720 motor identification puzzle

[frankendat]

Spent a hot afternoon at the pick and pull and have a puzzle.

Info I have - VIN JN6FD06S4DW000462 - VIN lookup confirms truck is a 1983 720 2wd King Cab

Door plate is hard to read, only legible stamped numbers are - DW 0004

Engine is a carb fed Z22 or  Z24 (pursuant to master datzenmike, Z22S motors were present from July '80 to Oct '83 build dates).

Both intake and exhaust manifolds are present, didn't have tools with me to remove. Took photos of engine and checked between the 2nd and 3rd spark plugs, no motor identification was visible (is motor ident under intake manifold??)

                                                                                                                                                                                                                                                                                                                                                                                                                                 OK, the puzzle question--With this information, can the block be identified as a Z22 or Z24 with certainty?

[datzenmike]

Try wire brush or sand paper the ID is there between the two pair of exhaust pipes below plugs 2&3

 

 

DW0004 is just part of the VIN. Should have something like 8/82 for a August '82 build date of an '83 model year.

[frankendat]

Thank you datzenmike. It is pretty tight down there. To make sure I was looking in the right place. Standing at the front of the truck, facing the grill, on the exhaust manifold (right) side, I should sandpaper/wirebrush, below plugs 2 and 3 (which are the FIRST pair of plugs encountered, if looking from the front of the truck)                                                                                                                                                                                                                                                                                                                                                                                          I brought rags and wiped this area, but no sandpaper or wirebrush---oops

[frankendat]

So, that other info won't confirm it, it's back with wirebrush or bust?

[datzenmike]

Not exactly. The side described is always from the seated position in the vehicle, so left side is the driver's side. The driver's or exhaust side. There are 4 plugs, skip the first one and look down between 2 and 3 to the top edge of the block. There are a few other ways but this is definitive and easier.

[frankendat]

Thanks for squaring me away. The pick and pull wants 90 for the bare block  250 for the block crank and pistons. That seem high to you? I can't see the pistons being anywhere close to spec, so they're worthless, but the rods and crank should be saveable. Still, a 100000+ motor, stored outside (hood open, carb, no air cleaner) machine shop work is a given. I haven't bought anything from pick and pull for a while, is this new "normal"?

[datzenmike]

You'll get it home and have to pound the pistons out with a 2x4 and sledge hammer because the cylinders were full of rain water. A complete non running but rebuildable engine (not stored outside and full of water)... maybe $100.

[frankendat]

5 minutes ago, datzenmike said:

You'll get it home and have to pound the pistons out with a 2x4 and sledge hammer because the cylinders were full of rain water. A complete non running but rebuildable engine (not stored outside and full of water)... maybe $100.

 

Exactly! It is nice to know that I'm not completely out of touch. I thought $50 for a non running engine without carb/alternator (I would even let keep the head, intake and exhaust manifolds). But, I'm cheap budget conscious, and things keep getting more expensive...so, $75 and I'd bitch about it. BUT $90 for the empty used block and $250 for block crank and pistons???!!

 

If I go back and confirm it is a Z22 block, then I'll talk to somebody higher up the food chain before bringing out my tools---That's right "tools"  these prices are when you disconnect it and pull it out of the truck (They will provide an engine hoist, if you get there early and snatch it up)

[datzenmike]

What are you looking for? One to rebuild?

[frankendat]

I am seriously considering it. I looked for a datsun 4x4 to steal the parts for my project rig. The ones I found were either too far away or priced more than I would pay. I've been looking close to a year and my project fund keeps getting attacked. The reason it has been hard is I am not a fan of the NAPZ. Oddly, I like motors that create horsepower and torque at lower rpm, so the performance curve of the Z24 is great. But, the Z24 is too physically big for my project. I have been reading Ratsun much and the truck motor Wayno built was intriguing. Again, bigger than I need but the Z22S with an L20B head and 87mm pistons caught my eye.

 

I have researched much, but perhaps there is something I'm missing----A carb fed motor about the size (or smaller) of a L16, 75-100hp, 100-120 ft lbs, 2500-3500rpm cruise, 30mpg (not turboed) The motor that comes really close (and exceeds some  requirements) is the Z22 with an L20B head.

 

In truth, a bone stock L20B would suit me fine, but these motors are old and I have to assume need rebuilt-- complete rebuildable (not stored outside) are $400 or more (Rebuilt ones are priced well above 4 figures) Doing most of the work myself, I think I should be able to buy and rebuild a no frills motor for $1000. There is no way that is possible starting with a $400 stored inside rebuildable.

