[Mgs] MGB valve cover/crankcase venting

[Paul Hunt]

Hi Rick - I did wonder after posting if you meant PCV rather than gulp 
valve.  The problem with the PCV valve is that they *do* fail, but usually 
the problem is noticed more as high oil consumption being sucked through the 
valve due to the much higher vacuum in the crankcase.  The restriction on 
the air inlet (filtered and restricted oil filler cap on non-emissions cars, 
restricted port on the rear of the rocker cover on emissions cars) will 
limit how much the faulty valve can weaken the mixture.

Without a form of suction on the crankcase it won't be *through* ventilated, 
and that is what can result in internal condensation and corrosion, as well 
as fumes getting into the cabin.  But sealing off just the suction port 
won't result in crankcase pressurisation to the point of blowing seals as is 
occasionally mentioned because the crankcase has originally *two* paths to 
the outside world - the filtered and restricted inlet as well as the suction 
port.  Sealing just the suction port will allow normal crankcase pressure 
changes to be vented to the outside world perfectly safely, via the inlet as 
long as that is left open.  Seal both at your peril, though.

IMHO it is far better to have a PCV, and check it from time to time by 
monitoring the vacuum at the oil filler orifice, than do away with the PCV 
on the basis that it may, at some point in the future, fail.

Cheers,
Paul.

----- Original Message ----- 
>   Paul, my worry is that the crankcase emission valve
> may not function as designed, allowing a vacuum leak
> to the crankcase, thereby leaning out the mixture.
> Yes, I have carefully rebuilt the valve and it looks
> good but 'looking good' and 'working correctly' are
> not the same thing.
>
>   So the question becomes, if I effective plug the
> line from the cover to the valve, will the crankcase
> 'breathe' adequately at the stock filler cap?