If you are refering to the umbrella seal that slips over the end of the valve guide, I don't see anything wrong with using both seals on your engine. Those seals were originally an after-market seal that was installed in addition to the O-ring at the tip of the valve. The umbrella seal became original equipment 2-3 years after its introduction as a service part to reduce oil consumption through valve guides. I think Perfect Circle Corp. developed those seals- just for historic interest. Originally you had to cut the outside diameter of the valve guide to accomidate the seals, but before long the guides were cut to fit the seals at manufacturing.
Also, for historic interest, Chevrolet stopped using the metal umbrella cap that covered spring and the valve tip when they began using valves with the O-ring seal, sometime in the mid/late 1940's, but I can't say with any certainty when that happened. Valves without the O-ring groove were still available for service parts until the mid-1950's, but were seldom used. The metal cap also contributed to valve noise.
Harvester
