Rocker Arm Adjustment

MarlinSlayer · Jun 25, 2015

Well, I changed oil (15W40 as Soundguy recommended) cleaned rocker arm cover, changed breather element in valve housing and oil breather cap. Also changed the plate to a spin on filter. Cleaned at least 30 years of crap out of the thing. Pulled the oilers, shot gum out through them, then pb blaster to get the gumout cleared out of there....then re-installed oilers. Cranked engine with starter and got 20 psi. Did a brief start and got over 60psi then shut it off. Valve train is oiling...coming out the short tube.....so that's good.

I noticed the rubber O-Ring on the end of the long oiler tube was worn and doesn't get a good pressure fit. Jumped a little with each pump of the oil. Does anyone have a part number for this? I've looked in the steiner catalog and they don't have it.

Regarding the rocker arm adjustment. Service manual says adjust when engine at operating temp..015, others do it cold. With tank off, I'd prefer to do cold, but am willing to go thru the hassle of doing it warm. Does it really matter? Also, Some talk about "staking" rocker arms. Soundguy ....do you recommend that?

Marlin

Fawken · Jun 25, 2015

I'd do it cold. If that .015 is a for sure, hot clearance, then go .017 cold. The push rods expand slightly when the engine is hot. 2 thousandths should cover it.

Soundguy · Jun 26, 2015

I do mine loose cold, then recheck warm. 15thou is the number, but its better a hair loose than tight. Tight gets ya burnt exhaust valves. I've never staked a set.

MarlinSlayer · Aug 9, 2015

Soundguy said:
I do mine loose cold, then recheck warm. 15thou is the number, but its better a hair loose than tight. Tight gets ya burnt exhaust valves. I've never staked a set.

So thread in a "Yesterdays Tractors" forums the same discussion. There was a guy there who said he was thinking about the thermal expansion and said he thought it should be tighter cold, so he took the trouble to do it again warm, and having set them at .015 cold, he warmed up the engine and checked it again and sure enough it was loose...like 017-018.....which from what I understand is not too bad as you won't burn out exhaust valves. Well, I got to thinking too and thought there's no way it should get looser as the rocker arms expand, and the valves expand, thereby narrowing the gap.....then it dawned on me that the head bosses the rocker arm assembly are much bigger than the arms and assembly themselves.....that head expands a bit with the heat and actually ought to lift the rocker arm assembly higher than the rocker arms/push rods expand and close the gap with a net "loosening" of the gap.

I had the gas tank off still after adjusting the valves cold the night before....Set it up on saw horses next to the tractor....ran the tractor and got the temperature up.....pulled cover and checked....lo and behold, same thing....clearance loosened way up. So I went back and adjusted everything to .015 warm, and it purrs like a kitten. Maybe I did it wrong the first time.

Soundguy · Aug 11, 2015

Do it however you want as long as they don't end tight. As I said, I get mine close cold, then check them again hot. Getting to the end of the maze is the goal, the path matters less.

One thing you have to remember is all the different metals in use have different thermal properties. Hollow push rods, hard valves, soft cast, oil cooled train, etc.. Then.. Are the seats new and the guides tight?

There is no one size fits all adjustment.. If there was, you wouldn't have to adjust them with a feeler gauge.