A friend told me that Atomic Four engines sometimes have erratic oil pressure, and there are several ways to fix the problem. What is he talking about?
Erratic Atomic Four oil pressure is a problem caused by Universal’s change of the adjustable oil pressure regulating valve internal parts to a spring and 3/8″ ball from a spring and pencil-shaped plunger around 1965 – 67. [Check yours and if you have a ball measure it to determine if it is .375″ (3/8″) or 7/16″ (.438″)]. The spring and ball was not as good at controlling the oil pressure as the old spring and pencil-shaped plunger so they started using a larger 7/16″ ball around 1972. This still didn’t always work, and so they released a retrofit kit which was actually the old spring and pencil-shaped plunger. The kit was accompanied by a service bulletin titled “Atomic Four – Installing Oil Pressure Plunger Kit #256575” which is in the Atomic Four Parts Manual on page 98A/B and details a procedure called “seating plunger or ball” which can be used to improve the performance of the existing ball or when a pencil-shaped plunger is installed. Dangerously high oil pressure (ie over 60 psi
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