Clipper.. long term running fault found.

Clipper 1.8 carb. EX. Webber 32/34 DMTL. Car running out of everything at 65/70 in top gear, juddering and really dangerous on a motorway, runs fine at lower speeds… Been like it for months and tried everything.  Thought it was fuel feed. Cleaned & rejetted carb, Checked for air leaks, Done all that business with the tank and fuel feed sytem, checked timing, new fuel pump, new inline filter, air filter, you name it.
Last attempt, bought and fitted a new Vapour separator just so I could open the old one and see what was going on inside (loads of fuel going back down the return pipe).. The new one didn't help.
There's nothing clever inside the separator, it's a pot with a dip tube with a fine filter so the fuel goes out from the bottom of the pot. The inlet and the return are at the top.  The return has a restricted outlet, the idea being that there is a bit of pressue in the vessel to push the vapours out, which gather there. The trouble is that the orifice is about 1mm, about the same as the float valve in the carb, this drops the delivery pressure and at high speed (on my car) starves the Weber. I clamped the return nearly closed but left enough opening to let a bit of vapour through and BINGO the car is transformed.

The Weber only needs 2-3 psi but there was just not enough flow.  Three other points, it may not be a good idea to ditch the separator as the pump may over-come the float valve (although unlikely) and if you have done away with the in-line fuel filter, the very fine filter in the separator will get all the muck and could easily block…that will send more fuel down the return pipe. Finally, this thing does act as a bit of a pressure regulator, connecting the pump to the carb might not be good for the pump.

This is a bit of a tale…might get it done in hard back..never know though it might help someone. JUST SO PLEASED TO HAVE THE OLD CAB BACK.