Ace Bristol Electric Fuel Pump

[B.P.Bird]

Ian,
Yes the best way is as Keith describes and the second fuel line was the preferred works system for competition cars. Even a road car can exceed the capacity of the Bristol AC Delco mechanical pump if pulling hard uphill. The system installed by A.C. for competition often had one useful refinement: The mechanical pick up was above the floor of the tank by an inch or two and the electric pick up was right at the bottom of the tank. Thus the electric pump achieved three purposes, a booster for sustained full power fuel demand, a primer for start up especially after a period of disuse and a selectable fuel reserve.
Incidentally this practice was to be found on A.C. engined cars with two electric pumps for competition and also on Cobras prepared for competition with the Carter mechanical pump supplemented by a Bendix (Facet) electric pump, again the pick ups were arranged at different depths.
Barrie 

[James Eastwood]

Couple of further points:

1) - I run the boot mounted SU in series with the mechanical pump and only use the pump to prime, it works fine although it has not been given any extended uphill or high power tests.

2nd point) - I had deduced that the idea behind the two-lines/two-pumps approach was more to do with the design of the fuel tank being relatively flat, and using a fuel pump from each side of the tank guarantees one will always be covered when racing. I believe the clue to this is the fact that the lines only join at the fuel rail, and are not Y-pieced together further upstream.

(BTW - I have a box of old SUs if anyone needs a 'period' donor to rebuild, let me know  ).