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Crankcase Ventilation

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doates

doates

Senior Member
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Hello,

I have a 70 Spit with SU's and a Smith's PCV valve mounted on the manifold. At idle should the valve allow full manifold vacuum at the rocker cover? I pulled the hose yesterday and covered with my thumb and I thought it was going to give me a hickey on my thumb. If my oil dip stick is not seated all the way I can hear the vacuum whistling by and the engine runs poorly. I am beginning to wonder if this is part of my surging at idle problem.

Thanks in Advance
 
You should get minimum flow at idle and low speed. Max flow should be at high speed or under load. Sounds like you have a problem there with the PCV valve. More info here.
 
There were different types of Smith's PCV valves; sounds like someone installed the wrong kind when they modified your car.

Might be worth looking for the kind that does limit vacuum applied to the crankcase; either the Smith's type or the more common type shown in Art's link.
 
I wouldn't exactly call it "pressed" into the manifold but it does mount there. I can easily remove it by hand but it is kind of a taper fit and when squirted with carb cleaner it doesn't appear to leak.

When I remove it and suck on the manifold side there is little if any restriction. If I blow from the valve cover side it prevents flow.

Thanks...Dennis
 
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