When I put my finger on this hole to block it off the engine revs rise, is this normal?

I think that just allows the top of rubber diaphragm in the PCV to regulate to atmosphere pressure. There shouldn’t be any air coming in or out under normal operations, it could mean the rubber diaphragm is split or incorrectly installed

There’s a sectional drawing of the pcv on the site below, there shouldn’t be any air getting on top of the diaphragm

https://mgaguru.com/mgtech/engine/cv103.htm

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The rubber diaphragm is new and in good condition and PCV is put together correctly. I can feel air coming out of the hole indicated and when hole is blocked by my finger rev's increase.

Do you have a vacuum pump of some kind?

If you were to connect both fittings to a vacuum source they should not leak down. If they do then the diaphragm is leaking.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

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