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This is the 7th in a series of articles. This time "How To" will address several problems that occur when asking for a "quart from a pint pot". Stanley, in his wildest dreams never envisaged the sort of horsepower that can be extracted today. However sound design and simplicity were his trademark, after all it was he who argued with Sir Herbert, and won, how the engine should be. Even to making allowance to enlarge the engine to 747cc, when Sir Herbert insisted on 646cc. This increase in size occurred early in manufacture and remained until the end. There are 100's of mods that can be done to improve life and power output, I will only deal with the more relevant. The standard oil pump runs at 1/4 engine speed and when reconditioned ie. Remachining the bore and fitting new or reground vanes plus new springs, is more than good enough for any situation, 100 Psi at 6000 RPM all day. I have written before about the size of the ball in the relief valve, too big is worse than too small, the correct size is .437" diam. It is usually possible to reseat the relief valve ball by putting the ball in by itself and with a short piece of round bar, giving it a medium to hard hit should do the job. When fitting the relief valve spring use a standard spring and pack it with 2 washers that will fit into the threaded nut which holds all in situ. Do not put the washers at the ball end. If you are working on a touring engine one more thing needs to be done,"radius" the hole where the oil enters the pump, without a 10 page instruction on fluid dynamics to explain the reason. Just do it. If on the other hand the engine is to be used for competition you have just started. First you must trap large quantities of oil in the lower sump area so that the oil pump pick up is always submerged. To do this you must dispense with the gauze oil tray "BA75" and replace it with an aluminium plate at least 3mm(l/8") thick. Using BA75 as a template cut, drill and shape the aluminium to be a replica in profile of BA75. In the centre of this plate drill or machine a 50 mm diameter (2") hole to allow oil from the upper crankcase to return to the sump, the, pump pick up must be changed so as to be in the middle of the sump and within 1 mm (1/8") of the sump bottom. To do this you need 1/2" dia copper pipe bent at 90 degrees, one end carefully silver soldered to the base of the oil pump over the pick up hole, the other cut at 45 degrees from the horizontal. Now with your new sump baffle fixed in place, you can imagine under neck snapping acceleration the oil is trapped in the lower half of the crank case, similarly when the brakes are applied the oil is again trapped, and hopefully the oil pick up is submerged at all times. Now the all important slippery stuff, "Oils ain't Oils" as the add once said. Your choice of oil today should be a modern multi viscosity type. Using oil with high numbers 50 60 are not recommended for racing engines, they are too thick, better to use 10 30 or similar, this is especially so if you are using slipper bearing shells on a modern 1-1/2 diameter crankshaft. Never overfill an engine with whatever oil, the crankshaft has to fight its way through it and in doing so you get less H.P. at the flywheel. John Bowring |