Flatheads not obsolete anymore?

You guys have probably seen me posting lately about my Kohler 6.5 KW generator with the L600 4 cylinder flathead engine. They built that engine up until 1985. I posted the question to YT'ers as to your opinion on why Kohler would continue building what many would consider an obsolete engine. I appreciate the replies.

Well, I got to doing a lot of research on flathead engines and what I learned is that for lower RPM engines (1800 in the case of a generator), that the flathead engine does not really have any drawbacks, except not-so-great emissions.

It appears that old is new again.
A company has been developing a flathead airplane engine. The latest is the D-Motor LF26. 2.7 litres, (165 cubic inches), 88 HP, flat four, water cooled engine. 8.1 compression ratio and burns 91 octane pump gas.

https://en.m.wikipedia.org/wiki/D-Motor_LF26

From Wikipedia:

"This direct-drive aero-engine is unusual in two respects: it is very oversquarewith a bore:stroke ratio of 1.295:1, and it has a side-valve (flathead) valvetrain. The designer determined that since maximum continuous power output (65.3 kW[3]) was to be developed at only 2800 rpm, the extra weight and complexity of overhead valves (OHV)would be superfluous."


They claim that at lower RPM (2,800) that there is no advantage to overhead valves, and that the flathead design has several advantages, some of those being simplicity, lower parts count, and that a valve failure does not take the engine down. They claim that their combustion chamber design with its "squish effect" gives very complete combusion at the RPM level it runs. I am guessing that the electronic fuel injection helps tremendously over carburetion.

4 cyliner version: https://youtu.be/WOD2Us4rtn8

To keep this tractor related, how about fuel injecting old flathead engines? I see where someone is building kits for 4020's. Maybe 8Ns are next.

Interesting!! General and commercial aviation are generally exempt from radical emissions control. Beyond that, it sure is compact and tidy. Jim

Interesting, BTM.

Who'd a thunk it?

Dean

I don't ever remember hearing a smoother running engine that the old Ford V8 flatheads. The Continental 162 (Flathead 4 cyl)powering my Lincoln Pipeliner welder came close...

I learned how to turn wrenches when I was in the 7th/8th grade with my first car, a 1947 Pontiac with 239 CI side valve six. I did a valve job on it when I was 11 or twelve. It took me about two weeks and it did not need it but it was a great learning experience. The Pontiac and Oldsmobile flathead 6's (and 8s) were also VERY smooth running engines.

FWIW, I remember starting the 6V, 47 in in January of 1961 when the temperature was about -28F. Yes, my Father had taught me how to do it and he knew what he was doing.

Dean

It seems they optimized on package width, hence the oversquare bore/stroke ratio and the flathead design. Use of liquid cooling probably helps make up for the poor volumetric efficiency of the L-head.

Experimental and light-sport aircraft have a lot of engine choices, but the vast majority are flat-four, overhead valve, and air cooled. Some are direct-drive, while others use some sort of propeller speed reduction, usually belt drive. In general, they follow the example of the very popular Continental O-200, a 70 year old design.

Kind of reminds me of a Subaru engine, except a flat head, Subaru tried to provide some engines for aircraft, but the neighbors up north bought one for a kit plane and it kept burning pistons, they replaced it with a Lycoming. We sure love our Subaru cars though.

Now dual OHC 4 valve with variable valve timing (chain driven) Also a Subaru Family. Jim

> Kind of reminds me of a Subaru engine, except a flat head, Subaru tried to provide some engines for aircraft, but the neighbors up north bought one for a kit plane and it kept burning pistons, they replaced it with a Lycoming. We sure love our Subaru cars though.

A number of companies have marketed Subaru conversions for experimental aircraft, with varying degrees of success. I think the most successful was Eggenfellner, which went belly-up in the last recession. The price of a Eggenfellner conversion was roughly the same as a new Lycoming, so they had to convince a lot of buyers that they were getting more for their money with the liquid-cooled, fuel-injected Subaru than with a stone-age-simple Lycoming.