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ValveFloater

L20B w/U67 and rebuilt Z20 engine.

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Here is a great eye roller for you!

 

 I have a fantastic running original 1979 L20B with W58 head with 69k original miles. It is installed and runs like a sewing machine. 

 I recently acquired a used, fully complete L20B with a U67 head with all accesories and transmission still bolted. It looks like a pull out. Oily old engine in unknown condition.

 Along with this I got a Z20 longblock that looks freshly rebuilt. Under the wrap it has fresh paint, new freeze plugs, valves and timing chain look to have never had gas/fire/oil. My guess is it came from a machine shop then mothballed. You could use it for a plate for a grilled cheese sandwich it is so clean.

 

 I have a 620 which I plan on owning forever!

 

 Question, should I????

 

 Option A: Shrink wrap it and store it for a rainy day.

 

 Option B: Sell it and use the money for 620 cosmetics.

 

 Option C: Take the U67 head to a machine shop and stick her on the Z20 for a engine upgrade. 

 

 Open for Option D suggestions.

 

I know this sounds like I am 17 years old and inherited my uncle's Datsun junk but I am froggy and prone to leap.

 

 WWDMD (WHAT WOULD DATZEN MIKE DO?)

 

 

 

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Bolt a starter to the L-20-B, do a compression check on the engine not in the truck, and while doing that, get a 1/8 BSP to 1/8 pipe thread adapter, put an oil pressure gauge on the engine while cranking it.

May as well do a compression check on the engine in the truck, and check it's oil pressure.

Take the cam cover off the L-20-B engines, just look at the inside of the engines.    That will give a pretty good isea of the condition of both L-20-b engines.   69 K miles on a Datsun L-20-B engine is not a lot of miles.

 

Rule number one.

Do not fix what ain't broke.

Rule number two

Do not mess with your transportation, see rule number one.

 

I believe the Z20 engine tilts the wrong way to fit the L-20-B transmission.  You also need to get the intake manifold and carb, or fuel injection, and exhaust for the Z20 engine working in your 620.  

 

I know some have put a L head on a Z block, and installed that engine in place of a L engine, but this is usually done with a Z22, for a displacement increase.  I am not sure if there is an advantage of using a Z20 bottom end over using a L-20-B bottom end.

 

A reliable Datsun is a stock Datsun.

 

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28 minutes ago, DanielC said:

Bolt a starter to the L-20-B, do a compression check on the engine not in the truck, and while doing that, get a 1/8 BSP to 1/8 pipe thread adapter, put an oil pressure gauge on the engine while cranking it.

May as well do a compression check on the engine in the truck, and check it's oil pressure.

Take the cam cover off the L-20-B engines, just look at the inside of the engines.    That will give a pretty good isea of the condition of both L-20-b engines.   69 K miles on a Datsun L-20-B engine is not a lot of miles.

 

Rule number one.

Do not fix what ain't broke.

Rule number two

Do not mess with your transportation, see rule number one.

 

I believe the Z20 engine tilts the wrong way to fit the L-20-B transmission.  You also need to get the intake manifold and carb, or fuel injection, and exhaust for the Z20 engine working in your 620.  

 

I know some have put a L head on a Z block, and installed that engine in place of a L engine, but this is usually done with a Z22, for a displacement increase.  I am not sure if there is an advantage of using a Z20 bottom end over using a L-20-B bottom end.

 

A reliable Datsun is a stock Datsun.

 

 

 

Mr Daniel, this actually brings up something I have been wondering.  When you suggest doing a comp check on the motor not in the truck, how would you suggest to do this.   I have one I want to do this on, but have no bench unit or what not to secure? the motor.   The motor I would like to do this on is on tires under my cherry picker.  Would it be fine to do a comp test like this?  

 

Its kinda hard for me to type my thoughts out if this is confusing.  

 

Thanks

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Keep your W58 head L20B in the truck and running.

 

What is the L20B with U67 head out of?

 

 

The L20B and Z20 share the same crank and the blocks are almost impossible to tell apart they are that identical. By using all the L series timing gear, chain guides, oil pump and distributor, oil pan and head you can convert it into an L20B. The last thing is the L series engine brackets that will position the engine tilt properly to bolt up to an L series transmission. You are basically just exchanging the Z20 block, rods, pistons and crankshaft for the L20B block/rod/pistons/crank. 

