More on an old thread...RPM?

sald

Member
I came across this old thread regarding A's RPM settings. It references serviceman's manuals that say different to my manual. I am just curious as to the logic behind the specs. It seems the general consensuses is 1540 No Load to wind up with 1400 Load. Others state the engine would be set to 1800 at the factory. Were the engines RPM settings based on achieving a specific speed on the PTO? or to save or protect the engine? I am leaving mine at 1540, but really interested in getting the real rational around the settings.

Old Thread:
http://forums.yesterdaystractors.com/ttforum/viewtopic.php?t=797621&sid=fdb2e75813327a60944b3f584fb39160
 
The PTO rpm is pretty important and should stay in the 530 to 560 RPM range under load. Running wide open will push that limit.
SO. If the PTO issue is not a problem, running the engine (In good tune with good oil) at 2100 is not going to blow it up. It is
likely that different years and Super A, SuperA1 Tractors had differing RPM on the ID plate. Jim
 
Cool, so then they were trying to achieve the proper PTO RPM by means of the speed of the engine? It wasn't that the engine was a concern.
 
I'm going to say that directionally, it has to do with the metallurgy in the cylinder head. The exhaust valve can recess into the head due to seat wear if the seat "wears" basically by micro-flaking away. Its not an instant thing but the more "duty cycle" that one puts the engine thru the faster it can happen.

A head with added hardened (steel, not cast) seats, is not an issue, but a head that's cast and then the seats induction hardened faces some issues.

These are generally low powered engines for their displacement, and the tradeoff is that they last a long time. But my opinion is that every incremental step taken into higher power, faster speeds (both lead to more heat) is an incremental step backwards in long term durability.
 
Correct. Early engines were slow. in the 1920s many were 750 rpm. IH found that the 113 123 and 135 engines could work at 2100 pretty much without issue. Materials were improved as time went by and unless your engine is using oil and has oil pressure issues, it will be fine. Jim
 
(quoted from post at 22:01:16 10/14/18) Correct. Early engines were slow. in the 1920s many were 750 rpm. IH found that the 113 123 and 135 engines could work at 2100 pretty much without issue. Materials were improved as time went by and unless your engine is using oil and has oil pressure issues, it will be fine. Jim

My engine is running well. Oil pressure is fine and I just ground and polished the rocker arms so I was able to precisely set them. 100 psi in all 4 cylinders.
I am leaving my settings at 1540. I just wanted to better understand the thought process.
Thank you.
 

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