RWD 4 door challenge
 

Hello all. Long time lurker first time poster here. First let let me start off with I understand the limitations. I don't expect 100 or even 50 mpg but I would like to get as much as possible 30-35 would be great. I despise fwd cars and I need 4 door family ability. I prefer classic cars but understand the weight and aero drawbacks. I will work out the drivetrain but am having a tough time choosing a platform. For awhile I was looking for a 62-65 fairlane as they are midsize relitively light and available in 4 door. It's tough to find frontal area and cd figures for classic cars. I would go newer if it were worth it. Thought about 80 ish Malibu maybe a wagon. I even considered an corvair but have pretty much crossed that one off for multiple reasons. Okay I'm ready for all helpful replies.

I think you'll get much better fuel economy out of a more recent engine, at least with EFI (assuming same HP, of course). So newer engine transplant?

I have lots of drivetrain ideas. Everything from Vw tdi to gm 2.8 v6 or roller block 305 with crank out of l99 4.3 v8 making a roller cam 265. I like distributors and carburetor but have built and tuned a mega squirt car as well so I'm not afraid of efi. I will be looking for efficiency on highway out of low end torque and high gearing. Rear axle in the 2.28-2.41 range and t-5 t-56 or 700r4 auto with lock up converter belly pan front air dam drum or small disc brakes probably steel wheels skinny tires. The stock l99 in the mid 90's caprice were good for mid to high 20's in that big heavy car. So I would think a similar engine in a lighter car with belly pan and proper wheel tires and gearing should return low 30's highway. No AC no power steering. Just wanting to start with the best platform to build from.

If its a GM car then it will likely have the 10 bolt 7.5 or 7.62 inch ring and pinion gear.
Then your only options for numerically lower new gears is 2.73 gears or 3.08 gears.
The numerically lowest I am aware of for the 10 bolt was 2.54 gears, but I know of no one that makes them.
The lowest numbered gear I think you would want to have on a car like that is a 2.73:1.

If you go with an older GM car again it will already have some what small brakes up front.

The late 70's Cadillac Seville came stock with 2.28 some say 2.29 rear gears. The gm 7.5 could be had all the way down to a 2.14 that came in some 79 or 80 malibu's there are ford rear that can be had in a 2.41 so tall rear gear won't be to difficult. I will pic rear axle ratios after deciding on engine trans wheel and tire to get the best flat ground cruise rpm at 70-75 in top gear. I'm thinking 1300-1700 rpm range. I am most concerned with highway mileage. That is why I asked about a light but more importantly aero platform to start from. The Malibu are shaped like a brick as are most cars that fit my size and rwd requirements.

For 1 year right at the beginning of gas price increases I bought a 2.29:1 rear out of a Malibu and swapped it in to my Monte Carlo (78-88 g-bodies). I didn't have a way to calculate miles travelled other than the math that I think was correct/close to accurate. I drove for a week at the "math'd out" RPM for 65mph (1600ish) and got terrible mileage; even worse than with the stock 3.73:1 rear. Once I brought the RPM up to 2000, I started getting much better MPG to the tune of ~25mpg around ~80mph.

Cruise RPM is super important and should not be over looked. A t56 with its double overdrive might never see 5th with such a tall rear gear. 6th might be totally useless n

I like the idea of a 4cyl cummin in a Malibu wagon.

I also know sometimes lower rpm can hurt mpg. Especially with a short stroke engine or one with cam that makes peak torque higher in the rpm range. I doubt I will need or want to spring for the cost of a t56. Like I said drivetrain is not what I will have trouble choosing. I was just hoping someone had a platform I had not considered or could give me data on a good choise. Something like believe it or not the 68 caprice despite being a little heavy has a decent aero profile with fast back roof line and at constant highway speed the extra weight won't matter as much as the aerodynamics. So that would be my choice bla bla yadda yadda. Maybe there just isn't a very good platform to start with?

First gen CTS came with an optional 6-spd behind the V6. A competent driver should be able to hit 30mpg without much trouble.

If you are set on an engine swap in an older car, most classics have terrible aero. Look into Land Speed Racing cars for tips on improving them.

