Modify an old 60s Cadillac for 4 or 6 cyl?

[mavinwy]

I would not go with the 2.8 out of a firebird at any rate....They were either OK or REALLY bad.

I would suggest a buick 231 v-6 (also called the 3.8l) They were used to power full sized Le-sabres and Centuries in the 70's and actually did so pretty well. Additionally, if you get a BOP transmission in the caddy, it would bolt in.

I had a '76 Century 4 door with the 231 and got 18 around town and 30 on the highway. This was WAY before I had ever thought about worrying about fuel economy or modding a vehicle for it...so it was mostly stock. It was a great car until the tranny went out. A 60's Caddy would be a little heavier....but likely still driveable.

The motor is known for it's longevity as well...and if you really want to get silly with power, it is the same motor that was used in the 80's for the Grand National with the turbo

Jim

[amcpacer]

I wonder how much heavier the 60s caddy would be compared to your buick. 30MPG is actually quite acceptable for a big car.

[Andyman]

Originally Posted by amcpacer

I wonder what the weight and drag coefficient of an old say 65 fleetwood would be. I have always wanted a luxury car but cannot afford to fuel a 500 cubic inch V8.

I would guess the weight is about 4500 lb. and the drag coefficient is about 0.45. Good tires are important to reduce rolling resistance. Maybe you can reduce wind resistance with some modifications in the grill area.

A modern overdrive transmission will help a lot for highway fuel economy if you use a V8 engine. A good camshaft will also help. A single pattern camshaft (same duration intake and exhaust) like the Isky 256 Supercam should work well. I don't think they have one for a Cadillac but they do have them for other GM V8 and V6 engines.

http://www.iskycams.com/pdfcatalog/2004-05/page62.pdf

[aerohead]

Originally Posted by amcpacer

That is an idea. Just keep the V8 and convert it to propane. I am interested in getting this car: 1967 Cadillac Fleetwood Brougham

I wonder what the cost to operate the vehicle would be on propane compared to gasoline. Also driving range would be an issue if say I take a trip across the USA and need to find places that sell propane only. Ill bet that cadillac only gets 9mpg on gasoline. Probably would need a giant propane tank to tow behind the car kind of like the space shuttles booster rockets.

amcpacer,would the present owner let you burn a tank full of fuel on a test drive? That way you'd know before you purchased.Also,if your going to do mostly highway travel,the smaller engine won't save you more than an mpg according to mid-1970s research.------------------- In the city,a smaller engine could actually lower your mpg as it would be under high load all the time,accelerating such a large mass.------------------------ Early 70s Buick Electra 225,with 455 cu in engine could do 21mpg,the Caddy might be good for high teens,maybe 20.

[Clev]

My friend had a '69 Eldorado with the 472 V8 and 3-speed auto. Curb weight was about 4,680 pounds, and it got about 16 mpg highway. That car had a big Rochester 4-barrel carb and about 10 miles of vacuum hose. It also was massively overpowered: huge battery, huge starter, huge A/C compressor, huge radiator, huge transmission with a chain drive to convert the longitudinally mounted engine to front wheel drive, huge alternator, huge spare tire, 21 gallon tank, huge exhaust system, tons of smog equipment...

If you could get an injected 3.0L or 3.8L, either with a 4-speed with lockup, or a 5-speed stick, you could probably shave a thousand pounds off just the drivetrain, A/C and fuel system and bump your mileage by 60%. Plus you'd have room to store a pair of motorcycles in the engine compartment. I also love the idea of an electric drive with a small engine/generator (3 cylinder Metro motor?) for more range. Oh, and dump those bias-ply tires for some decent radials.

[fud2468]

My old Kelley Blue Book only goes back to 1973 and the 1973 Cad models averaged about 5000 lb. then.The 1976 Century 4D is given as 4017 lb., quite a difference.
The 1965-67 Cad had a 429 engine with 10.5 C.R., '68-'69 had a 472 with 10.0, and the 500 engine became an option in 1970.
C.R.on both the 472 and the 500 was dropped to 8.5 in 1971.
Hot Rod mag did a junk yard Cad engine project a few years ago and IIRC, raised the 500 C.R. to about 12.5 by putting 472 heads on it. That might give good FE with propane and an OD transmission.
Ray Mac.

[mavinwy]

Remember that a good portion of the weight is in the Big Block engine. They are around 500lbs heavier than the v-6. Fud lists the weights he found, and to be honest it pretty well jives with my somewhat rusty memory of the weights of these things.

My century also only had the 3 speed auto transmission. A well built 4-speed would do better on the highway. Once you get the mass of the vehicle going, it actually takes very little HP to keep it up.

It does not sound like you are planning to get rid of your metro either, so this would be a second car? If so, then even if it does not get the best MPG, so be it.

[Jeece]

Go diesel! A pick-up truck diesel engine is designed to toss heavier loads around and still get great fuel economy (compared to gassers). I'm not knowledgable enough to hint at a particular brand though, but I think the idea is worth thinking about it and develop some more.

[amcpacer]

Now that is an idea. The eldorado is front wheel drive! A 3.5V6 from a dodge intrepid has lots of power. Perhaps the GM 3.8 front wheel drive in the 90s regals would have even more power although I am not sure which engine is most efficient.

I think the swift 1.0, a nice comfortable hotel, and some extra spending money would be better than a comfortable car and no money for a hotel on a long trip. You certainly can not beat the coolness factor of a big old cadillac!

[mavinwy]

Actually, the GM 3.8 is the Buick 231. Same motor.
They came carburated, so the swap would be relatively easy. There is also a large aftermarket for them.

Retro-fitting a dodge engine would likely be problematic, but of course...anything is possible if you throw enough money at it, but I don't think changing to another manufacturers engine would pay for itself.

Chenging engines is also generally easier on a RWD car, even if you have to change the motor and trasmission, a custom driveshaft can be built to mate up to the rear end.

Jim