Ford-Club Finland

CAM WEAR PROBLEMS

I alluded briefly to the CVH cam wear problem in the introduction. As this crops up so often on newsgroups and emails I'll expand on the matter. The CVH cam is lubricated by the oil that drips through little brass bushes next to the rockers. Even this limited supply can disappear if the bushes clog with carbon due to infrequent oil changes and cheap oil. Also the valve spring is extremely stiff compared to other engine designs. It generates a load at full lift of 220 lbs compared say to 125 lbs for a Pinto or Mini engine, 150 lbs for an MGB. This high spring load is necessary to control the heavy rocker and lifter and still only allows about 6,700 rpm before valve float starts. To compound the matter, Ford didn't use the best available material for the camshafts. "Chill cast" camshafts last several times longer than the induction hardened material used in the CVH.

Cam wear is therefore a fact of life with the CVH. Most other types of engine show little or no cam wear in normal use and if wear does start then it tends to accelerate exponentially leading to rapid failure. Standard CVH cams wear steadily from the moment they are fitted. I've never stripped a medium mileage road CVH engine that didn't have considerable wear on the lobes and lifters. The problem is worst on cylinder 4 next to the fuel pump lobe. This is nothing to do with the urban myth about cylinder 4 being furthest from the oil pump. Whoever started that one wasn't the world's deepest thinker. The oil supply runs up through the block between cylinders 2 & 3 so in fact cylinder 1 is as far from the pump as cylinder 4 despite being right above it. In fact there is a design fault in the engine which means that the cam lobes on number 4 are not properly positioned relative to the lifter bores.