Okay I'm almost at my wits end with my Dart, and am just about ready to just run it and if it blows up, oh well. I have a 360 with W-2 econo heads and I keep having odd oil pressure issues. Last year I couldn't keep the pressure up when I was priming it, and finally traced it to a missing gasket behind the oil filter plate. Now I have oil pressure, but it fluctuates like crazy. When I start the car the pressure jumps up to about 80psi. It gradually drops to about 25-30psi as I let it idle. No problems there. When I start driving sometimes the pressure will drop to around 20 (even at around 3500rpm), but will shoot back up to around 60psi when I back off the throttle. Then after about 15 minutes of driving the pressure will drop to around 18 at idle and wont go above 35 when driving (and it still does the weird no throttle pressure jump). I'm running a high volume melling pump, but being the retard I can be sometimes, I reused the oil pump gasket when I quick pulled it to change pick-ups ( I was going to a new pan). This might be the obvious problem, but what else could be causing this? BTW, the Autometer gauge I have never goes below 10psi even when the car is off. This makes me nervous as hell that I might only have 8-10 pounds of pressure at times. Is this normal for a gauge like this?

The gasket you mention could be at fault but I am wondering about the accuracy of your gauge, especially if it is electric. If so it could be a faulty sender or gauge itself. I had one that acted that way. When your pressure is lower do you have any lifter noise? I would check out the gauge before I pulled off the oil pan and pump etc. Good luck to you.
John

You could have a broken pressure spring in the pump or the plunger is sticking every now & then. If your gauges check out OK I'd replace the oil pump.

The oil pressure gauge is mechanical. I'll try changing the gauge and if that doesnt do it I guess its time for a pump. Sucks because it only has about 2,000 miles on it. Anything else I should check?

The oil pressure jump when you let off the throttle indicates excessive clearance in the main bearings. Here is what's happening.

When under load or a steady cruise the crankshaft is pushed down against the lower main bearing shells allowing oil to escape around the grooved upper main bearing shells causing the oil pressure to drop. When you coast or let off the throttle manifold vacuum increases and the pistons pull the crankshaft upward into the upper main bearing shells reducing the area the oil has to escape and the oil pressure goes up. The hotter the oil gets the worse this becomes.

Try another gauge and another oil pump to be sure but if the problem still exists check you main bearings.

as mentioned #1 try another gauge #2 replace the pump(sticking regulator) & use NO gasket(I know they are included sometimes) & I am speaking of the small gasket where the pump sets into the main cap. I am sure hoping that with this gauge staying a 10 that IT is indeed bad. When you solve it give us the good news. EDIT & I am wondering if the pickup is too close to the pan.

Okay I tried a new gauge and all it confirmed was that I have even less oil pressure than I thought. Under normal acceleration the pressure would be around 25 and would steadily drop as low as 10psi. If I let off the gas it would sometimes jump all the way up to 70psi. Once the car was good and warm, idle pressure would somtimes be around 25-30psi but at other times it would around 15. I'm going to order a new pump asap and try that, but I just know that this thing will be getting a short block sometime soon.

keep us posted. I have alot in this one

The factory didn`t use a gasket on the oil pump mounting surface IIRC. I would try a new pump with no gasket. Mike