620 L20B CAUSES OF ENGINE SEIZURE?

[slepe67]

I purchased a '77 620 KC with a seized up L20B.  I have a replacement junkyard engine to put back in temporarily.

 

Previous owner claims to have had low oil pressure & replaced:

Oil Sump

Oil Pump

Oil Pan Gasket

Oil Pressure Sensor

 

After replacing all of this, he claimed (from the CL ad): "this was my daily driver till the engine seized.  Didn't know the truck still had low oil pressure after all the parts were replaced."

 

It's locked up.

 

I'm out of town at work, so without being able to tear the engine down, what could cause this?

 

Spit-balling here: 

Blocked main bearing oil passages (in the block)?

Pump 1 was shot, and Pump 2 was faulty?

Pump  incorrectly installed?

Oil Pump pickup blocked?

Do these oil pumps have screens?  Perhaps that was clogged?

 

I guess I'm just curious as to see what caused the seizure.   

 

Since my 'new' engine is from a junkyard, could I re-use some of the new parts above (after a damn good cleaning)?

 

 

[DanielC]

Datsun L engines are pretty much bullet proof.

I am running a junkyard L-20-B in my 521.  I did a compression test before I installed the engine, and also cranked it with an oil pressure gauge.  It had sufficient compression, and oil pressure.  I install it, and have been running it over a year now.

[Stoffregen Motorsports]

Low oil pressure on a Datsun L motor is usually caused by main bearing wear, both on the journals and the thrust.

 

A blown head gasket is more likely a cause of it being "locked up". If someone replaced the head gasket but did not inspect the cylinders, it could be that the pistons started fusing themselves to the cylinder bores. Not likely on a high mileage engine, but still possible.

 

A spun rod bearing can lock up a bottom end, and is often in the "catastrophic failure" category, meaning that the rod bolts broke and the damage is too much to feasibly repair.

 

But why do you care? You have a new bottom end, right?

 

I would never re-use an oil pump from a blown up motor without a thorough inspection and cleaning. Small bits of metal can get lodged in the pump cavity and even in the pressure relief valve. Probably better to get a new high volume pump.

 

Same goes for the oil pan and pickup tube. Those should be thoroughly cleaned as well. If the oil pan has baffles or a tray inside, use a pick and compressed air to blow out the creases where metal can hide. Pickup tubes are a bit harder to clean.

[slepe67]

18 minutes ago, Stoffregen Motorsports said:

Low oil pressure on a Datsun L motor is usually caused by main bearing wear, both on the journals and the thrust.

 

A blown head gasket is more likely a cause of it being "locked up". If someone replaced the head gasket but did not inspect the cylinders, it could be that the pistons started fusing themselves to the cylinder bores. Not likely on a high mileage engine, but still possible.

 

A spun rod bearing can lock up a bottom end, and is often in the "catastrophic failure" category, meaning that the rod bolts broke and the damage is too much to feasibly repair.

 

But why do you care? You have a new bottom end, right?

 

I would never re-use an oil pump from a blown up motor without a thorough inspection and cleaning. Small bits of metal can get lodged in the pump cavity and even in the pressure relief valve. Probably better to get a new high volume pump.

 

Same goes for the oil pan and pickup tube. Those should be thoroughly cleaned as well. If the oil pan has baffles or a tray inside, use a pick and compressed air to blow out the creases where metal can hide. Pickup tubes are a bit harder to clean.

Cool, thanks for the info. 

 

So, Datsun L20B's didn't have oiling issues, like...say...a 390 FE?

 

Yeah, I'll be running the "new" engine, was more curious as to what might be the cause on an L20B.

 

HOPEFULLY nothing came apart or damaged the head or piston cylinders so I can rebuild that block while driving the other.

 

Externally and via dipstick and coolant, everything looks normal.  No detectable leaks.  So I've got that going for me.  Which is nice. LOL

 

[slepe67]

25 minutes ago, DanielC said:

Datsun L engines are pretty much bullet proof.

I am running a junkyard L-20-B in my 521.  I did a compression test before I installed the engine, and also cranked it with an oil pressure gauge.  It had sufficient compression, and oil pressure.  I install it, and have been running it over a year now.

I did a compression test at the junkyard.  Checked very good.  Can't recall the numbers.  I guess the owner of said junkyard had the truck at his home and was going to restore the truck, never did.  The engine itself is pretty clean. I'll find out how well it runs in a couple weeks I guess!

[DanielC]

  You have probably done this, but take the cam cover off. And look.  Adjust the valves while you are in there. 

[slepe67]

3 minutes ago, DanielC said:

  You have probably done this, but take the cam cover off. And look.  Adjust the valves while you are in there. 

I have not YET, but plan on going through EVERYTHING when I get home.  All new cooling system, hoses, belts, crank seals, etc.

[Chopper Jim]

My 78 L 20B seized because the p o had engine rebuilt. and they must have used a gallon of silicone sealer. It had clogged the oil passage to the cam.

Locked up tighter than shit. Still haven't got old cam out of the old head.

 

Chopper Jim

[G-Duax]

My first L-series was locked up when I bought it due to seized cam.

The reason for that was also a dummy thinking he could rebuild it him self.

