The Ford Kent engine oil system by John McCoy
The Kent based engine goes back many years. Its early history began with the motor being fitted into the 1959 Ford Anglia. With a capacity of 996cc, the unit developed 39bhp (29 kW) at 5,000 rpm. From then it evolved though several incarnations, most notable being its many race applications. It was Lotus, Colin Chapman and Cosworth Engineering that brought the engine into the performance arena, and they had several reasons for doing so: it was compact, light, small and had a good bearing area, the bottom end was obviously quite stout, and it could support many cylinder head combinations. Continuous development resulted in many power units ranging from its 39hp base configuration, to those used in Formula Ford, Formula Junior, Formula Atlantic Cosworth BDD, and the top of the range, the 300hp Cosworth BDG. These innovations all essentially used the same bottom end or bearing area, changing out the cylinder head for more power and efficiency.
The engine’s long history of applications is stunning, and the service this engine has given is outstanding. In today’s applications, it is being pushed even harder, power outputs of today are optimized by modern refinements in cylinder head design and manufacture. Modern technology has, in fact, given this engine a new lease of life, boosting its performance far beyond original specification.
Standing back and looking at the engine’s design as a whole, there is one key component that has yet to be updated, Yes, you guessed it, the oil pump.
The pump used today is essentially the same as it always has been, and now pushing 50 years of service, is badly in need of technological improvements. It utilizes a gear and rotor (impeller), turning within a gear housing between faces in a housing bore (see above). This is a common design found in the automotive industry. The design has always worked fairly well if it is manufactured with tight tolerances and kept clean. However, if debris passes though the pump, the impeller tips are easily damaged, and further, if the debris gets caught in between the impeller/gear and the housing bore, the clearances will become enlarged. The result of an increase in these clearances is loss of efficiency, causing cavitation which aerates the oil.
The principal problem in mass production with this design is related to precision, or lack of it. Mass production manufacturers can’t afford to hand-fit and measure pump clearances. The housing is sand cast or die cast, then machined, at plus (clearance) tolerances. The gear impeller shafts are run in the housing, without bearing support, and as the pump warms up, a further increase in clearance occurs. This extra clearance decreases the pump’s efficiency. Add to this scenario the new thinner synthetic oils, and the pump will increase cavitation even more, thus supplying oil aerated, which results in higher engine heat, and eventual bearing failure.
Through the frustration of keeping his own race engines alive, and his pursuit to make more torque and power, John McCoy of Omnitech Engineering sought out a better pump. His solution was to take advice from one of the world’s best pump designers, Roy Johnson of Johnson’s HTP.
Roy took one look at the existing design and shook his head, observing, “same story – again.” It seems that Mr. Johnson is making a good business of upgrading old engines merely by upgrading the oil pump. He has done pumps for Harley Davidson, Mopar, Chevy, and Ford, working on old engines that just don’t seem to last, until now! His efforts have made big impacts in Nextel Cup, circle track, and drag racing.
According to Johnson, the heart of the problem is the typical pump design, and its inability to pass foreign material, compounded by lack of precision and/or excessive clearance. The stock pump has essentially no heat sinking capability, thus as it heats up, critical internal dimensions change. Present manufactures offer up high volume or high pressure pumps to attempt to fix the problem. Mr. Johnson points out, “you can’t fix an oil leak with more aerated oil. But rather, the pump needs to have minimal slip of the oil, designed more like a hydraulic system, and the supply of oil needs to be as pure as possible.”
John McCoy took his advice and installed Roy’s pumps on two of his most problematic cases, his own Twin-Cam Escort, and a Can Am race car fitted with a highly-built Buick-Rover engine.
