Engine oil pressure

by rogal_tx Fri Sep 04, 2015 8:26 am

Hi, I've got 73 el Camino with 350 motor out of 86 corvette.
I installed aftermarket gauges for oil, temp amp. They all work.
What I can't figure out is why my oil pressure sometimes showes between 12-14 psi and 40-50psi while driving. I replaced the oil pressure gauge last night thinking it's bad but new gauge showes same think. Any help is appreciated.

by thatfnthing Fri Sep 04, 2015 8:46 am

Pressure should fluctuate between idle (i.e. standing at a light) and actual driving. Or are you saying it will go up and down while you are maintaining a steady RPM on the highway?

If the latter, I would suspect the oil pump itself.

by rogal_tx Fri Sep 04, 2015 8:53 am

When I replaced the gauge last night and I fired it up it was reading 40 psi at idle. And sometimes reads 12 psi at idle. When I'm driving it fluctuates between 40-50 psi or 12-14 psi depends on what pressure the gauges will read at the time of start up. I hope this makes sense?

by rogal_tx Fri Sep 04, 2015 8:57 am

Pressure gauges needle stays still at idle.

by Tom77 Fri Sep 04, 2015 9:18 am

Oil is much thicker at start up. Even at 100 degrees here yesterday my gauge showed almost 60psi at start up and down to around 30 once up to running temp. I use Rottella so it is a little thicker than most but that's what the engine builder suggested. Hope that helps.

by rogal_tx Fri Sep 04, 2015 9:49 am

So as long oil pressure is registering on the gauge I should not worry wheathe it reads 12 psi or 40 psi. Would that be a true statement?

by Tom77 Fri Sep 04, 2015 10:11 am

Yep as long as you dont hear the lifters. If you ever hear those all of a sudden no matter what the gauge says shut it down.

by rogal_tx Fri Sep 04, 2015 11:48 am

Thx for info

by chevellelaguna Fri Sep 04, 2015 5:13 pm

As long as you have 10 psi per 1,000 rpm you're good. 20@2,000 etc

by Oldschool454 Sat Sep 05, 2015 9:20 am

All of the above, yes. and just my two cents, but depending on if you use an electrical gauge, or a mechanical one with oil running through the tube, and the the diameter of the line you have the oil running through. All of those might read a bit different.

by rogal_tx Sat Sep 05, 2015 5:36 pm

I use mechanical gauge with I think 1/8in tube.

by chevellelaguna Sat Sep 05, 2015 6:24 pm

I would think that there would have to be a fault within the gauge. Are you replacing with an identical brand gauge? Is it a cheapie auto parts gauge. Your oil pump wouldn't generate one pressure... Then another the next time you start it up.
I could see 12-14psi at idle... But then it should increase as the rpms increase... So at WOT you should have 40-50 psi. What viscosity oil are you running? How old is the pump? Sounds like it's a regular pump based on the max pressure.

by rogal_tx Sun Sep 06, 2015 9:04 am

Yes I'm replaced it with same gauge. They come in sets of three: oil, temp and amp. Bought it at AutoZone about $40.
I'm using synthetic 10-30 high mileage oil. I'm assuming pump is original from 86.

When I'm driving oil pressure fluctuates by maybe 5 to 10 psi from idle pressure.

by 77mali Sun Sep 06, 2015 9:55 am

Have you moved the location of where it connects to the block?

by rogal_tx Sun Sep 06, 2015 10:36 am

It connects in the back, right behind the distributor.

by 77mali Mon Sep 07, 2015 8:43 am

With my truck I'm at about 50 psi on a cold start (5 qt pan). After warm up it runs at 40 psi max with acceleration on the hwy and 20 psi @ idle or in traffic. Check your oil level just to make sure it's not a little low. If you want try moving it to the port by the oil filter & plug the one by the Dizzy. If it reads better on in the new location, at least you know its not a faulty gauge.

by rogal_tx Mon Sep 07, 2015 10:30 am

I will try moving it by the filter. Honestly had no idea that there is a port there.

by 77mali Mon Sep 07, 2015 7:04 pm

Here it is on my late 80's block. Good luck.
Engine oil pressure <a href=

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by thatfnthing Tue Sep 08, 2015 9:30 am

Earlier blocks (like my 69) do not have that port, so don't be surprised it it isn't there.

Something else occurred to me -- could there be crud in the pan? If something is floating around in the pan and blocks/unblocks the oil pump pickup randomly, that could cause a weird fluctuation in pressure...

by chevellelaguna Tue Sep 08, 2015 12:13 pm

Good point about the pickup getting blocked. I've seen gasket material and crap wedged in the screen.

by rogal_tx Tue Sep 08, 2015 1:19 pm

I might have to pull the oil pan and clean it to be on the safe side. Thanks for info.

by Joe73 Tue Sep 08, 2015 1:29 pm

I dropped my pan back in the 80s and found a bunch of my plastic cam geat teeth all stuck in the pickup. So I had to change my timing gears and chain as well.

by chevellelaguna Tue Sep 08, 2015 8:46 pm

If you drop the pan you may as well put a new pump and pickup in it.

by Joe73 Tue Sep 08, 2015 9:02 pm

chevellelaguna wrote:If you drop the pan you may as well put a new pump and pickup in it.

And oil pump driveshaft with METAL collar.

by jerry46765 Tue Sep 08, 2015 9:53 pm

You are going to remove the oil pan? Really?

I have to ask, do you ever hear lifters clattering? If you don't randomly hear lifters making noise then there is likely no problem.

The pump varies pressure based on engine speed (rpm) so pressure will vary. 10psi is no problem at idle and 40-50psi is fine while driving.

Did you just install gauges and then see this problem?

Save yourself alot of work, double check obvious stuff like oil level.

Thanks -

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