Mystery pipe
 

I am nearly ready to swap out the Solex Cisac for the Weber DMTL, and I am reasonably content that I know what I need to except for one thing.

On the Solex there is a large bore rubber pipe leading from the underside of the plenum chamber, controlled by a solenoid, that runs off under the car beside the fuel flow and return from the tank. I have scoured a few books and the net and the best I can come up with is that it might be a float bowl vent. Not sure why a vent for fumes would go down rather than up unless it is positively drawn out by something.

Anyone know for sure what this pipe is and where it goes?

Also, a pic of the new setup, because shiny.

Resolution
 

For anyone who has this, it is the float bowl vent and terminates just outside the engine bay on the underside if the car. It must rely on low pressure from car movement to created partial vacuum in the pipe.

Petrol fumes are heavier than air. That's why unventilated inspection pits are so dangerous.

Petrol fumes are very bad.

Old discussion. Carbon monoxide is quickly lethal.

Unventilated pits with infernal combustion engine(s) running.... :(

.

That can be the 'one new thing' I learn today! Good to know.

Cheers.

Update, the Weber 32 34 DMTL conversion is complete.

Pretty straightforward except for connecting the PCV system as the K&N did not have a connection. This was solved using 1/2 inch BSP pipe fittings as shown.

One little fault. When I opened the throttle sharply (off load) the engine would bog and die. I suspected the accelerator pump, but it turned out to be the connection to the idle fuel cut-off solenoid. The voltage was all over the place due to corrosion in the connector.

Checked the oil separator and flame trap while in intake was off - clean and clear! Odd.

The car itself now runs a lot better, there is a large increase in power. The one caveat to this is that I replaced the spark leads, dizzy cap, dizzy arm and coil lead at the same time.

I carried out a compression test on all cylinders afterwards and got consistent but very high readings - 205-215 psi? I suspect my Sealey guage is at fault.

I would recommend this change if you're running and old Solex.

Systems binned so far - EGR, Pulsair, hotstart, airbox and intake piping.