Thread: Convert a chev 283 to 307 or bigger

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Yep, Dave nailed it. That little pencil point of contact between the cam lobe and the lifter crown on a flat tappet cam can, depending on valve spring pressure, generate loading in excess of 250,000 lbs per square inch. For over 80 years, this arrangement worked for the most part, due to the extreme-pressure lubricants that were added to off-the-shelf motor oils, including molybdenum disulfide, phosphorus and zinc.

Well, along came catalytic converters and the auto manufacturers began having to shell out for warranty problems with the converters due to their incompatibility with the oil additives. So, pressure from the car makers began to convince the oil companies to eliminate these extreme pressure lubricants from off-the-shelf motor oils. Well, you can see what happened then. Flat tappet cams began to fail by the truckload. This really didn't affect the auto makers, because by that time, they were all using roller tappet cams anyway, which do not need extreme pressure lubricants. Us hot rodders took it on the chin though, because most of our builds used flat tappet cams due to the higher cost of retro-fit hydraulic roller cams.

Hope this expains the problem. If not, ask more questions.


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