Rebuilt Engine Longevity

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I would be less concerned about breather filtration, it is primarily there to allow the dirty blowby from the rings to escape the crankcase, so it is generally blowing out not sucking outside air in.I would worry about a filter on the breather plugging up with carbon and sludge. Pierce’s system of dumping the breather blowby gasses between the air filter and carb inlet makes sense. The slight pressure drop of the air filter helps induce the breather flow (which actually shouldn’t need any help) and if for some reason the pressure goes negative it is drawing air through the main air filter.

A PCV system would be nice – it would ventilate the crankcase and reduce the sludge and deposit formation, but would be a non-trivial task to calibrate the flow and adjust the carb mixture to compensate for the ventilation flow bypassing the carb.

As a trivial aside, an engineer in the ’30’s determined that cooling the crankcase atmosphere by positive ventilation with outside air was significantly more effective at reducing con rod bearing temperatures than an oil cooler – most of the rod bearing cooling was via the rod thrashing around in the crankcase. He proposed drawing all of the carb intake air through the crankcase, which was pretty much the appropriate amount of air to cool the crankcase air. The first (unsolved) hurdle was how to separate all the oil flying around from reaching the carburetor and avoid rapid loss of oil – not to mention the smoke screen.

Jim

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