720 motor identification puzzle

[datzenmike]

If you were to put an L20B head, like a U67 or W58 on the flattop pistons would raise the compression to about 9.95. The rods are six inch rather than 5.75" and some would consider this a long rod engine which is rev happy. You would probably run high octane premium gas.

 

The VIN would only be the model year while the actual build date (month and year) is on the driver's door jam and much more accurate for finding parts as things often change during the model year.

[frankendat]

Thank you datzenmike, I was inquiring about the numbers on the block. I thought from the block is identified by the first 3 digits, in this case Z20, then there is a blank space, followed by 40124. Is there a way to determine build date from the 40124?

[frankendat]

Additionally, as I seek high torque at low-mid range rpm, should I pass on salvaging this motor?

 

[datzenmike]

The engine may have been built long before it was put in the truck. They were an option starting in Jan '83 so no older than that.

 

Not the best for torque. You want something with displacement, Z22 or Z24 even better.

 

What is this engine going in again? What year 720?

[wayno]

Yea that engine was awesome till today, I lost a head gasket today, #4 cylinder puked coolant out when I removed the spark plugs and turned it over.

I have a fresh LZ23 in the back room with a super head with 44mm intakes, I will likely put that engine in as I don't have a replacement head gasket for it made right now and I want to buy one of them 89mm L block head gaskets Hainz talks about instead of making one out of a Z24 head gasket.

I have not decided yet, maybe I will put the 1980 Datsun 720 turbodiesel into work mode.
 

Sounds like you need a Z24, they are torque monsters.

Edited April 9, 2020 by wayno

[frankendat]

Thank you both for your help. The Z24 is too big for my application. I am willing to pass on this pick and pull find if it is not great (They are pricing it high for what it is) What I was thinking (subject to modification as information and part availability present) ----Pull this block, the rods and crank (if they check within acceptable specs) This block that sat outside should be machined, so have it bored to 87mm, use either Z22 pistons or milled VG30 pistons (I only entertain the milled VG30 pistons, because I have access to a mill. I would like your opinions on the gains from using milled VG30 pistons, instead of Z22 pistons.) I am unsure if the addition of a Z22 crank would be beneficial, or if the Z20 crank will suffice.

I remember reading the 720 economy blocks are well suited for boring, but I could be confused.

It seems like I am basically building a Z22 with an L head, so would it be simpler/cheaper to keep looking for a Z22 block?

My final bit of confusion is rod length. The long rods of this particular pick and pull motor, seem to be an great feature for high rev motors. But, the balance and such must make them good at low and midrange rev  as well??? Would shorter rods an not milling the VG30 pistons create a lower reving, higher torque motor? (87mm is still a bump in displacement for a Z20)

[datzenmike]

1 hour ago, datzenmike said:

 

 

What is this engine going in again? What year 720?

 

I assumed you needed a high torque engine. What is this project engine going in??? 

[frankendat]

Sorry datzenmike, I got caught up in the pick and pull motor and missed that one.

It is going in a little Suzuki 4x4

[wayno]

Now I understand why you don't want a Z24, I thought it was for a 720.

The Z20 block is sort of a sought after engine because of the long rods, I know a few people looking for a Z20, but they are likely too cheap to pay much for one, the rear gears that mileage option had are very rare, I have them in both my diesel trucks as my diesel engines have the torque to turn them gears, it took me almost 6 years to find two of them, and both I stumbled into at a wrecking yard, I got lucky.

If you can find a good Z22 without cracks in the block I would go that route, I would also look for the 200SX with a Z22E block, that is what I made my first LZ23 out of, you can also sell the intake to recoup some of the money you paid for the engine.

[datzenmike]

Oh yeah I remember now.

 

How is it 'too big for your application...'???? The only difference between a Z24 and the earlier Z20 and Z22 is that it's 3/4" taller. Uses the same head, distributor, water pump, main and rod bearings. It's the same engine except the larger displacement inside.... and the 3/4" taller block. If planning 'mudder' tires you'll need the higher torque.

 

 

 

[frankendat]

The dual distributors make the engine wider. An L20B (without power steering and with a modified alternator bracket) is long and skinny (relatively). I can work with height, body lifts, hood scoops, low profile oil pan with remote filter, are no trouble (if necessary). Width, is big trouble. And, I dislike the thought of working on a Z24, primarily, because I am unfamiliar with it. You are making a good case for it. It is true I like low rev high torque tractor motors. My 78 620 L20B ran and ran, I treated it poorly, and still it ran (I am much more appreciative of working vehicles as I age)

 

Afterthought: I vaguely recall a 4 plug single distributor Z24. Would that be the same width as an L20B (If it exists, not talking about an LZ23)

Edited April 9, 2020 by frankendat
afterthought

[datzenmike]

If you are putting an L head on either a Z20/ Z22 or Z24, the intake will stick out farther than the Z series distributor anyway. With an L series head on the block it will use L series engine brackets that lean over to the right side 12 degrees from vertical as well, pulling the intake and exhaust away from the left side.  You will have a stroker L20B when done that is 2.4 liters inside but a mere 3/4" taller than an L20B outside. Cake.... and eat it too.

[wayno]

The simple answer is, the only difference between a Z24 block and a L20b block is the Z24 block with an L head will be 3/4" taller as you use everything on the L20b except the block, L head, L distributor, L intake, L exhaust, L engine mounts/brackets, L oil pan, L valve cover, it's an L block except it is 3/4" taller than an L20b.

It is a little more complicated, I don't know if the Z24 block needs to be drilled like the Z22 block(coolant passages), it also needs 2 extra links in the timing chain, and the Z front cover needs to be modified so it don't leak fumes/oil, but in the end fitment wise it is 3/4" taller, everything else is exactly the same as an L20b.

[frankendat]

Datzenmike, Wayno, your counsel is valued. With this information, there are more options and hopefully  opportunities. The next step is to find a "right priced" engine and begin. Whether a stock L20B, Z20,Z22 or Z24 and give it a refresh rebuild maybe mix match some parts. More probably than not, I will run potential purchases by the ratsun community and seek your blessings before parting with my hard earned.

 

Another question for which the search function is failing. I was under the impression that a later model 720 distributor could be used as an electronic "matchbox" type of distributor on a L series. Is this true or bullshit and if true could you point me in the direction for the specific details?