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Might help to have an illustration of the oil path to ponder. Pressure is caused by resistance to flow. Flow starts at the oil pump. You said that you installed a new oil pump, but who knows about its quality. The oil pump has a relief valve that could reduce pressure. The oil filter area has a relief valve but flow will still be resisted by the main bearings and the restrictor at the supply to the head. So that bypass doesn't really matter. Hard to know how much oil could pass through that restrictor to the spray bar. I think that I saw it in one of your pictures. And, apparently, some engines have another supply passage to the head at the front. It's not shown in the illustration but I have a vague memory of reading about it. A thought that just occured - the fact that pressure reduces at higher RPM might be caused by cavitation. Which could be caused by a restriction in the supply to the pump. So, it kind of circles back around to the pickup tube. Maybe you got a gasket on backward or something. The pump just moves volume. Pressure is caused by restriction.

There's a chance you have mismatched parts. The oil pickup could be wrong. The oil dipstick too which would show full when it could be low. 240, 280s and ZXs all are different. The high pressure bypass under the oil filter could have a weak spring. Teflon tape on the oil sender threads could be blocking the hole into the sender. That's a few things I've read on here over the years. If the top of the head is soaked with oil I wouldn't worry to much.

So Wally, this engine was running fine, and oil pressure was good, correct? If so, then there is really only a few things it could be. 1. The oil pressure relief spring may have broken, or lost its springiness. This would result in low, or inconsistent oil pressure. The spring can be removed without removing the pump. An easy check. 2. The builder didn’t use thread locker on the oil pickup where it attaches to the bottom of the cylinder block, and the bolts have come loose. This would result in air getting sucked in and the oil would get bubbles in it. You would see this on the dipstick and in the oil you splashed everywhere when running the engine with the cam cover removed. I doubt this is the problem. 3. the bearing clearances have somehow become too large. Excessive bearing clearances will definitely result in low oil pressure, but there will also be an accompanying knock as the rods and main bearings rattle about. Again, I don’t think this is the issue, as an engine doesn’t last long when this occurs. 4. If you reused the old oil pump, and it wasn’t disassembled, cleaned, and inspected to verify adequate clearances, it could be the cause of low oil pressure. 5. The correct amount of oil in the crankcase, and the correct dipstick. The oil sump capacity is 5 quarts if I remember correctly. Starting with an empty crankcase, and a new filter (should hold about one quart), refill the engine with the correct amount of oil, start it up, run for a minute, then shut it off. After waiting five or ten minutes, check the oil level. It should be within the high and low marks on the dipstick. (as for the question of the correct dipstick, have you replaced it with the one that was with the engine originally?)

Its called Jinglish.

Hey Chas, No, that was from American Autowire, but they don't maken one for Z's. But this brand is Painless, I think it's more of a universal wiring kit, but it will work fine, if you got the time to do it right. Could be that American Autowire also has universal kits, check their website. Gr Bart

I have achieved good result using JB Weld Plastic Bonder and reinforcing the back of the panels with sections of window screen to strengthen the area and provide a good base to fill any voids.