: Considering a 1984 Coupe Deville

02-10-09, 09:11 AM
Good Morning all,

I am considering purchasing a 1984 Coupe Deville... It supposedly had its engine replaced 19,000 miles ago. If the body is as good as they say it is (for wisconsin anyways), how much should I expect to pay, depending on mileage?

Should I run from this HT4100 simply because of that? What sort of things should I look for or tests should I put it through when deciding to purchase this car?


02-10-09, 10:10 AM
If it's a good condition car, and if worse comes to worse and the 2nd HT4100 craps out -- would you be willing to replace w/something NOT the HT4100 and keep driving it? That would be the first thing I asked myself.

02-10-09, 10:22 AM
Ask for the receipt for the engine change. If it is rust free, decent paint, and the interior is good, I would pay up to 2000. Rust, ripped up interior, questionable maintenance records... pass.

02-10-09, 10:30 AM
And it depends on the mileage too. If it's 50000 miles, I'd pay a couple thousand more (maybe). If it's 200000, I wouldn't buy it at all.

I'd just prefer a '78 or '79, but that's just me.

02-10-09, 12:19 PM
Was it daily driven in Wisconsin year round? If so.. check the frame and floorboards. After living in the midwest for 2 years I realize how hard it is to find rust free older vehicles.

02-10-09, 03:22 PM
More info...it's got 120,000 miles on it, and the engine was replaced at 103,000 back in 1992 (with a NEW engine, not rebuilt, or so I am told). They do have the paperwork for it showing mileage and amount paid, etc. Since then, it sounds like there has only been 1,000 per year on average driven. Supposedly, it is a two owner car (never know until you carfax though), and they want just under $2,000.

Goin to take a look at it on Saturday, so I should have more info then...

02-10-09, 04:17 PM
Can you verify that it is only 120k miles and not 220k miles? These cars only have odometers that go up to 99,999 miles and then roll back to 1. You should be able to tell if it has way more miles than they claim. If replaced with a new engine in '92 I would take it. Cadillac fixed almost all issues on the 4100 by the 1987 model year. As for the rust it might not be that bad. Some parts of Wisconsin use sand instead of salt which is far less corrosive to a car's body.

02-10-09, 06:00 PM
Well, if it turns out that I should be serious about this car, I'd definitely do a carfax to ensure it is only 120,000. I have found that mileage CAN be deceiving though (I have a 78,000k Deville that is just going straight to hell, but had a Deville with 215,000 with slightly LESS issues)... Maybe this is getting into something that only someone on the inside would know, but is there a way to tell the which version/ year of a HT4100 this particular engine would be? I mean, whoever put this new engine could have purchased it back in 1984, but since it was never used, they'd still say it's new...and technically, they'd be correct...

How difficult (if it came down to it eventually) would it be to swap for the 4.9?

02-10-09, 06:36 PM
I bet the 4.9 would be hard due to the RWD v. FWD.....but others would know more than me. I would think the engines later used in the Brougham would be the easier swap.

02-10-09, 11:14 PM
Switching to the 4.9 would suck. It can be made into rear wheel drive as there is someone on my Isuzu forums that has one in his Rodeo (how bad ass is that!). You would also have to switch over all the electronics and the 4.9 is also port injected, not throttle body injected so you may have to change the fuel pump and lines as well as they run much higher pressure through port injected systems.

02-10-09, 11:46 PM
The 4.9 makes similar horsepower and torque numbers to the TBI 5.7, and it's gonna be a lot more complicated to put the 4.9 in, versus the 5.7, so I'd just as rather do the 5.7. But in all honesty, I'd put a big block Cadillac engine in if I was gonna do a swap.

02-11-09, 11:36 AM
I guess to be honest, I'd rather not even think of the possibility of a swap, but I'm sure its possible...

Any idea how to tell which version of the HT4100 was put in?

02-11-09, 07:57 PM
Any idea how to tell which version of the HT4100 was put in?

The amount of antifreeze under the car! :rimshot:

02-11-09, 09:39 PM
Any idea how to tell which version of the HT4100 was put in?

Get under the car, and look at the side of the engine block, halfway up, by the mount. There will be a GM Remanufactured ID plate with the bearing specs on it. That's what's in my mother's 84. Her car developed a bad knock at 55 000, and the dealer installed a "NEW" engine. I only found out years later when I started working on it that it was a rebuild.

02-14-09, 08:40 PM
Those engines seemed to have a lot less problems in those cars then the front wheel drive ones for some reason. If you like the car get it and if the engine dies just put something better in it.