I dug out an older Motors Truck Manual to look at their oiling diagram to remind me how these engines oil..The oil is fed thru the oil filter directly to the cam bearings and then to the crankshaft..The oil galley is above the cam. Ok the lifter galley.Clear to the end of the block..I looked at a 153 CID inline (just a short inline six) I have apart.It appears to have a plug on the front of the block directly in line with this galley..The cam gear is still on it so its hard to see...I wonder about an obstruction in the galley..But if there was one you would think the crankshaft bearings would be starving for oil...BUT...how about the small passage way between the rear cam bearing and rear crank bearing..That must be where the gauge outlet is...Maybe there is an obstruction there..In other words every thing is being fed enough oil except for the gauge....Al...
