1980 Datsun L20B z engine into 77 Datsun 620

[88z31t]

Hey guys I just bought a 1977 Datsun 620 for 1800 bucks took home found out there’s oil in the coolant so I bought a 1980 L20B engine out of a 510 but realized the head is different then the L20B in the 620 I just wanted to know if it’ll bolt on with no problems any info would be greatly appreciated! 

[datzenmike]

Yes the U67 on the '77 and all '78-'80 use the W58 head. Hmmm....  Yes it should work if a complete engine. 

 

You may need to use the 620 throttle cable mount to the carburetor base.

Use the 620 engine brackets and rubber isolaters.

Use the truck 225mm flywheel / clutch disc / pressure plate. (cars are 200mm) If it was an automatic remove the plate cap over the end of the crankshaft and fit a pilot bushing into the end.

If there is any confusion swap your 620 carburetor on. The later carbs are basically the same but may have extras that are not compatible with the earlier truck wiring or emissions.

Car alternator if it comes with it, is larger diameter and internally regulated, stick with the '77 alternator.

Car clutch fan may be different, use the truck water pump if needed.

The '80 will have an EI distributor. This can be used on a '77 to advantage but for now use the points distributor and we'll convert later. I'm off to bed...

 

 

[88z31t]

Thanks so much! Your awesome! Is it gonna mess me up if it’s a z20 block? 

[datzenmike]

The '80 A10 or HL510 should have an L20B with the carburetor on the driver's side. Check and let me know.

[88z31t]

 the carburetor is on the passenger side

[banzai510(hainz)]

This aint no direct swap for a 1st timer

sound like a Napz motor he is saying.

 

Oil in coolant could be cavitated water pump. or front cover gasket. or just bad

Edited May 14, 2019 by banzai510(hainz)

[88z31t]

Yeah there’s also oil leaking out of one of the spark plugs so I’m assuming there’s other things wrong with it then just oil in the coolant that’s why I decided to pick up that engine for 200 bucks already pulled and everything.

[datzenmike]

36 minutes ago, 88z31t said:

 the carburetor is on the passenger side

 

Then not an '80 or engine was swapped. Check the top of the block just below the head right at the dip stick. The engine size is stamped there. If swapped it may be a Z22 from a 720.

 

If Z20 then swap your U67 head, timing cover, distributor, starter, oil pan, engine brackets and the manifolds onto this block and this 'converts' it to an L20B. 

 

If you didn't see this engine running and was different than your engine you shouldn't be trying this.

[88z31t]

It says z20 on the block but I see what your sayn looks like someone took a newer head off a 720 or something and put it on there. I’m just worried that my head off the 620 might be cracked or warped.

[datzenmike]

36 minutes ago, 88z31t said:

Yeah there’s also oil leaking out of one of the spark plugs so I’m assuming there’s other things wrong with it then just oil in the coolant that’s why I decided to pick up that engine for 200 bucks already pulled and everything.

 

Oil does not leak out the spark plugs. Tighten plug or look for leak on valve cover above it. Oil in the coolant is almost impossible, they are very well separated and for good reason, water in the oil is much more likely. Only way for oil in coolant is a cracked head (very rare) or possibly the head gasket though I have never seen this. The fix could be as simple as a new head gasket. I would dump the coolant out and run just water and check it for oil later. Maybe some dough head previous owner used a dirty oily container when draining the rad???

[datzenmike]

2 minutes ago, 88z31t said:

It says z20 on the block but I see what your sayn looks like someone took a newer head off a 720 or something and put it on there. I’m just worried that my head off the 620 might be cracked or warped.

 

Cracked is very rare and no easy fix. Warped is $50 plus a gasket to fix. Hell I used a sheet of glass with sand paper on it and just pushed and pulled an L head back and forth to remove a warp. Cost $5 for the sand paper.

[88z31t]

Yes so the area around just the spark plug was leaking I looked to see if it was coming from the valve cover and it didn’t look like it was dripping down and that’s also what I’m curious about it looks to have original rad in it. But the oil is clear in the engine could the rad be broken?

[banzai510(hainz)]

I have the same issue on my 510 with oil coming from the spark plug hole.  (I say Fuck it and drive it) Its still strong just ugly to see it.

 

[88z31t]

If the heads not cracked I’d be pretty happy I probably jumped the gun on buying a new engine but for 200 I figured why not. I’d much rather use the stock engine I’ll pull the head apart this week and post more pictures then

[88z31t]

1 minute ago, banzai510(hainz) said:

I have the same issue on my 510 with oil coming from the spark plug hole.  (I say Fuck it and drive it) Its still strong just ugly to see it.

 

Yeah the truck still runs like a top! That’s why I’m so confused 

[banzai510(hainz)]

maybe flush it out and see if oil in coolant again.

 

maybe a head gasket.

 

[88z31t]

2 minutes ago, banzai510(hainz) said:

maybe flush it out and see if oil in coolant again.

 

maybe a head gasket.

 

That would be nice

[88z31t]

So that engine that I bought I think I’m gonna try it and if it doesn’t work I’ll just throw the old one back in with a new head gasket on it. Is there any upside to the z20 block

[Stoffregen Motorsports]

Some Z20 engines came with the 6" N85 rods, which are very desirable. You could use that bottom end with your L20B head to make a nice long rod 2 liter. It would be wise to do some engine math and CC the head before you get in too deep. High compression ratio is the potential problem.

[88z31t]

Somebody’s definitely messed around with the z20 so I’m not sure what’s going on with that somebody’s rebuilt it recently to. I bought it from a full service junkyard near the junkyard I work at. I’m not to keen on the z20 but the L20B  has me a little worried

[datzenmike]

The Z20 engine will not bolt up to your '77 as it is. This is why I said to swap your U67 head and manifolds etc. onto the Z20 block and make it into an L20B. 

 

Clean and flush the rad and the engine out. Do it several times. Take the  rad hoses off and the thermostat out and use a garden hose. Set the heater to HOT and flush the hoses in both directions. Someone hasn't maintained their engine and it's all rusty. Coolant should be changed every 3 years. Never run without a quality antifreeze coolant. It prevents rust. Start it up and let idle till warm and check the rad water.  If dirty drain and refill till clean. Now drive it normally and keep an eye on it. When there is no change after a few weeks refill with a 50/50 mix of anti freeze. 

[88z31t]

Awesome!!! Thanks for all the info guys I will do as Datzenmike said thanks!

[Stoffregen Motorsports]

Technically, it will bolt up, but it will be clocked the wrong direction for a Z series head. If you decide to use the Z20 bottom with an L head, the block does bolt to the trans and the clocking is correct.

 

L20B blocks are nearly identical to Z20 blocks. Cylinder wall thickness is different and some mounting bosses are different, as well as the dipstick location (which is sometimes plugged with a brass plug).

[88z31t]

8 minutes ago, Stoffregen Motorsports said:

Technically, it will bolt up, but it will be clocked the wrong direction for a Z series head. If you decide to use the Z20 bottom with an L head, the block does bolt to the trans and the clocking is correct.

 

L20B blocks are nearly identical to Z20 blocks. Cylinder wall thickness is different and some mounting bosses are different, as well as the dipstick location (which is sometimes plugged with a brass plug).

Awesome! Great to know! If it doesn’t clean out and I have to take it apart I’m gonna put the head on the z20 bottom ! 

[SPIDERSHACKOV]

Why is the Z series engine not a good fit for a truck? A cross flow head has better scavaging and for low end torque you do not want big ports or  radical cam.