Flathead Distributor
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All the flatheads were pre-PVC systems and just had a road draft tube and a breather filter in the oil fill cap. Those two places are the paths of least resistance and any blow-by will be at those points. There was never any sort of a seal on the distributor on the later model top mount distributor engines. If you really feel like it needs one, the best thing to do would be to find an o-ring that is a snug fit in the timing cover and then have a machine shop cut a groove in the distributor housing for it similar to the later model V8's.
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