I believe that most adverse experiences with Lodge Golden Plugs are due to the following three factors, none of which is publicly recognised by the makers.
1. The plugs certainly resist carboning-up when slow running in traffic, i.e. they have a wide heat range; but they will not cope with an engine which is using half a pint to a pint of oil per 1,000 miles.
2. Due to the shorter time needed to initiate combustion, a surface discharge plug requires adjustment to the ignition setting which varies with engine speed, i.e. a different setting of the advance curve of the distributor. (A constant time difference becomes more degrees of engine crankshaft timing at higher speed.)
3. The surface discharge plug will ignite a weaker mixture at the same ignition setting, hence corresponding carburetter adjustments are also required, petrol consumption improves and the choke can be used for shorter time.
If the above considerations are neglected then the plugs will certainly not improve the performance in more than one respect and will probably impair it considerably in most others, e.g. the starting may be better, or the top end speed or the economy may be improved by a particular ignition and carburetter setting but not all three.
With my Minor 1000 I found that I had to “spread” the ignition advance by about 3° between 30 and 60 m.p.h. Having done this and retuned the carburetter I get quite lively performance with good economy; but if left standard then the spark is either over-advanced at low speed or over-retarded at high speed. The former probably accounts for some readers’ starting troubles, when they are not due to gross oiling up, and the latter for complaints of high fuel consumption or poor performance.
The adjustment to the ignition is hardly within the scope of most drivers, and a Tapley Meter is essential for this anyway, in determining the amount for a given engine type. Perhaps Messrs. Lodge and Lucas could co-operate—a simple replacement of certain components of the distributor would suffice. To add fact to opinion the following figures for my own car with Lodge Golden Plugs are given:—
Conditions of Test: Minor 1000—1959—with high comp. engine. 2-door saloon with driver and one passenger. Standard carb. needle. Esso Golden petrol. Speedo checked OK at 30 and 60 on Police mile. Engine re-ringed at 48,000 miles with Oilmasters. Golden plugs fitted 500 miles after rings and have now done 5,050 miles—untouched. Top gear.
Result of Test:
Road Speed m.p.h. 20/30/40/50/60/70/75/80
Tapley lb/ton 150/170/160/150/110/60/40/0