[TR] TR6 evaporative filter - function or setup question

[Mark Hooper]

I have been doing a little engine bay cleanup on my 72 TR6. Now I am trying to
understand the evaporation setup.

I have a triple Stromberg setup with the nice piping kit to keep all the
suction on the crankcase working. I know how rottenly the car idles with
nothing blocking the pipe if the valve cover is off, so I have a nice little
plug I use to block the pipe when running the engine and valve adjusting.

So, I took off the canister to POR the brackets and clean up. I think I had
always assumed that the thing had a one-way valve at the bottom to stop the
vacuum from being reduced. Instead it seems that I can suck or blow on the
pipe quite freely. There only seems to be a white plastic insert in the top
port leading to the carb pipe that clearly restricts flow diameter down to
about 1/8" but is straight-through other than that. Seems strange. Is this
correct, or is there some piece missing that is supposed to make this a
one-way flow?

I had always assumed that the suction would pull on the crankcase and the gas
tank, except when stopped. Then I assumed that vapour pressure would push
gassy fumes out through the bottom of the canister via the charcoal pack. But
if there is no one-way valve, then it seems the engine is just sucking in
filtered air while running. What am I missing?

Mark Hooper
1972 TR6