C-135 horse power

[marc walker]

Is there any way to tell what HP engine I have? I have found a 340 made from 58/63 has a compression ratio of 7.6:1 listed HP 47
The 404 made from 61/68 has a compression ratio of 7.7:1 listed HP 29
My engine block was cast, according to the numbers 3/27/1969.serial #120624. If it was a power unit engine instead of a tractor engine would it have any extra markings anywhere? like maybe a uc-135 instead of c-135. Thanks as always.

PS cranked her up today she sure sounds hefty through a straight pipe.
 

[pete 23]

I don't know about the markings but the horsepower will be solely dependent on the rpm's engine is run at with the carburetor and ignition systems that match that. A C-135 may well be run at 1600 rpm in one unit and 2000 rpm in a different application.
 

[mkirsch]

Compare apples to apples.

The 47HP number on the 340 comes from the raw engine HP.
The 29HP number on the 404 comes from the PTO on an LP engine.

If you compare the Nebraska tests, the two tractors were nearly identical.

Farmall 404 gasoline - 32.97 drawbar HP
Farmall 340 gasoline - 34.74 drawbar HP

Since the 340 is a physically larger, heavier tractor I am not surprised that it performs slightly better in a drawbar test. The 404 has the lighter "Super C" style rear end vs. the "Farmall 460" style rear end that the 340 has.