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low oil pressure at start


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#1 pwrcat4000

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Posted 27 October 2017 - 09:59 AM

I am having low oil pressure at start up I can hear the valve train taping for about 3 seconds then the pressure comes up I am thinking about replacing the oil pump I believe it is on the right side of my 1077 L20b?

What do you all recommend?

Other problems
Still getting hot when I turn it off (have not had time to check the thermostat for the bypass hole)
It still runs over the mark when I am driving and if I am in a hurry it will build heat.
I have played with the timing and it is better but still over the line on temp.
These two problems are at least going to reduce the life of the engine at worst break it.


1971 521 "Rat Suey" L20B/ 5 er I mean 4 on the floor.


#2 Crashtd420

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Posted 27 October 2017 - 10:04 AM

The only thing I've been told is get a ka oil pump, More volume and they are suppose to fit the L block....
Hopefully someone will verify that statement

#3 racerx

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Posted 27 October 2017 - 10:22 AM

What's the oil pressure reading? Numbers?

#4 datzenmike

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Posted 27 October 2017 - 10:33 AM

Unless you have a mechanical gauge the readings are useless. Electric gauges are just like your gas gauge, they take 20 seconds to read half full. Engine oil pressure is almost instantly there. If you have rod /lifter noise on cold start up, you probably have bearing wear. Valves won't tap from lack of oil pressure. They are either too loose and tap all the time or they don't. If anything they tend to tap more when they warm up and the clearance increases. 

 

Get a $6 filter with an anti drain back valve. Look for it. I doubt this will help but cheap enough fix if it does. If you haven't kept up your oil change interval of 3-5K then change it. Don't use synthetic oils. You can run 15K but it will have 3-5 times as much dirt and crap in it.

 

Use 15w40 Shell RotellaT(4) or Chevron Delo 400 diesel oils or equivalent in your favorite brand. The diesel oils are high in anti scuff ZDDP and what you should be running today. Oil makers have been steadily reducing the zinc levels yearly as all gas engines made today and for over a decade, use roller cams. Datsuns use lifters or direct contact rocker arms and need this protection. Thicker oils cushion better anyway. NEVER run anything 5W in it.


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#5 Royal Sierra

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Posted 27 October 2017 - 12:12 PM

I always run castrol gtx 10-40. Not synthetic. I guess I will switch to the delo 400. Makes sense

#6 datzenmike

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Posted 27 October 2017 - 04:28 PM

The GTX might be ok if it's marked 'racing oil' Maybe someone else can speak for this. Racing oils tend to have the original high levels.


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#7 mainer311

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Posted 27 October 2017 - 06:00 PM

Valvoline makes a conventional VR-1 with high zinc. Spendy though.

#8 Doctor510

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Posted 27 October 2017 - 06:23 PM

The only thing I've been told is get a ka oil pump, More volume and they are suppose to fit the L block....
Hopefully someone will verify that statement

Verified, same as the 280ZXT, high volume pump. Tray changing the oil & filter first, pretty normal situation.  I have both the idiot light and a mechanical gauge. 



#9 datzenmike

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Posted 27 October 2017 - 06:56 PM

The KA24E from the 240sx but not the later KA24DE as they were the internal style pump.

The KA24E or KA24DE from the D21 Hardbody all had the external oil pump.

 

Yes the L28 turbo automatics had something similar but they are hard to find. Pull one for free from an old Hardbody KA, bang done.

 

My high mileage L20B had a hot idle oil pressure of 17 PSI. With no other change than a KA pump the hot idle oil pressure jumped to 29. That's a 70% increase at idle and the pressure is faster rising as it revs up.

 

It's high volume, so same number of turns gives more volume, so pressure goes up faster than the oil can bleed past all the bearings. It does not have higher pressure overall. They are still set for about 55 PSI. It just gets there quicker.

 

7jkQ4Im.jpg

 

There is no way to tell from the outside. You have to remove and look into the inlet port. In the above picture of a KA high volume pump you can easily see the top edge of the rotor.

 

 

V2fckkS.jpg

 

You can easily see that this rotor in a regular everyday garden variety L or Z series oil pump is shorter and sits well down in the pump case.

 

 

Below is the comparison between the regular and the KA oil pump rotors. The KA trochoid rotors are 13% longer

 

sBzw2v1.jpg

 

 

If you order one make damn sure you check and know what to look for. I bet there are more than a few out there that think they have a high volume pump but do not.

 

Hands down one of the cheapest easiest things for peace of mind.

.


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#10 Royal Sierra

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Posted 27 October 2017 - 07:27 PM

Good lookin out..will go look for one as well. My L16 knocks slightly until it gets oil pressure for those first miliseconds during cold start.

#11 wayno

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Posted 27 October 2017 - 07:36 PM

I bought a oil pump from Melling engine parts(part# M111) and it appears to be a high volume type. 


 

 


#12 datzenmike

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Posted 27 October 2017 - 07:37 PM

Then the bearings are worn and over clearance. During shut off, the oil drips out of the bearing and isn't there when it starts. You could try a thicker oil but a larger pump won't help much for the start up. Or replace the rod bearings.


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#13 racerx

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Posted 27 October 2017 - 08:01 PM

Castrol gtx has zinc

#14 banzai510(hainz)

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Posted 28 October 2017 - 01:42 PM

try a better oil filter first.   had a bad one in my jeep Cherokee once . oil pressure would wonder around. swap filter now good.

thinner oil


Throw on some Weber sidedrafts, Rising Sun hood.... call it good

#15 pwrcat4000

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Posted 28 October 2017 - 06:49 PM

Well this has been very informative as always you all are the best and I really like to hear your responses.
 

I have noise for maybe 1 sec definitely valve train sounds like the front of the engine at start regardless of cold/hot
The noise stops when the idiot light goes off I don't have a mechanical gauge
I don't rev the engine or try to drive or anything just let it idle
 

i change the oil about every 3-4k or when i install a different motor whichever comes first

I have been using Oriley SAE30 (sounds like this is not advised)
I just use the O'Riley MicroGard - Oil Filter Anti-Drainback Valve Included (maybe i should be using a wix or a mobile one)

So will a new oil pump help with start up pressure
if yes I am looking at these

ENGINETECH EP094
https://www.rockauto...1208977&jsn=679

HITACHI OUP0023 {#1501040F00A}
https://www.rockauto...jsn=679&jsn=679
 

DNJ (cheapest)
https://www.ebay.com...8E/302000794790


1971 521 "Rat Suey" L20B/ 5 er I mean 4 on the floor.


#16 datzenmike

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Posted 28 October 2017 - 07:11 PM

Ultimately worn parts may make a little noise on start up but keep in mind that there will be oil on the parts and it's only for a second or so at low engine revs with no load.


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#17 banzai510(hainz)

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Posted 30 October 2017 - 05:27 AM

Hitachi would be best . But I had a Hitcahi said made in Taiwan on box also????????????WTF

 

adjust the valves and try oil filter. 8 min job to swap this out.

 

Nothing wrong with 30 wt if in a hot climate or summer. I would have no proplems running it.  Just harder to find it.


Throw on some Weber sidedrafts, Rising Sun hood.... call it good

#18 pwrcat4000

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Posted 14 November 2017 - 11:24 AM

Sorry I took so long to get back to you all the diesel oil and a new filter fixed it no rattle at all and no light Fixed it all for under $30 thanks to all for futer referance to anyone on this thread I used the standard O'Riley filter MGL51515 and Valvoline Diesel Blue 15W40.


1971 521 "Rat Suey" L20B/ 5 er I mean 4 on the floor.