The head was warped originally, he had it cut, but neither he, nor the machine shop cut the cam tower surface to flatten it out.

I took it, machined the top surface of the head, then bored out the screwed up cam tower, and sleeved it back down to the new cam journal diameter.

Had to turn it down also, as there were few old Datsuns in junk yards in that area pull a used cam from.

[datzenmike]

There's a red light that comes on when you turn the ignition to ON. (this is to show that the light is not burned out... duh!) When the engine starts and the pressure rises above about 8 PSI the light goes out. How in the Wild Wild World of Sports could you not know if you had oil pressure or not?????????????? He's being disingenuous so you can't claim he was full of shit later. Tell him $20 and leave your number, and you'll take it off his hands. (for parts) Otherwise walk away. 

[Stoffregen Motorsports]

Shit happens. How many broken oil sender wires have I seen on Datsuns? Many. People don't always get around to fixing the little things. So calling the seller an idiot because he didn't notice low oil pressure is a stretch. Again, shit happens.

[Stoffregen Motorsports]

On 2/26/2020 at 8:39 AM, slepe67 said:

 

 

So, Datsun L20B's didn't have oiling issues, like...say...a 390 FE?

 

 

 

Nothing inherent to the L motor, not like the rusting oil galley on a FE.

[slepe67]

2 hours ago, Stoffregen Motorsports said:

Nothing inherent to the L motor, not like the rusting oil galley on a FE.

Excellent, thank you!

[datzenmike]

 

Galley. Oar powered war ship or where food is prepared on board.

 

 

Gallery. A long passage or hall, underground mine, tunnel made by mole, ant or insect boring in wood.

 

 

I found many incorrect uses of the word 'Galley' used for an oil passage in an engine. Pretty sure you know the difference but the majority of chevy owners do not.

[slepe67]

17 hours ago, datzenmike said:

There's a red light that comes on when you turn the ignition to ON. (this is to show that the light is not burned out... duh!) When the engine starts and the pressure rises above about 8 PSI the light goes out. How in the Wild Wild World of Sports could you not know if you had oil pressure or not?????????????? He's being disingenuous so you can't claim he was full of shit later. Tell him $20 and leave your number, and you'll take it off his hands. (for parts) Otherwise walk away. 

Haha.  i hear you!  I bought the truck (knowing the engine was seized) for $900.   Three yrs later,  I'm still on the fence as the whether or not I got hosed. 

 

P.O. did a lot of (dirty)work, but judging by how he seized an engine up & installed the cocked sunroof, let's jusy say Im doing a thorough QC Check before even thinking about driving it. 

[Stoffregen Motorsports]

On 2/27/2020 at 12:51 PM, datzenmike said:

 

Galley. Oar powered war ship or where food is prepared on board.

 

 

Gallery. A long passage or hall, underground mine, tunnel made by mole, ant or insect boring in wood.

 

 

I found many incorrect uses of the word 'Galley' used for an oil passage in an engine. Pretty sure you know the difference but the majority of chevy owners do not.

What?

[datzenmike]

On 2/27/2020 at 10:16 AM, Stoffregen Motorsports said:

Nothing inherent to the L motor, not like the rusting oil galley on a FE.

 

It's gallery.

[G-Duax]

Well, what ever you call it.

I call it a hole that the oil flows through........

 

Google says it's galley.

images for 'oil galley'

 

But back on subject.......

If the engine was assembled sloppily, with too much silicone,  there is one place where a chunk would kill flow to the cam real quick, and that is the press in orifice at the top of the block. It is a very small hole.

I always pull that so the galley hole can be cleaned, and then press in a new one.

[thisismatt]

It's...galley

[datzenmike]

Google isn't a thesaurus or a dictionary. It merely looks up the most common use of something even if wrong. Try oil gallery and you get the correct results. It's just sloppy language use that I call American language. It happens that words come and go and even their meaning can be reversed or changed if used enough. Awful used to mean what it says... full of awe and not terrible. If galley is used enough it will become true but right now gallery is better..

 

https://www.thesamba.com/vw/forum/archive/index.php/o-t--t-496687--.html

[G-Duax]

Mike, you say you are in Canada, I say it's actually northern Washington.......

Just because.

But the proof of the galley/gallery seems to be in your court.

I would much rather clean an oil gallery, than an old boat's kitchen.

[datzenmike]

Me too. It was a gun cleaning kit.

[wayno]

Peanut gallery 

 

 

Edited March 1, 2020 by wayno

[Stoffregen Motorsports]

23 hours ago, datzenmike said:

 

It's gallery.

Way to start an off topic argument, Mike!

 

For the past six or seven decades, it's been called an oil galley. Galley plug, galley brush...

 

Just because some next gen alt logomaniac decides to attack the word usage, it  doesn't change that fact.

[datzenmike]

Never heard it called that, course I speak English not the misunderstood mumblings of a grade three red neck shade tree '30s garage mechanic to his apprentice who passed it on to his apprentice. Look it up in a dictionary and not google. Like I said, words come and go and often their meaning changes from misunderstandings or continued wrong similar sound usage. It's obvious that galley is a basterdized, lazy, complacent and ignorant use of the word gallery.