Man, I'm in!
You certainly know some stuff!
Admire the thinking outside of the box!
Oh yeah,.....big time welcome!!!

A little on topic
I want to restore a 66 mustang with a bolt in rack-n-pinion suspension, a 200 straight 6 w/ a modified head to take efi, and a automatic overdrive tranny.

First I appreciate the cts suggestion. Never considered one of those and it does meet the criteria
. Not as much fun as building something but definitely the most affordable way to get what I was asking for. I just looked at a few and I might just have to own one of those.

Now to the person with the mustang. Have you seen classics inline alloy head with removable intake for the ford small six? If not check it out. Also check out fordsix forum. If it were me I would look for a 250 inline six with the Windsor trans bolt pattern and put the alloy head on it with an ford AOD trans out of a late 80'S ford Lincoln mercury behind it and do either megasquirt Chevy tbi or fast efi for injection.

Do you have a source for these uncommon numerically low gear sets?
Knowing they exist and having a set in your possession are two totally different things.

I had a hard enough time finding 3.21 gears for my 14 bolt 10.5'' full float rear, then when I found them I had to pay nearly double what all the other gear sets cost because only one company had bothered to make them.

I would either look for a car with them Already in it like if I went Malibu or if it's an axle swap car-part.com is a junkyard search engine and I have located plenty of the 2.28/2.29 cadillac rearends and a few of the 2.41ford rear axles as well. I could have either that I want about anytime I want for 2-300 complete disc or drum to drum.

How much is shipping?
I have never shipped an axle, but I know they ship freight and that's never cheap.

Hard to find for trucks... but fairly common in car differentials.

Reminds me of a local guy that built a '66 with a 2.3T dubbed the GT140T:
http://i259.photobucket.com/albums/h...CN16481548.jpg

I see it at some of our local car shows. I believe he claimed 300hp and 28mpg. 600+ pics of the build here:
Brian Fitting's Library | Photobucket

No need to ship as there were some to be had local. But if you had to ship axle freight I would expect to add 150-300 to the price. I would find something within driving distance and just pick it up though. I guess I'll just keep looking for a deal on something that catches my eye and do what I can and see what I can get out of it.

How about a Crown Vic?

I get surprisingly decent mileage from mine and this guy does even better with his:


http://ecomodder.com/forum/showthrea...ank-23057.html

Ha I have driven crown Vic and grand marquis for years for that very reason. One of my favorite cars. I have been considering doing a manual trans swap on one of those for some time. Fairly aero but weak door panels and Windows have various trouble but I still love the panther. Before needing 4 doors I drove mark viii and regularly saw 30 mpg.

The towncar, vic, and marquis drink fuel in town almost as bad as some SUVs.
We had one for a while.

2000 Lincon Town car Gas Mileage (Towncab) - EcoModder.com

True the panthers do get a little thirsty in town. My main mialage concerns are highway mpg's as I do lots of interstate driving and very little in town.

A good point for the Crown Vic is that its body-on-frame layout leaves more room for some extreme mods. For example, what about a custom aerodynamically-enhanced single-piece front clip? Or a kammback? And with regard to powertrains, nearly every configuration is possible. What about the V6 bolted to the manual transmission of a base model F-150?

Still they are heavy and I'm a touch bored with them. I would much prefer a 4 door 62-64 fairlane nova maybe Amc rambler or the like to start with. Rear wheel skirts belly pan Cummins 4bt 5 speed and high rear end gears.

Never mind the 4bt I forgot how pricy those things are.

If you want a classic GM car, I would suggest a 1959-1970 Chevrolet full size car or something similar from another GM division. The transmission could be the 700R4 four speed automatic. The engine could a 283, 307, 327, 350 or 305. You can increase the compression ratio to about 10:1 and install an aftermarket camshaft for a turbocharged engine which has about 10 degrees more duration on the intake lobe. That will make it an atkinson cycle engine at low speed but give extra power at higher speed. You can also try using a thermal barrier coating on the pistons and combustion chambers.

