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I have a 1964 mk2, 2.4 fitted with HD6 carburettors, (and the auxiliary carburettor). My problem is that I am getting really bad misfire when accelerating and petrol spirts out of the auxiliary carb, and all six spark plugs are very oily and blackened.
I have an electronic ignition and all new HT leads.
Any ideas and suggestions would be greatly appreciated.

Thanks in advance Martin

Hello Martin,

I don't know why petrol will come out of the starting carburettor, as there should not really be any fuel pressure there. Does it switch off?
What car did the carburettors come from? The 240 used HS6 carburettors and TL needles, as did the 3.4 Mk2 and 'S' type but with HD6 carburettors. Needles from a 3.8 engine will be richer.

I take it the misfiring is when the engine is hot, as a cold engine will tolerate an over fuel situation to a degree.

Make sure the air cleaner element is clean then set the carburettors to base settings:- Float hinge lever 7/16" test bar between the lever and the cover. Slow running screw (To the rear of the dashpot) screw closed then unscrew 3.5 turns. Mixture screw, (Below and forward of the carburettor main body acting on a small lever that goes to the base of the carburettor) ideally remove the dashpot and screw the mixture screw until the jet and jet tube are flush, then lower the jet by turning the screw 2.5 turns.

It should not require much deviation from this setting unless there are other mis set components, e.g. the jet in the piston setting, wrong needle or worn jet.

Let us know if that makes any difference and if you see any other signs, e.g. petrol dribbling from the drain tubes of the float chambers.?

Alec

Thank you very much I shall let you know in due course