Q for the old timers (Flat fender fuel mileage)

Did they ever put a flat head six in a Jeep?

For that matter was there ever a flat head four? The F head is only partly a flat head.

It really depends on the engine and the car itself. I used to have a 57 Studebaker wagon with a flat head six, NEAT car but both it an I would have been a lot happier with a Stude 259 V8 in it.

Again, I only have experience with Studebakers but an early Lark with a the six and overdrive will get in the low 20's. You won't win any drag races but it will get you there and will keep up with modern traffic.

There are also things you can do, there is a conversion kit available that enables the use of a more modern 2bbl carburetor and it actually increases both power and gas mileage. Then you can also get performance parts but I suspect that would defeat your purpose... although with that carb conversion, a mild compression increase, and with electronic ignition I bet that same Lark could approach 30 MPG.

To stay on topic I understand that same little Studebaker Champion six is pretty much a direct bolt in replacement for the F head and would give you better performance and possibly better mileage, especially with those upgrades.

Jeff DeWitt

Sim> What kind of mileage could the old small displacment 4 and 6 flatties

By flattie I mean Flat fender Jeep, a Willys MB up to a CJ2a, so what I'm asking is which of the old extremely light weight WWII era Jeeps got the best MPG?

Most old flatheads were very thermally inefficient because of the low compression and the large surface area of the combustion chamber. That's why flatheads were never used as aircraft engines with the exception of the Continental A-40 (which was originally developed as a motorcycle powerplant) and the Funk Ford conversion. Virtually all were replaced with A or c series continentals after WWII.

If you build an inline flattie you will want to fit the block with Stellite exhaust valve seats and an upgraded aftermarket stainless valve for use with modern fuels. Probably the easiest to find today would be a Continental Red Seal out of a welder, genset, pump or forklift as they were made up until five or six years ago.

You have to put an overdrive unit in it to get good fuel mileage, and even then I doubt you'll get out of the low twenties. If you really want to know who got the best WWII gas mileage, it was probably the Kubelwagen, military version of the VW Bug. Think about fuel shortages and blockades, motivation to design an economical vehicle.

My 1995 Wrangler has the four cylinder AMC pushrod engine, modern fuel injection, and five forward speeds. The best I can get out of it is 26 mpg. I think I am limited by aerodynamic drag. I am going to do some top-down tests this summer as soon as it stops raining. :o( If you really want to save fuel, my aerodynamic Honda Civic HX, a model that was specifically designed for increased fuel economy and decreased emissions, gets 40 mpg in the mountains, 45 on the Interstate.

As the resident Studebaker nut pointed out, an "economy car" from that era was probably my uncle's Lark, or the 1960 Rambler American I tried to restore once. After I spent some time reading manuals, looking at the actual design, and pondering the effects that a broken ring will have over time, I traded it in on a 1985 Cavalier station wagon.

Good luck though.

Earle

It weighs close to 4,000 pounds which is roughly 2 times more than a Flat fender.

Fuel economy isn't the be-all end-all goal, I'm just looking for opinions on the best power plant to start with. Assuming it had to achieve highway minimum speeds of 55 to 60 MPH (which to tell the truth is all I ever do in my YJ because of the aerodynamic's problem)

I do of course realize there are better suited Cars for daily driving, that's pretty obviously not the point of my question.

I figure 45-50 mph is where aerodynamic factors become more important than weight. Any of the flat fender vintage engines will sip gas all day long idling or crawling around the farm, but on the highway it is going to suffer decreasing fuel economy until you wonder exactly what was the "be-all end-all goal". I don't get the purpose of this project.

Now Bill had the right idea of what to put in an old Jeep. I wonder how much goatpower that 400 cid engine has? Or you could try a more modern four cylinder, something capable of handling forced induction and a wide rpm range.

Earle

half the wieght is going to have some impact regardless of aerodynamics and again this has got zip to do with the question. which was:

What kind of MPG do old willys engine's get and which of them was best in that regard...

Not "what is your opinion of trying to get good MPG out of a Willys"

Any of the flat fender vintage engines will sip gas all day long

Fun

That was interesting but obviously in French, which makes me wonder did Jeep sell any flat head sixes in the US or were they just for export?

Jeff DeWitt

L.W.(Bill) Hughes III wrote:

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Now is that with, or without, the optional overdrive? ;^)

I wonder if the USPS would have this information, and if they would share it? Postal Jeeps were a lot like real Jeeps, except for a couple hundred pounds less of running gear. Back in the Day, no one cared about mileage, except for the fleet owners.

Earle

Simon, this might be a good place to get started.

Bill,

You could get into a lot of trouble with those "Nash Airliner Reclining Seats that adjust to four positions". ;^)

Earle

And what makes you think that had anything to do with your vehicle?

You should mention to the younger readers that 'highway speed' was 35 mph...