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L20B Oil Pump


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I've tried 10W, still get it and our summers are so hot that I end up with 10PSI oil pressure in traffic when it's 100 degrees out. Now I run VR1 to boost the pressure and it rattles less. I don't drive it in the cold - we salt our roads in the winter. I'm sure you're right, VR1 is like syrup. What would you recommend for an oil pump?

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Select oil grade by the warmest expected weather. If it's never going above freezing you can run 5W30, 10w is good from freezing down to -10F, 10W30 from freezing up to about 100F


Never run straight 10 w in the summer, but 10 w 30 would be fine from about freezing to 100F.


No oil pump made will suck up oil that is too thick from the cold. You are limited by the oil thickness and the atmospheric air pressure. Best thing is a block heater. Plug your engine in on cold nights.

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Wisconsin. Goes double digit -0 F in the winter. 15 w anything will barely pour out of the container. The oil pump can produce a vacuum on the inlet side but it only has about 14 PSI of atmospheric pressure to push the oil up through the pick up tube.  These are the limitations. 


So run thinner oil in the winter than the summer, or thin it out by warming it with a block heater.


I'm running 15W40 Rotella T a light diesel oil with high levels of ZDDP to protect my cam. It might dip to -7C or 20F where I am.

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Can anyone recomend a good oil pump for an L20B please? I get a little rattle on start up and sometimes on full throttle, think it's not getting enough oil, nothing in the pan though.



I've tried 10W, still get it and our summers are so hot that I end up with 10PSI oil pressure in traffic when it's 100 degrees out. Now I run VR1 to boost the pressure and it rattles less. I don't drive it in the cold - we salt our roads in the winter. I'm sure you're right, VR1 is like syrup. What would you recommend for an oil pump?


OK I re-read your posts. Cold oil is out if you don't drive it in the cold.


NEVER run 10W above freezing. If you drive above freezing only, then try 15W40 Rotella T like I do.


If you have a rattle on every cold start up even in the summer it could be rod knock and at full throttle could be pinging. In fact pinging isn't good for your rod bearings and it could be mistaken for a rattle.




1/ Try checking your ignition timing to eliminate pinging. Should be 12 degrees before top dead center.

2/ Thicker oil might improve the rod knock but won't fix it. Try 15W40


Oil pumps don't really wear out because... they are well lubricated. What happens is all the bearings 'bleed' oil which just returns to the oil pan. As wear increases on the bearings the pump can't replace it fast enough and the pressure drops. This is most evident at low RPM like idle. The oil falls out almost faster than the pump can push it in. When the engine is revved up it produces too much volume and a relief valve limits the pressure to about 55/60 PSI.


A high volume KA24E oil pump has larger internals and pushed more oil at the same RPM, so on the same engine it will produce slightly higher pressures at low RPMs. An example... my very tired L20B, had a hot oil idle pressure of 17 PSI. With no other changes but the addition of a well used KA oil pump, the hot idle pressure jumped to 29PSI. Top pressure is not changed and remained at 55 PSI. 




Try 1/ and 2/ above first.


If you want to improve idle oil pressure install a KA24E. It won't fix rod knoxk or worn bearings... it will raise idle and low speed pressure

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I just pulled apart a motor with the same issue, and slapped a small chamber head on it, put it into the race truck as a temporary motor.  I installed a new oil pump from Rockauto (standard pump - cast iron version) and the problem is resolved.  The oil pressure is significantly improved, no more cold start-up rattle, good oil pressure all around.  I'm not saying it'll work for you, but its a simple bolt-on part and worth a try.  


End clearances CAN AND DO wear out on an oil pump.  That gives oil a place to bleed off under zero pressure.  That will effect the overall volume and pressure.  

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Ka oil pump is higher volume and direct bolt in. But everything mike was saying still applies.

I'm about to buy a KA24e oil pump... It is bolt on right? I thought i read something about the shaft being longer than the Lseries or something.

I don't really know the oil pump well, but as far as I can tell they look identical for the most part.


100% direct bolt on? 

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You keep and use your oil / distributor drive spindle and only change the pump.What I did was lift the distributor out and have someone hold the top of the spindle with pliers so that when the pump is removed it doesn't fall down and out, messing up your ignition setting.


The old pump will drip oil so be ready for this with rags and fill the new pump with oil before installing.






The L pumps are very good pumps. They really don't go bad unless they have had a ton of metal through them. If it's in good shape just put some fresh gaskets on it and call it good. If you feel the need for some extra pressure, I think the KA and the 280ZX AUTOMATIC pumps were higher pressure and a direct bolt on.
I think this info is correct. I can't remember if the 280 pump was year specific or not. Can someone help me verify that?

Good stuff but they aren't really higher pressure, they are higher volume. They have the same pressure relief spring rate for about 50 PSI or so. The advantage is that more volume will give better pressure at low speeds. Sounds contradictory but it does. At all times the mains and rods, the cam and oil squirters for the chain have oil flowing into, through, and out of like a giant leak. At low RPMs such as idle, the motor can only supply a small amount of oil and the 'leak' is so much that the actual pressure can only build to about 35 PSI. If the pump were to be larger the excess volume would back up and increase the pressure.

So, on my tired old 300,000Km L20B the idle oil pressure with worn bearings when warmed up was 17 PSI. Normal running was still 45-50 but warm idle was 17. I installed a KA pump and the same warm idle jumped to 29 PSI. That's a lot of extra peace of mind when idling around in traffic or off road crawling.

If you look closely you can see that the internal rotors on the KA pump are longer, about 14% longer. You cannot tell from the outside if a pump is a high volume unit or not. It has to be removed. You don't have to take apart but you do have to look down into the inlet port of the pump. The taller rotor is much easier to see on a high volume pump than the other style. The inlet hole is the pear shaped one in the picture.


Regular volume oil pump. Rotors are down inside with the tops barely visible.

High volume oil pump. Rotor top edge is plainly visible to the eye.


D-21 Hardbody Z24i, KA24E, and KA24DE motors have them.
S13 240sx KA24Es (only) have them.
280zx turbo automatics w/ oil coolers had them.
Maxima diesels had them

720 Z24i motors did not.

The Hardbody motors are in the wrecking yards by the tens of thousands so get one. Even a used one will totally out flow a brand new L series pump, no problem. Offer the guy $10 for it and if he gets pissy about the price ask him if it seizes your motor is he going to replace it? That should get the price down.

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