SPICA Today – Part 2

by Jon Inge

In last month’s introduction, Wes mentioned that the SPICA fuel injection pumps “were far better than anyone ever realized when they were presented to America in 1969.”

   As a precision-built, positive displacement piston pump, its fuel delivery is strong and full at all engine speeds.  In contrast to one-dimensional race systems of the time such as Hilborn and Lucas, SPICA’s three-dimensional cam with temperature and altitude adjusters allowed for advanced and accurate fuel delivery management for everyday street driving.

   Wes has remarked that the quality of design and manufacture in these pumps are so high that, if properly maintained and used, they just don’t break.  “Proper use” means making sure that engine oil and filters are changed at the recommended intervals, and that the engine is regularly brought up to full operating temperature to drive off any accumulated moisture and condensation in the oil.  As with the main car engine, you don’t want sludge and potential rust forming in a SPICA pump.

   But there is one problem that virtually all SPICA units suffered from in the early 1970s, when lead additives began to be phased out of our fuel.  The plungers and barrels (P&Bs) in the SPICA pump are like miniature pistons and cylinders, but without sealing rings.  All that keeps the fuel in the top separate from the oil in the bottom is the incredibly fine clearance between the plungers and barrels; it has to be less than the size of a gasoline molecule.

   Made from very high quality materials, the P&Bs were designed to outlast the engine, and protected with high pressure engine oil and from additives in the fuel, they can.  But when lead and sulfide additives were banned from fuel from 1970 on, the P&Bs began to wear and allow fuel to seep through into the oil and back into the engine.  Today’s unleaded fuels contain additives that are equal to or better than lead and sulfides, but the damage has already been done.  You can smell it if you take an oil sample from the pump, or you can have the oil analyzed to make sure, but if you don’t take action your engine will wear prematurely.

   Wes’ partner Herb Sanborn meticulously laps worn P&Bs until they’re straight and true, then hand-selects them to get matching pairs with just the right clearance, something that can only be done by hand.  It’s incredibly painstaking and a real art, but once done, you should never have a problem again.  More next month.