[Mgs] MGB valve cover/crankcase venting

[Paul Hunt]

No not the pre-PCV system but post PCV system where ports on the carbs 
between the butterfly and the piston provided a relatively constant 
low-level of vacuum.  I doubt you will detect operation of the valve at the 
inlet manifold - unless it is faulty and stuck wide open!  With the engine 
running it will be constantly open but only slightly, the only variation 
being it will be open a bit more at wider throttle openings to achieve much 
the same relatively constant but low level vacuum in the crankcase of the 
later system.  The best way to check the operation of the valve is to look 
for suction or vacuum on the crankcase side of the valve, but it is only 
going to be a couple of in. Hg. so may not register on a gauge.  The easiest 
way is to put the palm of your hand or a sheet of paper across the open oil 
filler orifice and it should be sucked gently down.  It should also cause a 
slight change in engine idle as you remove and replace the oil filler cap, 
even a ventilated one.

PaulH.

----- Original Message ----- 
> Paul, if you mean that the crankcase vent is
> connected to the atmosphere side of the air cleaner, I
> agree.  Yea, it can goober up the carb with oil but
> the vacuum applied is acceptable AND always on the
> atmosphere side of the venturi.
>
> For my car, I'll just replumb it back to the way it
> was designed and see if the engine behaves.  I have
> installed a vacuum port on the inlet manifold so I can
> connect my meter.  I may be able to detect the valve's
> operation there.