> Aaaah, this is where it gets more interesting. I have the tubes connected
> from the carbs to the cannister, and there a a tube from the cannister
> to the valve cover, and then theres the breather tube from the timing
> cover to the carbs. GREAT...a complete circuit I here you all say...
> well, not quite...because on my canister theres another tube which is
> just cut off at the cannister (not blocked off though).
Okay, look at your canister. It's got three tubes in the top and one
tube in the bottom, sticking out the side. On top it's got one 1/2"
hose in the middle that goes to the valve cover, right? That's the
OUTPUT hose, something that had escaped me for years. That drives the
whole engine-as-PCV-system, per the manual. The other two itty bitty
hoses (both, um, 1/ 4" I think) are vapor hoses for the fuel system.
One of them runs from the carbs to the canister; the other should
disappear back into the depths of the chassis.
The bottom hose is the INPUT to the canister. It draws air through
a hose that's supposed to go down to the bottom of the engine compartment
so that fresh air goes past it. Pressure from the float vents seems to
drive this whole thing, but I can't determine that for certain.
What is certain:
Air comes in the bottom of the canister. It collects vapors from the
carbs and from the gas tank in an expansion cylinder inside the canister
(there's also a charcoal filter pad at the bottom that needs to be
replaced from time to time). This vapor-air mixture then goes out the
top of the canister, through that 1/2" hose, and into the valve cover.
Once in the valve cover, it winds its way down past the cam, over the
casting webs, and down into the crankcase, where it then goes through
a metal flame trap and out the breather tube (on Marcus' car, on the
timing cover and on my car, on the front tappet cover). The breather
tube connects to the carburetors, where the passage of air over the
ports causes a depression in the ports which draws the vapors out of
the crankcase and keeps up a constant low-pressure suction on the whole
system.
> I am assuming that this is where the tube from the air pump went too.
No, that went into the gulp valve.
Ah! Do you *have* a gulp valve? That's a potential big vacuum leak,
one that could be causing all sorts of rough-driving problems.
The air pump has two outputs, one of which goes to the air injection
rail into the head, the other of which goes to the gulp valve. The
gulp valve has two 1/2" hoses -- one in from the air pump, one to the
manifold -- and one teeny (I think it's 1/8") hose that acts as a signal.
When you lift off the throttle, the gulp valve opens and lets air come
into the intake manifold (after being pumped and filtered by the air
pump).
The usual way to hack the air pump removal is to put a piece of duct
tape over the input to the gulp valve, tie-wrap it down, and leave it
at that. This works until the duct tape stiffens up or works loose,
at which point your car will want to die unless you rev it to 3000 RPM
or so. The right way is to remove the elbow from the intake manifold,
tap the socket, and plug it. A decent interim solution is to get a
good rubber plug for the gulp valve outlet, use some sealing compound,
and hose-clamp it. That lasted quite some time on the old B motor.
> All my emmissions stuff is gone, so does this giant PCV system not
> work too well now and will it effect the way my motor runs??
The PCV system is pretty much independent of the air pump. The only
connection they have in common is the intake manifold, and that's
downstream of both of them.
--Scott
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