Triumph Repair: Valve stem seals, valve stem seals, triumph engines

Question
I had bronze valve guides (O.D. .50" w/no lip on top) installed in a 1500 MG Midget cylinder head as well as hardened ex. seats. I purchased a dual spring set to replace singl springs and machine shop could not find valve stem seals that  could fit inside inner spring. Recently I saw an ad on e-bay for viton seals guaranteed to fit dual springs- they don't. Seals I.D. is .50" same as guide O.D. Do you know of a seal set that will work or will I have to have top of guides machined to accept a seasl? Thanks!

Answer
Hi Mike,
This is a subject I am divided on. Since the Spitfire/Midget 1500 don't use seals as many British cars don't. I often thought about adding seals. However, I do believe it would be difficult to be sure that the stem to guide were lubed with a seal. I believe it would depend a lot on crank case pressure, exhaust scavenging or back pressure (depending on exhaust system design and even cam profile) Even a small carburetor and restrictive air filter would change the design of an intake stem seal compared to a dual carb system with a free flow air filter. It is a complex problem and I am not sure even the manufacture has done much research other than trial and error.
This is a decission that should have been made before the guides were installed so you could have turned the guide down to fit a small OD seal. Thus not foul on a two row spring set.
On an engine that never had seals (like most of these Triumph engines)I would have just turned a knife edge on the top of the guide to prevent "puddling" of oil or just put an "O" ring on the stem like the MG has used on their engines for many years. Much of the oil that gets on the stem comes down from between the keeper halves. All of these factors enter into any design of seal or no-seal design.
I played with a design (on paper) of what I thought would be a great design. I would cut an internal groove on the bottom (port end) of each guide for a Teflon "O" ring and have a drilled drain hole to the crank case and a oil pressure feed to the stem close to the top (spring end)with a good lip seal. This would be a lube and cooler for the stem. Especially for an exhaust stem. If you look at the present design on the intake side it is a full "Loss" oil system where intake manifold vacuum plus crank case pressure runs oil down the stem into the intake and is burned in the combustion chamber. The exhaust is "hap/hazard" lube system as long as back pressure in the exhaust system don't exceed the crank case pressure you get some lubing of the exhaust stem. When back pressure exceeds crank case pressure you can see what you get.
There are many small OD stem seals but the guide would have to have been turned down to accept them before the guides were installed. If they have been installed you can't knock them out now and turn them down.

It it were mine an the guides were already in, I would just look at the MG "O" ring and adapt it to this engine.

That is the best I can think of. Let me know how it turns out.
Howard