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As I recall, regular Jeeps left the flat head engines when they left the flat hoods to cover them.. I don't know what civilians called them beyond CJ2 for the flat head model. In the Army it was the difference between M38 and M38A1.
Those later 4 cyl engines were called F-head engines,4 valves in the head and 4 valves in the block. Externally, looked like an OHV engine.
I always liked Jeeps, but I got ripped on one new one, I bought in 1978. I think it was because it was built
by AMC, just as they were about to quit business.
It had the bigger 6 cyl engine, something like 256 cu in.. No power steering..so many turns lock-to-lock.. if you got in a skid on ice, you couldn't turn thewheel fast enough to recover very well. ..Besides, that heavy engine up front, didn't help it any in 2WD..
First time I put it in 4WD, I found that the transfer was such that you could put it in 4WD..but you could, if not careful, go right through the 4WD notch, and not have complete gear contact.
One day, while cleaning the interior, I discovered the the steering wheel was badly molded..some of the steel hoop inside was showing on the surface of the wheel...just painted to match the black plastic..and let go.
By the time I got rid of it (about 2 years) rust was already peeking through in a couple places.
In1998, I bought a Chrysler made Jeep Wrangler Sport. It had a 4 cyl engine, set well back toward the firewall, it was an excellent vehicle in every way.