Oil pressure drop??

[GladwinJay]

I have just rebuilt my 3.1 with pretty all new/reworked components.

Now when I start it up I have about 75psi at the oil gauge, but then after 10 min of driving it slowly drops to about 15-20psi. And at idle at a stop sign or something it hoovers above 0. I have no leaks and no visible blue smoke. I am tempted to add aftermarket gauge but I have no reason to suspect a faulty gauge in the cluster.

Anyone have ideas??

Thanks

[robby1870]

Which year oil pump spring did you use?

[GladwinJay]

I just bought the melling replacement pump.

[robby1870]

Okay, then, what year is your motor/car/truck?

[gpse3400]

If you have the silver oil pressure sensor toss it in the trash and go to the parts store. the New design is black plastic and is made better. Those silver sensors are known for showing high pressure then eventually showing lower than normal readings. its either that or....your clearances might be too much....I'm leaning towards the sensor. The oil pump is another thing but they are for the most part made well.....

I'd also get a cheap mechanical gauge, remove the oil pressure sensor, attach the gauge and read the oil pressure that way. Just to be on the safe side. Oilf fitler removal is pretty much required to get to the sensor.

[GladwinJay]

Well thanks for the ideas but now I can hear the dredded "death tick" so I parked it for now until I can get new rods.

This is the first motor I have rebuilt myself and I skipped the plasti-gage procedure thinking that if everything was new I would be all set, well I guess the $50 rods I got off e-bay tought me a lesson......

[geoffinbc]

The tick is probabally the valvetrain and not the bearings.

[robby1870]

The tick is probabally the valvetrain and not the bearings.

Yeah, a bearing or something, is going to make much more noise than a tick

[88jbody]

Always plastigage!

[GladwinJay]

Well I tore into the bottom end and re-torqued everything and jsut gave it a look for obvious wear. Nothing but the side-to-side play on the rods.

Here is what is puzzling me...I get good oil pressure when cold, while driving at constant speed it gradually drops, but if I were to let off it recovers a little bit. And for the tick/knock I only hear it at 3k and above. So the valvetrain issues kinda make sense.... Let me know what you guys think. Should I look into new rods??