James Sohl
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Ramp, There are internal differences regarding oil control. In early engines, the oil return passage from the exhaust-side cam box down to the sump tended to ‘air lock’, that is, windage and other sump conditions would slow oil draining back to the sump just enough to cause the cam boxes to slowly retain oil and fill up. It made the inherently difficult to seal cam covers that much more likely to leak. Also, oil flow to the camshafts themselves was a little excessive, making matters worse. There is no fix for the oil return. Later blocks are simply different in more ways than just to accommodate the lip seal. There are threads on the board describing how to put an orifice in to the oil passage that feeds the head, improving oil pressure generally, and lessening the tendency for oil accumulation in the cam boxes. The 907 engines are very much like any other Lotus product, continuous changes, poor documentation as to which change started with which (engine) serial number, and of course, LOTUS: Lots Of Trouble Usually Serious. Your mileage will vary. Actually, my ’73 ran quite reliably for almost three years, until I moved to AZ (and parked it.) It did leak oil from many places including those described above. I would not hesitate to buy the latest serial number I could find.
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