By opening up my search to include some Z motors, I have more opportunity to find bargins

[frankendat]

It is the two distributor set up on the Z24 that makes it physically troublesome for my project (and I don't like the NAPZ head)

 

While still bigger than I need Jason Gray's notes on Ben Pila's  Datsun Frankensteins caught my attention....." Instead of using a L20B block, start with a Z22S block and bore it only +2mm for thicker cylinder walls or use the Z20S block with thicker siamesed walls. This 2.4L is probably the ultimate street-torque L series engine...The very low rod to stroke ratio of 1.52:1 is well below desirable range so will limit high RPM effectiveness but make for great low/midrange torque."

 

OR  another way to answer your question, yes, I am looking for a Z22 for rebuild 🙂

[datzenmike]

The Z22 block is identical to the L20B, the Z24 is the same as the Z22 but 3/4" taller than it.

 

 

 

This is my Z24 with L20B head on it. Compression should be just over 9.

[wayno]

I am sorry Mike, but I believe your last post is wrong, the L20b, Z20, and Z22 are the same, the Z22 block is exactly the same height as an L20b/Z20, if it wasn't we could not use the L20b front cover on the Z22 with an L head to make an LZ22.

The L20b is taller than an L16, and the Z24 is taller than the L20b/Z22.

[datzenmike]

Good catch. I usually say the L20B is 3/4" taller than the L16/18. Carry on

 

BTW I used the Z24 timing cover and put an L head right over it. There was only one corner that was close to not sealing and a little JB took care of that. Naturally you can't use those small bolts but it only has to seal fumes and oil splash in.

 

 

Chain needed two links

 

[frankendat]

Your pictures are outstanding, as always. A Z24 with an L20B head, would open up the market (I have come across a number of "bargain" Z24's) What kind of performance numbers are you getting? Mpg? Does it putt and rev like a tractor? (I like tractors)

 

Is the motor is a stock Z24 with Z24 rods, Z24 pistons, Z24 cam etc, and a standard (readily available) L20B head? Also, no problems with pump gas? If pump gas will cause problems, is there a different L20B head that lowers compression?

Edited April 8, 2020 by frankendat
more info

[wayno]

It's a stock Z24 block/rods/crank/pistons with an L head/cam, but there is more involved than just getting parts and putting it together if using a Z22 block, if you can find a Z20S block nothing needs drilled, but then it is just an L20b unless you punch out the block.

I used Z22 blocks and I drilled 7 holes the blocks for coolant passages into the head, I heard if you don't drill the holes the head gets hotter on that side and that could possibly cause head gasket issues, it is kinda hard to find Z22 blocks without cracks around the middle head bolt, anyway I made my head gaskets out of the Z24 head gasket, it is a pain in the ass, but Haniz has posted about where to get 89mm head gaskets, I will go that route next time.

The Z24 in the truck is a good engine for the 720, it is not the greatest engine to work on, but it has the torque to move the truck, it's just not a race truck with that engine, it likes 60mph, at least the one I put in a 1970 Datsun 521 liked 60mph, my work truck with the LZ23, super head, and dual SUs will kick its ass on the freeway, my 521 work truck weighed 3400lbs at the time I built my first LZ23 and it pulled hard all the way to the mid/high 80s and it continued to accelerate till I broke the speedo needle off, but one has to keep in mind that it cost me a lot of money to punch the block out to 89mm, it also cost money to make the super head, dual SUs also cost money, you also will have to convert over to an L block transmission, you really have to want it, it would be so much easier to just put a running Z24 engine in the truck.

[datzenmike]

The Z head doesn't breath very well and no way to fix. I haven't finished it yet but the L head breaths very well. If an L20B makes an easy 95 HP then increasing the displacement by 20% would increase the HP by 20% or 114HP.

 

One day I'll put it in my 710 which has R-1 bike carbs, and L16 cast exhaust. I also have an Isky cam laying around. Byron on the Realm had an LZ22 with cam and side drafts and it was 135 HP. Have the dyno chart somewhere.

[frankendat]

Wayno, Datzenmike, thank you both for taking the time to reply to this thread.