Another possibility is to find a used Mercedes C or E class from the late 1980's or later. They had low wind resistance. If you can forgive the front wheel drive, the Saab 9000 turbo gives a lot of room, quick acceleration and over 40 mpg on the highway.

http://i73.photobucket.com/albums/i2...snh1ihjck.jpeg

What do you all think of the aero qualities of one of those?

very nice!
Not one door ding!!!!

There are skirts for the rear too. The hood could be sectioned or pancaked to improve aero lesining the frontal area without ruining the good looks. Stock curb weight of 3100 pounds is doable. The bulged rear fenders could be removed and the tapered body line continued from front to rear giving even more boat or teardrop shape to it. I would hate to modify the body that much ruining some of the styling but would make it very aero. Tuck a narrowed rear end would almost make it tadpole ish. I wount go that extreme but I think I have settled on the body. Now just how many highway mpg can I build it to achieve?

They LOOK aero...




That's a '49-'52 Chevy Fleetline sedan, right? The only thing I can find on them is an estimated Cd=.65. Not sure if that is accurate, but with a few rare exceptions, those '50s era cars were not designed for aero. The side profile deviates from the aero profile by the middle of the rear door.

It couldn't be that bad could it? Worse than a jeep Cherokee? That is a 1949 Chevy fleetline. For comparison do you have any estimate for 1968 caprice or 1962 fairlane Est Cd figures?

If you get anything '67 or older, thus EPA-exempt, you can slap any other Diesel that might be cheaper. Even those not certified for road vehicles.

Any consensus on the most effecient least expensive diesel that is not rated for road use? That can relitively easily be mated to an automotive transmission?

A few people have used Kubota diesels (used to power Refrigeration units on refer trailers) such as this guy with a Wrangler:
http://ecomodder.com/forum/showthrea...llo-28072.html

Perkins diesels are used sometimes as well.

Yanmar TNV-series engines are also an option. But if you were mind-set on Cummins, there is the B3.3 which was co-developed with Komatsu and is lighter than the B3.9 altough not certified for automobile applications. Electronically-governed QSB3.3 has been used in Toyota Tacoma and J70 mining trucks.

Makes me wonder how this one would fare aerodynamically-wise
http://automovelbrasil.com/assets/i/...bc37344c28.jpg
http://automovelbrasil.com/assets/i/...33bd7f27c5.jpg

I would go for an early 80's Caprice and get an L05 350 with 700r4 and 3.08 gear. It's a good combo for the highway. Put a belly pan on it and lotsa room for mods...

6.2 or 6.5 NA in a caprice/impala ss w/700r4

The cts is nice, i love mine. But he aero isn't very good. 90% of my driving since 6/1 has been straight highway with very few stops, i keep the fuel log fairly up to date in the garage here.

If you want a 4 door with good aero, though not light, the dodge intrepid can fairly easily be swapped to rwd.

https://youtu.be/yi0An09-skE

Good luck trying to find a 4-door Chevette out of Colombia, Venezuela, Argentina, Uruguay, Chile, Ecuador, Bolivia, Paraguay and Peru.


I've already seen some Citroens converted to RWD, one with parts of a Chevrolet Opala (Brazilian equivalent to the Nova) and other reassembled over a VW Beetle frame.

I doubt it will ever come up. :rolleyes:

This '51 Citroën Traction Avant became a Propulsion Arrière :D
http://1.bp.blogspot.com/-vS0TLwUfah...Imagem0773.jpg
http://2.bp.blogspot.com/-C5EIbb_YqI...Imagem0774.jpg

You might know there were import restrictions in Brazil from mid-70's until '90, so it was hard to get replacement parts for old import cars. Sure it would make more sense use a VW Passat B1 (a.k.a. Dasher) transmission with the rotation reversed and the water-cooled VW EA827 engine into a Citroën Traction, but a salvaged Beetle used to be cheap enought to justify all the cut-and-weld required. BTW an uncle of mine had a Simca 8 reassembled over a Beetle frame, and many other French cars such as the Renault 4CV (a.k.a. "hot ass") and a handful of British cars from the years of austerity were repowered with Beetle drivetrains in Brazil during the 70's and 80's.