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Datsun 521 breather?


Socalman

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Hello again knowledgeable people, would not allow me to upload photo, but there’s a steel hose under intake coming off the block into a rubber hose to intake manifold about 3/4” diameter. Is this just a crankcase breather? New manifold doesn’t have a provision for it, can I add a breather filter to it? Or can it be plug up all together? Thank you 

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What new manifold? All L series intakes have a threaded hole for a PCV valve. Yes that is the block vent and the hose connects it to the PCV valve. It's a very good idea to have a functioning PCV (positive crankcase ventilation)

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Well that's too bad. The PCV ventilates and draws away the combustion blow by, water vapor and gas fumes that will condense when the engine cools that will dilute the oil. You will need to change your oil more often. Do not plug the block vent or the hose on the top of the valve cover.

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Mike is right. I ran a large K&N breather filter on mine for a while, and I noticed that my oil started smelling like gasoline. I have since added back in a new PCV valve and rubber connector hose. The intake pulses pull all of that crap out of the crankcase. 

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Prior to about '62 the block vent tube just ran down the side of the block and vehicle speed would (sort of) suck the fumes out. In fact they were called 'draft tubes'. Paved highways were black with oil drippings in the center of lanes.

 

846-02795421em-1950s-automobile-highway-

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I have sidedraft Mikunis  and just open vent it but a breather catch Can will work also.  As motor speeds up it will actually suck air in. At idle blows out

 

Have had no proplems and don't change the oil a lot as I don't drive it alot

 

On my daily driver with downdraft I run the PCV valve as its there and hooked up.

Edited by banzai510(hainz)
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