Where to buy Positive Valve stem seal for Farmall 100

Hi folks
Does anyone know if there is a source out there to buy a "Positive" valve stem seal rather than the more
easily available "Umbrella" seal for the valve guide? I need to finish the rebuild on my engine and the mechanic
I am working with simply refuses to use the Umbrella seals (he is convinced they aren't as good as the positive
ones) but after months of searching, I can't find any sources for them. I have a Farmall 100 with a C123 engine.

Thanks
Ramon

Any automotive machine shop that does head work should be able to find you some.

Engine parts suppliers such as Sealed Power have them listed in their catalog by dimension, and it's a matter of matching them to the valve stem diameter, and the OD of the valve guide.

If the guides have not previously been machined to accept such seals, that may need to be done.

Also, it will need to be determined that there's enough room for such a seal vs. valve lift.

I've linked a video showing the machining needed for the positive seals.
Video

Agree with Bob, machine shop can cut guide and provide seals.

tell your mechanic he is not working on a ferrari, and these engines had no valve seals from factory and the umbrella seal will do the job. having the guides replaced and clearance to specification is one of the most important factor's in any valve job. .0015-.003 is the spec range on guide clearance.the umbrella seal will allow a small bit of oil for stem and guide lubrication, while the positive seal will allow less oil for lube. to me this will allow for faster stem and guide wear. these seals are used more in the more modern engines.the umbrella seal or no seal will require a tighter clearance to control the oil going going into the guide. its whatever works for you though as installing positive seals requires a higher bill at the machine shop also. i dont use any seals on my old tractor engines.

Some thing a lot of guys never take into consideration when talking about valve seals or no valve seals. Will they run without them, of course. Will the guides and valves last good with a proper valve seal, also, of course. When an engine wears, all parts wear. The oil that is thrown around in the valve area is metered by the clearance of the rocker arm to the shaft. A small amount of wear in rocker arm area and shaft has very little effect on the engine operation but has a large effect on the amount of oil that is subject to being pulled down the guides. If you ever saw an engine where the rocker arm shaft was installed upside down and the oil feed holes were on top instead of the bottom, you can appreciate the amount of oil that can pass through a new, proper valve guide.

IH had one of their rocker arm suppliers miss the pinching of the lube trough on the top side of the rocker arm on some of the IH 460 and 560's. We sold one, a later model one and it burned a lot of oil. Service bulletin gave option of pinching the trough together to a specification or replacing the rockers. I don't remember which I did but it cured the oil burning. Pulled the head to clean all the carbon from valve head and combustion chamber.

Also, most oil is pulled through intake guides under light high manifold vacuum operation like putting around.

John Deere used positive valve-stem seals starting in 1960 on 1010s and 2010s. I have often wondered why since they did not use them on anything else for a long, long time. I have rebuilt many of those engines and I know the valve guides did not wear out any faster then the engines with no seals, umbrella seals, or valve-spring retainer o-rings.

Just buy by stem size and then might have to find a way to cut the guide-bosses for them to fit.

I think assuming valve guide wear due to no oil going down due to positive seals is an old wives tale.

I did have to research the guide and seals on my MH44 and buy a cutter that fit, I then loaned it to the machine shop.

Hey Everyone
Thanks again for all the advice. At the end (which is why it took some time for this update), my mechanic ended up fabricating the seals from scratch out here in Poland. I only hope they last a long time so I don't find myself in this situation again.
Ramon

Hey Everyone
Thanks again for all the advice. At the end (which is why it took some time for this update), my mechanic ended up fabricating the seals from scratch out here in Poland. I only hope they last a long time so I don't find myself in this situation again.
Ramon

You're in Poland? Now your forum name makes more sense.

If English isn't your first language, you sure had us fooled. From the responses I'm sure everyone assumed you were in North America where those items can be ordered from Amazon and will show up on your doorstep in a day or two.

I certainly hope he did not charge you for the shop time to go through all that trouble. He was the one that refused to use the umbrella seals.