Farmall A valves

Doggonetractors · Feb 17, 2009

I just ordered new valves, springs and guides for my Farmall A with a C113 engine and I went by my serial # 152448 and it calls for 4.781" in lenght. I went to pull out the old valves and they measure 4.860" in lenght. Can I use the new shorter valves? Why are my old valves longer?

ScottyHOMeY · Feb 17, 2009

Not sure where you're looking for valve dimensions/specs. Only thing I've found so far is in the IH service manual, which calls for a length of 4-53/64, or 4.828, which is about in the middle of the range you're talking about. Maybe that changed over time, but I haven't found it yet.

Within the variance you give, as long as you have your tappet clearance set right, the only difference with a shorter valve (we're talking 8/100 between new and old and 4/100 from spec) and good faces on your rocker would be a little more spring compression.

Yes, there is a lot of compression on those springs, and somebody will call me on it if I'm wrong, but I think you'll be fine.

Janicholson · Feb 17, 2009

The serial # may not represent the head that is on it. The gasoline head uses the longer valves due to a smaller combustion chamber than a distillate head. hey cannot be interchanged. One option in your case would be to rebuild a gasoline head for a bit more power and efficiency than your current head. JimN

ScottyHOMeY · Feb 17, 2009

Okay, we were typing at the same time again. LOL!

Still, I guess I'm missing something. I'm guessing the gas head would have a smaller cavity/headspace requiring the longer valve stem to get down to it? Is that extra length (or lack of it) enough that the issue is mating/alignment/wear between the rocker surfaces and the ends of the valve stems when the clearance is set?

Janicholson · Feb 17, 2009

I didn't check the part numbers, I just have experience with the two heads, Dist/gasoline, they do not have interchangable valves. The difference between the two are obvious. If there is just a few thousandths difference it may be that the thickness of the new valve at its head/margin (rim between face and flat of head) is thicker, a good thing. The use of Dist valves will hyper extend the spring, and not work with the geometry of the rockers at all.
Soooo I think you were correct and I was on the wrong topic. A gasoline head would still be desirable if there is a choice. Thanks JimN

Anonymous-0 · Feb 17, 2009

Parts book for the A and B show only one head and one set of valves but they do list different pistons for hi-altitude and distillate. I have torn down a couple of them and the heads are the same but have found the different pistons. So the parts book backs up what i have found.

Farmall A valves

Doggonetractors

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