>>Real easy, take the oil filler cap on the valve cover off and hold you hand
>>over it to seal the opening, If it sucks its negative, if it blows its
>>positive-
>- which is good? bad? what? Please inform an uninformed soul.
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Michael,
It's not so much good or bad but what you car should have. Before "smog"
the crankcase fumes were simply vented out, usually through a tube from the
side of the block, extending just below the frame into the airstream. This
helped draw the fumes away from the driver (thoughfull?). With the advent
of smog controls this changed. Early cars (cars in general not LBC
specific) had the fumes directed to the carb. air intake. Not much later
the pcv (positive crankcase ventilation) valve was introduced. The fumes now
went directly to the intake (through this valve) another hose went from the
breather in the valve cover to the air intake (providing a clean fresh air
source) on early cars with no pcv valve you will have a slight positive
crankcase pressure. On later cars you will get a negative pressure (via.
the intake hose sucking the fumes into the manifold) some cars will even
stall (due to the surge of air) when you remove the oil filler cap while
running.
Barry Schwartz
Bschwartz@encad.com (work)
Bschwart@pacbell.net (home)
(San Diego)
70' Spitfire (under-going major surgery) , 72'-V6 Spitfire 70'GT6+
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