Mark,
If you have a Bentley manual you can check out the flow diagram for
better understanding of the flow pattern. If memory serves it will
show that the carbs are pulling the vapors from the the canister and
burning them when the engine is running. The canister "collects" the
vapors when the car isn't running so they are not vented to the
atmosphere....the whole idea was to reduce those types of fugitive
emissions from the gas tank. The bottom of the canister is open so
clean air can cleanse the charcoal of the vapors.
So yes you are pulling in what you might call "filtered air" while
running but it is laden with the vapors from the charcoal. I had
those type of carbs but replaced them with 1971 carbs from my rust
bucket TR6. I put the 72 carbs on the rust bucket but it wouldn't run
right without the hoses/canister hooked up so my experience is that
the carbs are engineered for that specific flow. Also I remember a
small brass insert with a small hole in one of the hoses?? that
limited the flow but I don't have the carbs anymore to look at them.
Bud Rolofson
71TR6 CC57365 (Good 6)
66TR4A CTC57806 (The Wreck-Almost parts)
66TR4A CTC57529 (The Project)
71F-250 Camper Special (Triumph Support Vehicle)
Z-50A Hardly Davidson 1977 Honda Mini-Trail Bike (Triumph Pit Bike)
levilevi@comcast.net
On Apr 26, 2010, at 1:15 PM, Mark Hooper wrote:
> 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
>
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