John---It does indeed look like someone used whatever parts were
available at one time on this '71. Rex pretty well has most of the
questions covered in his reply earlier. I will add some things that may
also help you unravel this. Much you may already know, so skip past
those parts.
It's important that some "breathing" take place to ventilate the
crankcase. The valve cover tube and the hose from it is sufficient, IF
the hose can vent. The carbon canister is only a good choice if it too
can vent, as engineered by Triumph. This may not be happening, as once a
hose is connected to the carbon canister, I'm kind of sure it takes a
vacuum source to relieve it. A hose to the air filter doesn't do this.
One could do the next best thing here and either vent the valve cover
hose to atmosphere, or find/fabricate a place on the air filter canister
for this hose, (and the gas tank vent tube.) It's not really necessary
to connect vacuum to this hose to draw out crankcase fumes, or blow-by,
as it's sometimes called. If there is pressure here, it will come out if
allowed. If it can't vent "normally" it will try to push out past the
valve cover gasket, it's studs, dip stick, oil seals, or the easiest
path, making a mess as it goes.
I do not think this is creating the head gasket blowing, either. These
gaskets were designed to take the tremendous pressure of combustion.
Next time the head is off, 8~) see if the cylnder bores and head is
supposed to take the later head gasket that fits into the counterbores,
or not! When you wrote head gasket, could you have meant valve cover
gasket?
Dick T.
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