As our technical service reaches more and more Atomic 4 owners, I suppose it’s logical that we would eventually run into a few of the “leftover” issues that bothered tech service folks at Universal in their later years. Erratic oil pressure in late model engines was one such festering issue in the late 1980’s, and it continues to show up on our plates today as well.
There are, of course, the few cases of loose electrical connections (or short circuits) between the sending units and gauges, but for the most part, indications on gauges have been real, and the late model spring and ball type of regulating valve has been the culprit.
Problems in late model regulating valves almost always relate to the fact that the spring-loaded ball doesn’t always seat squarely over the orifice in the block, through which oil is being supplied by the pump. It’s interesting to note that Universal tried several different sizes of balls during their later years, in an apparent attempt to steady out the regulating valves; however, it is not at all clear that either of the two sizes they tried made any significant improvement in the function of the valve.
In many cases, as the threaded part of the valve is turned in (clockwise) to increase oil pressure, the spring arches slightly so as to press against the side of the ball. This side load causes the ball to move more to one side of the orifice which allows more oil to pass through, instead of less. This is how you might get a slight decrease in pressure, while turning the adjustment in, in an attempt to increase oil pressure.
Other symptoms of regulating valve problems include oil pressure decreasing as RPM increases (another manifestation of the ball moving off center) and low oil pressure which doesn’t respond normally as the adjusting bolt is turned in. This problem is sometimes caused by a regulating spring that has worn thin by rubbing along the inside of the threaded hole into which the adjusting bolt is installed.
I’m not sure that we would ever have come to this conclusion on our own, but one of the good Universal technical service folks put a bug in our ear back in the mid 1980’s to the effect that early model regulating valves, which were built around a spring-loaded pointed shaft instead of a spring loaded ball, tended to provide much more consistent control. Below is a photo showing the inside of each type of valve:
