Oil Pressure Qs - & believe it or not I searched

[heavy85]

Two questions (ref L28):

 

1) Stock oil pressure guage reads just under 1/2 at idle (and about 3/4 at elevated RPS's) which I think it should. Now I just installed a 20 PSI oil pressure switch and idiot light and below about 1000-1200 RPM the light comes on. So does that make sense that the stock guage reads almost 1/2 way up yet it's below 20 PSI and more importantly is < 20 PSI at idle too low?

 

2) When I first start the engine it takes a couple seconds to build oil pressure - that doesn't seem right to me but is this normal for an L series? Related to this is I noticed that the oil filter didn't have much oil in it when I changed it at 100 miles (rebuilt engine). I'm used to oil dribbling all down the engine on other cars when you take the filter off of but I only got a couple of drops of oil which is obviously related to why it takes a couple seconds to build pressure. One other piece is it's a turbo block running N/A without the oil cooler - I just left the sandwhich assembly off from between the filter and the block which I know deleted the by-pass valve but that shouldn't have any affect?

 

Thanks

Cameron

[akeizm]

Well low oil pressure at idle you shouldn't worry about. Because the motor is only rotating at 900rpm the oil pump will only be rotating slowly (and because the motor is just idling and not underload you don't need as much oil as you would at lets say 3000rpm). And it seems pretty normal to build up oil pressure in the motor as it would have drained down and the oil will need to make it way back up to those sections.

[slownrusty]

My ZXT records 10psi of oil pressure at idle and 45psi at WOT, based on my Autometer Mechanical gauge.

 

Hope that helps

[Tony D]

General rule of thumb used to be 10psi per 1000 rpms. Now with coated bearings and synthetic oils, they have revised that even lower.

 

10psi at idle would be a normal figure, and you should get to "regulated pressure" before 3000 rpms. If you don't reach the higher pressure by 3000, there are clearance or supply problems.

[Here comes trouble]

z oil presure...when cold at idle..>high pressure..........when hot at idle..>low pressure.............when low oil level or old oil...>low pressure .................high rpm..>high pressure........an "aged" stock and aftermarket electric sending units can cause some false or inaccurate readings... unless you have a heavy duty oil pump the stock units will have variances in oil pressure that at times can cause you more than casual concern. I once hooked up a mechanical guage to check possibilty of a faulty Datsun oil pressre gauge by the use of a T fitting. The two guages acted the same to the pecularites of a Z's oil pressure.. I had a 300 nailhead Buick with high compression that ran a steady 15 pound oil pressure at any RPM or under any condition and that was consdiered normal by Buick

[Guest bastaad525]

My ZXT records 10psi of oil pressure at idle and 45psi at WOT' date=' based on my Autometer Mechanical gauge.

 

Hope that helps[/quote']

 

 

That's just about exactly what my stock '72 240z gauge gives me as well, and I was under the impression that this was normal.

 

Also, when the motor is cold, pressures are a bit higher, 60-70psi.