Help! No oil pressure! 4.6 V8

[ChrisJC]

The pressure relief valves are a bit prone to sticking. I had one do it at one time, so I fitted a 'tadpole' valve instead.

I am not totally convinced about those either though, and since then I have gone to the later distributorless timing covers, so hopefully the problem has gone away anyway.

Chris.

[stevieturbo]

Oil pressure switch plugs a hole. Stops leaks lol.

maybe the engine just came with it, more than likely it did as a 4.6 or whatever.

And there is no before or after the relief valve in the sense you are talking.

Before....is essentially anywhere in the high pressure circuit.

After, ie if the valve open, ie excess pressure, just becomes low pressure returned to be fed back into the pump. Just like you opening a tap before the tap was the high pressure side, the water discharged is low pressure.

Ideally you'd measure engine oil pressure from the main engine oil galleries though for a final true picture of what the engine gets, as opposed to at the pump.

Not 100% sure if the original sender port is before or after the oil filter even.

[rich112]

Seems to be running ok. Once warm, I am still getting good pressure at idle, about 20 psi.

Will post a video of it running for comments!

[SuperV8]

I think the issue was the relief valve. It was tight in the bore. Not rock solid, but it didn't slide out on its own.

It's a nice sliding fit now.

So I have just fired up the motor and it's running, without any horrible knocking or rattles, but it needs proper ignition timing setting.

Riddle me this: I thought the oil pressure should limit at 28 or 30 PSI and at idle I should see 10 or maybe a bit less.

When I first got the car, I am sure this is what I was seeing.

Now I am getting 34 PSI at about 1500 RPM and even at idle it's 25 PSI. (EDIT: Maybe this is just because it hasn't reached normal operating temp yet...)

Looking at my oil pump there is a warning pressure switch and a gauge BUT they come off different places. The warning light goes nowhere as there isn't a light on the dash that I can see.

Is it possible that the gauge is reading pressure before the relief valve?

My pump is an uprated one I believe. Not with the add on sandwich block, but I think its a later pump as the gears are quite deep.

Maybe this is how this sort of pump should run and before the relief valve was dropping the pressure all the time? It just got more stuck in the wrong place and completely dumped all the pressure...

I'm running some Morris Golden Film SAE 30 mineral oil through it at the moment to flush the old stuff out and I'll replace that with 10W40.

(Edit: Will set timing and run longer so oil gets warm and monitor pressure tomorrow!)

There's where the oil pump gauge and warning switch are plumbed in:

20210715_190422 (Medium).jpg20210715_190435 (Medium).jpg

The oil viscosity will directly effect gauge oil pressure all else being equal. Have you changed from a 10w40 to a single grade SAE30 oil? - This will be thicker than a 10w40 multi grade oil when cold - so that would result in a higher gauge pressure until warmer. When hot it would be thinner - so you would expect the reverse so lower pressure compared to the 10w40.