Hi everybody. I used to be on the british-cars list a couple of years
ago and have just recently signed up on it & this list. As usually is
the case when I write to a list, I need help.
I have a '72 MGB (part '69, part '74, part '75, and God knows whatelse).
Since moving from Ohio to Colorado a year and a hlaf ago, I really
haven't had the B on the road much, for two reasons; emmissions and
altitude. I haven't been able to get it to run well out here and since
my Ohio plates expired I have to get it past emissions to be legal.
It should be noted that this car has none of the required emissions
equipment on it currently. I have most of the pieces in a box
somewhere, but I think the way they do emissions out here for '81 and
older, if it passes the sniffer, they don't look under the hood.
Now, on to my question. How does all of the evaporative loss equipment
work on this car? Their is an outlet from each carb that looks like it
is supposed to go to the top of the charcoal canister. There is also an
outlet on the rocker cover that I believe goes to the canister and one
from the gas tank. Is this correct? Then there is a hose that I beleive
goes through the "anti-runon valve" to the intake manifold. The
anti-runon valve has another hose thatjust goes to fresh air.
I am not sure I understand how this is all supposed to work. I assume
the anti-runon valve opens up when you shut the car down to allow fresh
air in and lean out the carbs. Does this make sense? I don't understand
how the hose from the rocker cover does anything, because if the PVC
equipment is intact, there should be a vacuum on that line and it doesn't
make sense to me to pull air from the canister into the engine through
the rockers. And finally, what about the lines off of the float bowls?
Is air being sucked from the cannister to the bowls or from the bowls to
What am I missing? And since none of the equipment, i.e. PVC, air pump,
gulp valve, cannister, etc. is in place, what ports should be plugged and
which should be open? I had been running with the pipes from the
crankcase (both for PVC and rocker-to-cannister) open, the PVC ports on
the carbs blocked, the evaporative loss ports on the carbs open. Is this
how it should be, mechanically if not environmentally speaking?
What I would like to do is hook up the charcoal cannister and the PVC and
leave off the air pump and try to pass emissions. I don't have the
air-pump manifold or I would try to get that on as well, but I have heard
that it really doesn't do a whole lot as far as cleaning up the exhaust
Thanks for your assistance.
p.s. If anyone has some high altitude tips for getting this running well
enought o pass emissions, I'd love to hear them. Is there still a