travlnman

Hey folks,

New to this forum. Not a new Z owner, but back in the game after many years off. Just picked up a '78 280Z. It's in good basic shape , with no major rust or other issues. One thing concerns me. Upon startup, the oil pressure is slow to build, no noise from engine, just slow. Once it builds, it will get up to between 40-50 PSI and stay there til hot. Once hot, while driving, 45-50 PSI is normal, but at idle, it will drop to between 10-15 PSI. There is a good oil supply up top, and no rattles or noises from the engine ever. The sending unit appears to be brand new. I have heard of the oil pump check valve sticking, or weak spring. Instead of throwing parts at it and replacing the whole pump, has anyone experienced something similar ? , I would like to wait, as a complete rebuild is on the agenda. The engine is strong, and has used no oil in the week I have had it (fresh oil as soon as I got home). No sign of burning oil ,i.e. no smoke , plugs are clean, and no leaks. I would think if the crank had that much wear as to drop the pressure that much, it would not be the smooth quiet engine it is. In the big scheme, oil pump is not that much, and I can do it myself. Just would like to get by for now, and max it all out later when I've got it apart. I'm thinking a 3.1L stroker kit and small cam for starters. Thanks in advance for your help.

rogoman

10 - 15 psi when hot is normal. The slow buildup of pressure with a cold motor may be due to the viscosity of the oil you're using. You should be be using a 10W-30 motor oil.

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travlnman

Cool. All of my previous Z's had factory gauges, which don't show as much detail as the larger aftermarket gauge that is in there now. The previous owner, was a bit of an unusual type,and apparently did not care for his vehicles as I do mine. He only had it a year or so, any longer, and he probably would have ruined it. Your right, I am using a higher viscosity oil, Shell Rotella T 15W40. The top end can use some cleaning out, and I'm sure the rest can too. I am considering using the Auto Rx product for cleaning if the Rotella proves insufficient. It seems to be doing well, the oil is a week old, and I'm considering changing it next week, as it has already turned much darker than new. I also understand that the newer turbo Z oil pumps have a better time of keeping the pressure up. That will be in my rebuild.