Although this isn't GM, we were wondering if any of you experts out there can help us. We have a '47 Diamond T model 509 with a Hercules JXC L-head (flat head) engine. When cold and under load, the oil pressure gauge drops to zero. This is not RPM dependent, as it is fine during idle. If pulling a grade when cold and you let off the gas, the pressure goes back to normal. At all other times, the pressure remains 30-40 lbs., which is optimal. Some have told us that this may be worn bearings. What do you think?
