To accurately measure the pressure you will need to connect a manual pressure gauge to the oil gallery somewhere. A favourite way to do this would be to temporarily remove the oil pressure light switch (front driver's side of the block, down low) and screw the gauge in using an adaptor as necessary. Most good garages should be able to do this.
Check it with a hot engine. Typical values (no experience of a V6) would be at least 3 BAR or so hot at 2500 RPM dropping at a hot idle to perhaps as low as 1.5 - 2 BAR. As I say, though, these are typical values and I've never checked it on a GM V6.
If the pressure is low, it'd be worth checking the pressure relief and safety valves, which should be accessible with the pump on the engine. Also, worth checking the pickup strainer within the sump is clear.
I believe there are more than one type of oil pump on the V6, and more than one style of lifter and T vent which must correspond with the oil pump. Worth checking that they are correct if the engine's ever had new heads.
If the oil pressure looks OK it might be worthwhile taking the lifters out and cleaning them.
Kevin
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Topic: Oil pressure? (Read 618 times)