow
10 months ago

300, because I dislike the bustle back Seville and loathe the V8-6-4 and HT4100

RataTejas
RataTejas
10 months ago

I voted Seville. Of course I owned a 71 Coupe deVille, so this is more of a compact.

Tim Beamer
Tim Beamer
10 months ago

Had the same engine in my ’06 Charger Daytona R/T. Regularly got ~27 MPG on the interstates.

PaysOutAllNight
PaysOutAllNight
10 months ago

I’m all for a Chrysler 300 Hemi. They’re high on my list of “want to own” cars. They’re great for eating up the long miles, or hooning around in general without looking like it.

This one is definitely cheap for what you get, assuming it checks out as presented. I’d rather have a later model with the awesome ZF licensed 8 speed transmission, but the Mercedes derived 5 speed is plenty durable and does the job nicely.

The Cadillac? No interest whatsoever. Not even as a “classic” cruiser. There’s nothing at all special about it, other than the oddly chopped trunk.

If I get a malaise-era luxobarge, it definitely won’t be a non-running V8-6-4 no matter how cheap the price. I”d probably find a square-bodied, B-platform Olds Delta 88 or similar.

Dennis Birtcher
Dennis Birtcher
10 months ago

I’d go for the Cadillac if only to satisfy my curiosity. My understanding is the 8-6-4 is mechanically sound and the problem was insufficient processing power. So what if someone threw, say, a Holley Terminator at it? Four decades of Moore’s Law at work ought to provide exponentially more grunt than required.

The 300 does nothing for me. At least the Caddy I can experiment with.

Speedway Sammy
Speedway Sammy
10 months ago

Or if you’re more ambitious, throw in a 6 liter LS with a 6 speed auto out of a pickup (assuming the trans fits the tunnel).

Dennis Birtcher
Dennis Birtcher
10 months ago
Reply to  Speedway Sammy

If I was putting my money where my stupid ideas are, I’d hold out for a Coupe DeVille, which is both rear wheel drive and not a bustle back. That way, if things go awry, the LS/modern transmission swap is easier. This front drive Seville only interests me in scientific sense, which, again, is still more than than I can say for the 300

Bongo Friendee Harvey Park
Bongo Friendee Harvey Park
10 months ago
Reply to  Speedway Sammy

Or if you’re less ambitious, drive something else altogether. Anything, really.

Kevin B
Kevin B
10 months ago
Reply to  Speedway Sammy

This Seville is FWD.

Mr Sarcastic
Mr Sarcastic
10 months ago

I read GM knew the 8-6-4 was unworkable trash before it went into production. But promises, marketing and spent money mad the decision to go into production with it just long enough to cover costs.

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