 

The Z20 rods and pistons are different from their L20B counter part. This is a 'long rod' engine and has flattop pistons. The compression with a U67 open chamber head is just a hair under 9.941. That's going to need high octane gas. I would open up the combustion chamber, removing the shrouding around both valves to improve breathing and grinding away any lumps or bumps that are cast in.  Increasing the combustion chamber size will lower the compression.

 

Bolt the L series transmission to the engine on the tires and fit the starter. You are not starting the engine only spinning it over to get a compression reading. Normally the engine would be warm so if the readings are good, they are actually even slightly better.

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"The motor I would like to do this on is on tires under my cherry picker.  Would it be fine to do a comp test like this?"  

YES!  The engine should have oil in it. 

 

Here is a picture doing a compression test on an engine.  This picture is from 2013, I do not remember exact details.  I think the edges of the oil pan were set on 4x6 blocks, and I used a cable hoist to hold the top of the engine, maybe. 

You need to bolt a transmission to the engine.  The only thing the transmission is for is to hold the starter.

CompTest.JPG

 

Bolt a starter to the engine and transmission.

Get a fully charged battery.  Hook a negative battery cable from the negative battery post to the engine somewhere.  I just use the stock bolt in the cylinder head behind the fuel pump on a L-16.

Hook the positive battery cable to the large positive connection on the starter, with one wire from a remote starter switch.

Hook the other wire of the remote starter switch to the small 1/4 spade terminal on the starter solenoid.  Two battery cables, and two wires from a remote starter switch.  That is all you need to crank an engine for a compression test.

Edited by DanielC
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On 12/16/2019 at 6:00 PM, DanielC said:

I know some have put a L head on a Z block, and installed that engine in place of a L engine, but this is usually done with a Z22, for a displacement increase.  I am not sure if there is an advantage of using a Z20 bottom end over using a L-20-B bottom end.

 

A reliable Datsun is a stock Datsun.

 

Z20 engines did come with 6" N85 rods. There are so many engine combos that can be built using the Z20 block and those long rods. Most require custom pistons, but if you find the right head, it is possible to bolt it onto the Z20 bottom end and have a long rod 2 liter with streetable compression.

 

Yes, reliability comes in many forms, but custom engines can be built to be reliable. Even more so actually. Think piston rings - modern rings are much stronger than old tech cast rings, which can break if the engine pings too much.

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Well shit.  I will be getting doing the test this weekend.  I had been doing searches in forum and out looking for ways to test it on the floor.  I knew it wasnt going to be running but I am that guy who then has to tell the tale of how he did something stupid and something happened.  Luckily, the motor is till hooked to the tranny, just need to find two bolts for the started as I stole them to put on my hardbody.  Also cant remember if the trans is in neutral, but I think I know where the shifter is at.  This in theory should save me from pulling the head for no reason.\

 

 

Sorry to threadjack op.  Got all bonered up.

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I build these engine stands, only takes a few hours, this one has wheels and I can tow it with my tractor, but you only need to have the mount brackets sticking up and a block of some kind for the transmission to rest on.

DSCN7448.jpg

 

I even make them stands with radiators so I can run them.

009.jpg

Edited by wayno

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If the engine is out, then it matters very little if the transmission is in gear or not. You're only spinning it with the starter to get the compression.

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Well, ran my comp test.

 

1-160

2-160

3-150

4-180

 

 

All plugs out and carb wide open.  Its hard to remember exactly but all I can remember is it would not pull off idle.  Think I will clean it up, regasket it and drop it in the 521.

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Just I guess to keep this here, can someone verify my gasket list?

 

 

Valve cover gasket

Thermostat housing and cover gaskets

Fuel pump gaskets

Timing cover set with front main, oil pump, and distributor gasket in set

Rear main

Intake gasket

Oil pan gasket

7 40mm brass expansion plugs

Exhaust down pipe gasket

 

Please let me know if I am missing anything.  With the exception of the freeze plugs, it all ships from one place off rock.  Just trying to cross my t's and dot my lower case j's.

 

thanks

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