We probably won't ever agree on the best stock inline six (I’ve hear the knight sleeve valve was really smooth) but I wonder which was produced the longest? I know Mopar built their flat-head from the start (1924) until the late sixties.
Anyone know a longer one?

By the way I looking at a 1957 Fire truck last week that had a 935 CI Hall-Scott overhead cam 6 in it. 250 HP at 1800 RPM! The same engine was produced by Hudson for marine use.

Leif in San Rafael (I got a new job and I'm not in Oakland anymore)

Dear Leif;

I think you got it right.

Chevrolet built the 216 from 1937 through 53 and then the 235 through 1962 model year. The 261 was basicaly the same (but in trucks/buses) and lasted till 1962 also.

I think the (7 main) style began with the 63 model year & went till the Vortec came to be.

Happy trails.

Whoa fellers...not so fast. You didn't say whether this question was exclusively for gasoline engines or not.

While it does not have spark plugs, the 6-71 Detroit inline diesel engine went into service in 1938 and was produced over 60 years.

If you can hear it before you see it, and there is a large black puddle under it when parked, it's probably a Detroit Diesel!

I have been told that detroits are not supposed to leak; leaks are due to poor air box maintenance. If you haven't ever heard what a detroit diesel sounds like, do a search on youtube for "detroit diesel". There are two videos of a straight piped red grain truck.

I didn't think of that, I think it also gets extra credit for being a two stroke. Excellent!
Duesenburg had some 2 stroke inline 8's in the 1924 indy 500. Too bad none survive, I bet they made quite a sound!
I was in the Army circa 1970 and we had this thing called the "gamma goat" which had 6 evenly spaced driven wheels and the 3 cyl version of that engine.
It made you deaf.