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:
In the event that you might be facing oil pressure issues that do not respond to normal adjustment (35 to 40 psi fully warmed up at normal cruise, and 20 psi or so at idle), you might want to consider the regulating valve found in the overhaul section of our online catalog before taking on any heavier maintenance on your engine. Many overhauls have been headed off by the installation of this “early model” style of valve.
Another significant aspect to the problem of regulation relates to the fact that the orifice in the block is not always perfectly centered with the centerline of the threaded shaft.
The effect of this misalignment sometimes causes oil pressure to take a nose dive during an adjustment, as the threaded shaft nears the end of its travel and forces the ball (or even the pointed shaft of early model valves) off to the side of the orifice in the block. In these cases, it’s usually necessary to use the regulating valve seatdressing tool shown in the specialty tools section of our online catalog to bevel the orifice slightly, bringing it into alignment with the shaft or ball.
The following three photos show this tool in use:
To summarize the issue of oil pressure regulation, since we’ve been dressing all the orifices of the oil pressure regulating valve in the block and using early style regulating valves during our rebuilding operation, we have essentially eliminated the hassle we used to face in getting oil pressure to settle down during test runs.