A point of concern; If you vent the oily blow-by gasses from
the valve cover to the atmosphere, say via a long-ish hose under
the car, you will make more total emissions -- just not from the
exhaust. However, if you connect the hose to the carburetor/air
cleaner intake, you suck that oily stuff into the engine. The net
effect of the later is that the oil LOWERS the flash-point of the
charge (reduces the effective octane rating) and makes the car
more prone to pre-ignition and knocking.
Best regards,
Rick
> Later MGBs didn't use the PCV valve, just continual suction from ports
on
> each SU, through a Y-piece, to a vent on the front tappet cover. UK
models
> then had a breathing oil filler cap which completed the system. US
models
> had a restricted vent on the rocker cover which was piped to the
charcoal
> cylinder, and from there to the tank, anti-runon valve and carb float
> chambers. The valve in its normal running position allowed a flow of
fresh
> air through the system, and in its 'just switched off' position
blocked that
> port which meant the suction from the carbs was applied all the way
back to
> the float chambers to suck the fuel out of the jets and stop the
engine,
> preventing runon.
>
> With the UK system, at least, removing the oil filler cap causes the
revs
> (on a correctly tuned engine) to drop slightly, and you can feel the
partial
> vacuum by putting the palm of a hand over the open filler. If yours
doesn't
> do this then either the vacuum is not 'getting through' or is being
filled
> by a leak elsewhere.
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