The brief given by this client was that this big old 7.5 litre V8 Lincoln was a little rough at idle and there was a slightly stronger than normal smell of petrol at idle also. 

(The below image is a generic image for the same car, model and year)

The challenge was to firstly find out if the smell of petrol and rough idle were connected to each other and then set about tuning this big v8 engine.  This was done using a combination of research into this car engine, carburation, fuelling and ignition.

The final result came down to 2 or 3 different factors which were all interconnected with each other.  Firstly the Motorcraft 4350 Carb was not indexed and rebalanced for its fuelling at idle.  Both carb barrels were wrongly set from their index zero start position and secondly out of synch with each other.  This was physically checked via the mixture adjustment screws, but also visually noted via a CO analyser and colortune visual burn colour.  In addition the ignition timing was out by a few degrees, checked via strobe and also verified by not giving an acceptable inlet manifold vacuum reading (Target 18.5 to 19Hg Inches).  By adjusting and fine tuning both ignition timing and idle mixture to both barrels a little at a time, the idle smoothed out considerably to what is normally expected for this vehicle type.  The final test with the client, as per the legendry smoothness of these engines, was to balance a £2 coin on the air filter case and dashboard when running.....and it passed with flying colours.

With today's fuel prices a gas lover like this big old V8 needs to be kept in tune because every mpg counts.....