Oil pressure and Oil pump

[Richie]

Hey, so I was looking around and trying to find what the oil pressure should be at. looks like at 2000 rmps it should be around 20 psi. But when i start my engine it reads a little above 40 and when it warms up it reads a little less at 1000 rpm. I am running bigger flat head pistons on my L18 engine. Is this bad that my oil pressure is reading 40 psi? 

Also, I was looking at my oil pump while the engine was idling from underneath and noticed that around the bolt heads of the oil pump (the bolts that mount it) tiny little bubbles started forming. Best way i can describe it is like when you try to find an air leak on a tire so you use soap and water to find the leak. Is this a bad sign? 

Thanks

[datzenmike]

Cold oil pressure is higher than when fully warmed up. That's normal.

 

A engine with a lot of wear will have increased bearing clearances and oil will leak past these bearing faster and read lower at idle than a new engine. For example my old L20B, still a good running engine, was 17 PSI at idle. More than enough for idling on. When revved up about 56 PSI or what ever the relief spring was rated at. Most engines are 50-60 PSI when revved up.

 

40 seems a little low and it's probably your gauge. What are you using? is it known to be reliable? Some are pretty cheap.

 

There should not be air bubbles around the mounting bolts. Is there a paper gasket between the oil pump and the timing cover it's mounted on. No gasket the pump might be sucking air in with the oil. That would lower the PSI readings. Are the bolts tight??  Should be 8-11 foot pounds.

 

 

 

[Richie]

On 4/19/2022 at 9:17 PM, datzenmike said:

Cold oil pressure is higher than when fully warmed up. That's normal.

 

A engine with a lot of wear will have increased bearing clearances and oil will leak past these bearing faster and read lower at idle than a new engine. For example my old L20B, still a good running engine, was 17 PSI at idle. More than enough for idling on. When revved up about 56 PSI or what ever the relief spring was rated at. Most engines are 50-60 PSI when revved up.

 

40 seems a little low and it's probably your gauge. What are you using? is it known to be reliable? Some are pretty cheap.

 

There should not be air bubbles around the mounting bolts. Is there a paper gasket between the oil pump and the timing cover it's mounted on. No gasket the pump might be sucking air in with the oil. That would lower the PSI readings. Are the bolts tight??  Should be 8-11 foot pounds.

 

 

 

so I went back to datsun to check out the oil problem. I tighten the bolts on the pump and the bubbles were gone now...i know dumb move. So i watched my oil pressure when i start it up cold start i am 55, then after it reaches 140 degrees, it slowly drops down to a little above 20 psi at idle. I rev it up and it goes up to about 53 psi. The gauge i am using is speedhut quad gauge with their oil pressure sending unit. The sending unit is attached to an adapter 1/8npt - to whatever the BSPT is (i forgot). 

[datzenmike]

That sounds perfect. At hot idle, oil is bleeding out past the rod and main bearings, (specially worn ones) and all other uses faster than the pump can supply it so the pressure is low. My old L20B was 17 PSI at hot idle. That's fine. When revved up more oil is available and the pressure goes up. 50-60 PSI is normal.

 

I put a KA oil pump on and the hot idle pressure went up to 29 PSI with no other changes. The KA pump's internal rotors are 13% longer and move more oil. Top pressure is still about 55 PSI as this is the relief spring pressure.

[Richie]

On 4/22/2022 at 6:38 PM, datzenmike said:

That sounds perfect. At hot idle, oil is bleeding out past the rod and main bearings, (specially worn ones) and all other uses faster than the pump can supply it so the pressure is low. My old L20B was 17 PSI at hot idle. That's fine. When revved up more oil is available and the pressure goes up. 50-60 PSI is normal.

 

I put a KA oil pump on and the hot idle pressure went up to 29 PSI with no other changes. The KA pump's internal rotors are 13% longer and move more oil. Top pressure is still about 55 PSI as this is the relief spring pressure.

https://imgur.com/WOLXN2Q

 

Idk what that whining noise is but sounds like to me the oil pump is going bad......What do you thing?

[datzenmike]

The oil pump is the most lubricated part on an engine and likely the part with the least wear. L series have lots of moving parts and they all make weird sounds. I don't hear anything Abby Normal.

 

 

 

  Loosen the alternator belt and try it. This eliminates the alternator, the belt rubbing the pulley, the water pump and the clutch fan from moving. Sound still there?

 

[Richie]

2 hours ago, datzenmike said:

The oil pump is the most lubricated part on an engine and likely the part with the least wear. L series have lots of moving parts and they all make weird sounds. I don't hear anything Abby Normal.

 

 

 

  Loosen the alternator belt and try it. This eliminates the alternator, the belt rubbing the pulley, the water pump and the clutch fan from moving. Sound still there?

 

Nice video. 

