low oil pressure

[zclocks]

Also, change the oil filter when you change the oil. 

[Zed Head]

I looked in to cavitation a little farther and also came up with aeration.  This would be caused by a leak in the suction side of the pump.  The pump is above the level of the oil so you need a solid column of oil in the pickup tube to keep the pump full.  If there's a leak in the tube or at the pump's suction side it will pull air in along with the oil.  So, you could have an obstruction or you might have an air leak.  Not sure but you might be able to rig something up at the oil pump inlet to see if the tube is pulling air along with the oil.  I don't have a mental image of what would be involved there.

Pretty interesting stuff.

https://www.machinerylubrication.com/Read/30768/cavitation-or-aeration

https://www.machinerylubrication.com/Read/28767/gear-pump-cavitation

[Patcon]

The 3 psi loss when revving is really odd to me. I think Zed is thinking in the right direction.

[Racer X]

12 hours ago, Wally said:

just saw this page. it explains location of 2 different type springs.

https://www.thezstore.com/product/2838/factory-pressure-relief-valve-oil-pump-70-83-zzx

That is the relief I mentioned. I have worked through many different combinations of spring setups to tune the oil pump for the race engines I build. I’ve used two springs, one inside the other, single springs of varying rates, and made shims to fine tune the pressure in the system.

The rule of thumb for oil pressure, in any engine, is 10 pounds for every 1,000 rpm. So at 5,000 rpm you want to see at least 50 psi, 8,000 rpm (yes, I turn these engines that fast) you need 80 psi.

A couple pounds more is OK, a couple pounds less, not so much.

 

The spring and valve are under the fitting circled in red.

Edited January 26, 2023 by Racer X

[w3wilkes]

As far as oil type used I've been using

Driven HR1 15W-50 Conventional Hot Rod Oil (drivenracingoil.com)

and have been very happy with it. Has all the additives for our older engines.

[conedodger]

It should be about 10psi per 1000rpm. So idle might look very low. The needle should move with revs but more of a rise and hold. If it is doing this, quit looking at the gauge. It sounds like you don’t have a problem. 

[Wally]

i've got oil drained, filter off. Here is image behind filter. I see the Oil Filter Relief Valve. I have a new one. I am nervous about trying to get it out though. Any advice on that. 

 

btw, the ball was froze. i was able to get it to moving freely though. i imagine still best to replace it.

Edited January 30, 2023 by Wally

[Wally]

had to loose sway bar but got oil pump in nice and tight. I am not wondering if i really need to remove oil pan. I am not sure what the point is anymore. I looked through drained oil and didnt see anything out of ordinary. was all nice and clean with no shavings or anything

Edited January 30, 2023 by Wally

[jonbill]

the relief valve is only active if the oil filter is clogged. I'd leave it. 

don't you need to take the oil pan off to confirm there's not an air leak in the oil pickup to block? 

[Zed Head]

On 1/16/2023 at 1:05 PM, Wally said:

oil pump is new

I think that you're headed in the wrong direction Wally.  I only mentioned the oil filter relief valve as an example of a relief valve.  The pressure is still caused by the resistance to flow of the main bearings and head oil supply orifice.

The pump produces pressure which forces the oil through the passage that the gauge port is on.  If there's nothing holding the flow back then pressure will be low.

I'd put the old oil pump back on before doing anything else.  If pressure is still low then the problem is farther down the line.  Or on the supply side, with air leaks or obstructions at the oil pickup.

[Racer X]

8 minutes ago, jonbill said:

 

don't you need to take the oil pan off to confirm there's not an air leak in the oil pickup to block? 

If the oil pickup was loose enough to allow air into the oil passages, then the oil would get foamy. The oil in the videos doesn’t look like it has air in it (although the video quality is poor)

[Racer X]

2 hours ago, Wally said:

i've got oil drained, filter off. Here is image behind filter. I see the Oil Filter Relief Valve. I have a new one. I am nervous about trying to get it out though. Any advice on that. 

 

btw, the ball was froze. i was able to get it to moving freely though. i imagine still best to replace it.

Someone is selling these?

Who?

12 minutes ago, jonbill said:

the relief valve is only active if the oil filter is clogged. I'd leave it. 

I agree.

If the ball can be depressed with a finger, and is clearly free to open when needed, there isn’t any reason to mess with it.