DeltaCoupe

Hello and a good day.

I have a problem. After we rebuild the Olds 403 and we did start it according to the rules ( with the paste on the crankshaft ). But now we are almost as far as we can hit the road again, we have the next problem and we hope that someone around here can help us.
When we made a test ride, after 2 miles the oilpressure light went on ! So we stopped immediatly. But we found out the next strange thing : When we have the car in "N " we have a pressure of 2 bar ( 29 psi ) , but when i change to " D " then we fall down to +/- 1 bar ( 15 psi ) ( or less )
Does anyone now what the problem is? Inside the engine everything is new.
I'm looking forward for your answers. For so far : thanks a lot.

Greetings Alex

67 Cutlass Freak

Hello, My name is Dave. I think we will need some more information from you about your build. There's a lot of things that can affect your oil pressure. There's a possibility one of the galley plugs was not installed correctly. The primary things that will contribute to low oil pressure are a weak oil pump or impropper clearances on the crank bearings. There's a possibility that the oil pressure sending unit has gone bad. I would recomend hooking up an oil pressure gauge tool to get an accurate reading at idle & @ 2500 RPM hot and cold. What viscocity oil are you running? What oil did you use to break in the cam? Please give us all the details on your build specifically bearing clearances so we can hlp you better.

Octania

Disconnect the OP sender wire!

But, seriously... replace the pressure sender switch?

0.5 bar is not bad for IDLE pressure, not much is needed at idle anyhow

Sorry, "0,5" bar!

I believe the stock LIGHT sensor is supposed to close the contacts below ~7psi or what about 0,3 bar?

Yeah, put a Bourdon tube ["real"] oil pressure gage on it to verify pressure. As long as you have ~10psi at idle,and ~40 psi above that, you should be fine.

Oil viscosity [thickness] is crucial to getting the right pressure, and easily changed.

If all that doesn't fix your problem, then we can discuss things like missing oil passage plugs, pump specifics & alterations, and bearing clearances...

pogo69

Since you mentioned the engine was just rebuilt, you might want to rule out the easiest things first...connector ,sender ,gauge ,proper oil.

Mikes65

How is the Temperature? As the engine temp goes up pressure can drop as things expand.

Rickman48

When you change the oil and filter, you may want to cut open the filter for inspection.
If clear of bearing material, you should be O.K.

DeltaCoupe

Thanks guys for all the reactions! At this moment i have no further info with me, cause i'm at work. Later on when i'm home i'll try to give you all more info. For myself i thought it was also not enough information for you , to give me a good explanation.
But i was a little to late to change everything.
Greetings Alex

DeltaPace77

You did right by not driving the car, cause low oil pressure can't be good. Strange things can happen, as have a good one about a buddy's new Chevy 400 build. Kinda close to this one, as the guy kept borrowing my engine picker, ext. Was getting strange looking stuff in his oil, that turned out to be bearing grindings. Everyone was scratching their heads on this one, even the builder. Turns out the oil pump mounting bolt on his engine was to long pushing on the bearing. No one would admit to this, so ended up costing him. Two different enginges here, but goes to show, weird stuff happens. I'd start by installing a pressure gauge myself.

Oldsmaniac

The pressures you give are normal for a stock Olds V8. The dash light should not come on till about 3psi...crazy right? So your light should not have come on with 15psi.

DeltaCoupe

So , we disconnected the OP sender and problem solved.
This time we took with us all the right tools. 'Cause we were sick and tired of the problem. With all the answers and solutions you gave here on the forum, we went tonight to my " problem child ", and guess what : We put a nanometer directly on the engine and we had with a cold engine 3.5 till 4.0 bar ( 50 till 58 psi ) and after 20 minutes running by a temp of 90 degrees ( 194 Fahrenhei ) we had a 3 bar pressure ( 43 psi ) Later we put the car on 700rpm and we had 2.8 bar ( 40 psi ) So for about 99% the sensor had played with us. Probably went death on the road.
So let's hope this is last problem before we can go to the "MOT testing" and when that is good, we can let the American horses run over the Dutch highways. Cannot wait!
By the way : Many thanks for your answers , solutions etc.

L69

glad it was was something silly

z11375ss

Man did you get off lucky. Good for you.

Octania

"So , we disconnected the OP sender and problem solved. "



When the banging starts, turn up the radio!

DeltaCoupe

Jep. We did get off very lucky. Now it's only changing the voltage regulator. That one died years a go i think. And then we can drive again. After 2 years it's about time to have some fun!!!!!!!