 

https://imgur.com/wLNXI3c

 

The only thing i did not replace after i did the rebuild was the oil pump. When i rev the engine after the rpms settle it gets louder then quiets down. 

[datzenmike]

If replacing the pump I highly recommend one from a '90 and up D21 Hardbody KA24E or KA24DE engine. These have larger internal rotors and move more oil. Idle and low RPM pressure is raised. I think they are around $75 for an original Hitachi made one. Or grab one from a wrecking yard.

[Richie]

4 minutes ago, datzenmike said:

If replacing the pump I highly recommend one from a '90 and up D21 Hardbody KA24E or KA24DE engine. These have larger internal rotors and move more oil. Idle and low RPM pressure is raised. I think they are around $75 for an original Hitachi made one. Or grab one from a wrecking yard.

https://www.ebay.com/itm/154982603522?epid=1967578747&hash=item2415aedb02:g:0UAAAOSwmkFidXaD

 

Like this one?

 

 

I am gonna try your alternator method belt method first before buying parts. I am having a bad oil day today. I have oil leaking from many places but I think its from when i adjusted the valves and oil leaked around. 

[Richie]

Also, finding extra things around the truck lately lol 

 

https://imgur.com/31wdXgI

 

Is this part of the oil pan?? if so how the hell does it go on? 

[datzenmike]

That's the correct one by definition.

 

 

KA rotors are longer. Can't tell from the outside. Have to look in the hole when off.

 

Original pump. Top of rotor just barely visible...

 

KA pump. Top of rotor is very visible.

 

Know what to look for and check that it looks like the second picture. Get what you pay for.

[Richie]

2 hours ago, datzenmike said:

That's the correct one by definition.

 

 

KA rotors are longer. Can't tell from the outside. Have to look in the hole when off.

 

Original pump. Top of rotor just barely visible...

 

KA pump. Top of rotor is very visible.

 

Know what to look for and check that it looks like the second picture. Get what you pay for.

Would it still be ok if I went with a Hitachi original one? 

https://zcardepot.com/products/oil-pump-new-240z-260z-280z-280zx?_pos=6&_sid=a8e4ecd39&_ss=r

 

 

[datzenmike]

Sure, but I bet they cost about the same so get the larger output. The 280zx turbo also used a similar hi output pup. I put them on every Datsun I've had. Some of that noise you can hear may be the timing chain and the tensioner has an oil feed hole in the back. This adds a few pounds of pressure to the tensioner.

[Richie]

6 minutes ago, datzenmike said:

Sure, but I bet they cost about the same so get the larger output. The 280zx turbo also used a similar hi output pup. I put them on every Datsun I've had. Some of that noise you can hear may be the timing chain and the tensioner has an oil feed hole in the back. This adds a few pounds of pressure to the tensioner.

The oil feed hole that oils the chain might be making that noise? I am watching videos online and I can hear the same noise in some of the videos. Makes me think it might be the alternator like you mentioned, but i am not putting the oil pump passed me right now because like i said i have oil leaks pretty much everywhere right now. 

[datzenmike]

There us an oil hole on the front cam tower that sprays the chain and another at the bottom just above the crankshaft sprocket. The tensioner is a spring behind a tight fitting piston with a plastic (teflon?) covered shoe that bears against the timing chain to remove slack. The body behind the piston has pressurized oil so the shoe is pushed out by the spring and slightly by the oil pressure. It's not much about 5-7 pounds. Some oil is bound to squeeze past the piston and get on the chain, but not much.

 

[Stoffregen Motorsports]

Remove the belt and see if the noise goes away. If it does, it's not the timing chain.

 

That curved piece of steel is a bolt reinforcement plate for the oil pan bolts. It goes on after the pan to spread the bolt torque over wide area.

[banzai510(hainz)]

https://www.ebay.com/itm/333205764819?epid=202912852&hash=item4d949c7ad3:g:a2MAAOSwvrJhHj95

I got this one. Its a Hitachi unit. dont know if made in Japan it didnt say. Could be Mexico or South American

I got one and put on my L16 521. Intial stat its very good. At idle maybe 10pounds more if idle set correctly.

 

I say avoid the $25-45 pumps, could be Chinese. But they still work

[datzenmike]

Look at it this way oil pump is like your heart. You want the made in Japan heart for $110 or the one made in China for $25? If you do you probably like Chinese parachutes too.

[Stoffregen Motorsports]

I'll take the heart made in Pakistan and be somewhere in the middle.

[datzenmike]

Or the one stolen from a tourist in Mexico.....

[Stinky]

An old rule of thumb, for "Enough" HOT oil pressure is:

 

10# at idle

add 10# for every 1,000 RPM

 

So, 20# at 2,000 rpm used to be enough.  That said, I would like more than that.  And, that rule goes back to when a motor put out 1/2 a HP per cube (60 HP for a 2,000cc motor).  Your motor is stressed harder than that.

 

That said....you have plenty of pressure.