Original application is "air injection check valve". Very common on American cars of 70's and 80's. Have them try mid 80's Mustang 2.3 liter.
If no luck locally, Summit carries the Moroso version -->> http://www.summitracing.com/parts/MOR-97800
That looks like a check valve that is used in a smog system. They were used in a lot of american cars between the smog pump and the air injection lines. The very same valves are used on the Moroso pan-a-vac system. If that is what you are looking for they can be had by the bucket full at pick and pull.
thanks guys,is this thing really nessary to have on my boat?its hooked up to my valve covers and dumped into my headers. can i just eliminate them with no problems or do i need to have the one way diafram there ?
The one way valve stops exhaust gases from blowing water and debris back into the valve covers. If they are not working properly, they will not pull vacumn on your crankcase as they were intended to do. They also help blow-by oil from running out of your breathers and making a mess.
The common name or mechanics term would be a gulp valve. it is in simple terms a one way valve used on the exhaust side of a combustion engine. They have become very popular as a pan-e-vac valve for most "performance" engines. M