Shortly after completing the Lanchester engine overhaul I caught a whiff of petrol fumes while running the engine and on checking found that there was a flood from the float chamber of the S.U. Carburettor - which had only recently been refurbished.

The normal response - cleaning out the float chamber (A), checking for dirt clogging the float needle or a leak in the float, and cleaning the piston in the main body of the carburettor (B) did not unfortunately cure the problem so I repeated the procedure again but to no avail.

I then turned my attention to the mechanically driven A.C. Petrol Pump (C) which I carefully dismantled, checked, cleaned and re-assembled, but without finding anything obviously wrong.

This was a puzzler until I scoured an old D.I.Y. Car Repair Book for clues.

After going through all the more usual possibilities,  it mentioned that the positioning of mechanical pumps could be critical since the rocker arm probably only made correct contact with the cam on the camshaft in the engine block which operated it, in one predetermined position. It was possible therefore that moving the pump away from the engine block could reduce the amount of movement generated by the cam on the rocker arm while conversely moving the pump nearer might result in bigger movements of the rocker arm/more vigorous pumping action.

At this point I remembered that the old gasket material between pump and engine block had been replaced as part of the recent engine overhaul but could not recall whether old and new gaskets were of equal thickness and by this time anything was worth a try.

As too much petrol was reaching the carburettor float chamber I made and inserted another gasket to lessen contact and - touch wood - there has been no flooding since.

(I know that the needle valve in the S.U. carburettor float chamber should prevent excess petrol entering, but presumably the longer rocker arm strokes were creating more pressure than the needle valve float or float chamber top seal could cope with?)