 

It is unfortunate that more is involved than part swapping to mount the L20B head to the Z24. I am guessing you are referring to the fine details in adding links to the timing chain and valve cover difficulties. While unfortunate it is not too  tragic, as I have said, I require no more performance than can be supplied by a weber fed (single) L20B. Difficulty obtaining a L20B, along with the realization that, to be reliable, any, affordable 40 year old motor should have machine work, prompted exploration into the frankenstein motors. But, any frankenstien motor, would need to incorporate standard, available parts (oversized or undersized to compensate for wear, notwithstanding)

 

Am I correct in thinking a Z22 block, machined to compensate for wear, with Z22 pistons L20B cam and head will build a strong reliable motor (LZ22) equal to or better performance than a L20B, equal to or better mpg than a  L20B, equal to or better reliability than a L20B? As I understand an open  U87 head brings compression in the high nines. It is also my understanding that high of compression should run at least premium gas. I run premium for hwy trips, but it would be nice not to have to run it. For an LZ22 what L series head might lower compression a bit?

[wayno]

OK, I built an LZ23, it is a Z22 block/crank, I had it bored out to 89mm to except stock Z24 pistons which are dished, I had basically a 219 head made(closed chamber) out of a W53 head(hardened seats/280Z valves), and I had the intake ports ported out to match a 1.5" dual SU manifold, it has a stock L20b cam, this setup put me at around 8.9 to 1 compression ratio, I eventually had to re-curve my distributor because I run regular gas in this engine and it still knocked slightly timed at 0 degrees before top dead center before I re-curved the distributor.

Everything depends on what pistons you have, if they are dished you may be able to run a closed chamber head, if you have flat top pistons then a U67 head or some other open chamber head like the A87 open chamber head or the W58 open chamber head but it has round exhaust ports, but again I think the CR ratio is going to be sorta high, you would have to ask Dmike about them numbers.

When I had an L20b I got around 17/18mpg going 70mph, when others drove my truck 60mph they got around 23mpg, when I put my LZ23 in the truck I got 23mpg going 75+mph, but this was an empty truck on the freeway.

As for the reliability of my L block/LZ block engines, I have had no issues with my engines other than stuff that others have done before me like wiring and choice of transmissions, but all my heads have hardened seats, and my work truck with the LZ23 has got the shit beat out of it daily for 9 years now, and for 15 years before that with the L20b I had in it, in my opinion they are not strong enough engines to tear themselves apart as long as one keeps oil and coolant in them when driven normally, if you drive them like you stole them they are eventually going to break.

[datzenmike]

As wayno pointed out the L20B, Z20 are identical blocks even using the same crankshaft. The Z22 is still the same basic block but with a larger bore and a longer stroke crank and uses L20B rods still. You could even bore an L20B out to the Z22 size and the Z22 to Z24 size but the cylinder walls would be thinner. The Z24 is, again, the same basic block as the L20B BUT, the bore is even larger than the Z22 and the cylinders taller by 2cm or 3/4" to compensate for the, again, increased stroke and longer rods. Should be noted that Z22 (or even an L20B block can be bored out to Z24 but cylinder walls are thin) and instead of Z24 pistons, KA24E pistons can be used.This will have a much higher compression.

 

About compression. Higher compression will raise the temperature of the combustion chamber making it more likely to set off the gas air mix when you don't want it to... called pinging. The cure is to run a higher octane gas which makes the gas less sensitive to self ignition. Generally a higher compression is more efficient because the combustion chamber area will be smaller than a lower compression engine. A smaller combustion chamber won't absorb as much heat and the heat saved goes into doing more work turning the engine. On top of this a tightly compressed gas/air mix will explode and burn faster reaching higher cylinder pressures than a low compression engine, pushing down on the piston with more force. Now that said if you capture more of the gasoline's energy and put it to work moving your vehicle it's very possible to increase your mileage enough to more than pay for the additional cost of having to rum premium or high octane gas. It seems harsh to be paying 35 cents more per gallon but if  you get 20 MPG on regular, but get just 10% better (22MPG) with your high compression engine on premium they both cost $0.13 cents per mile to drive  

 

An LZ engine mixture of parts is great if you cannot locate a complete engine to rebuild. You could call them 'stroker engines'

[frankendat]

Thank you for responding Wayno and Datzenmike,

Wayno I read your LZ23 build a while back and it is certainly a beast. I pulled a little better mpg numbers when I had a stock 78 620 in college, low 20's in town, 25 on the highway if I went the speed limit, (which was 55 or 60, 65? back then). I read here and other places on the internet (internet information is, as you know, certified 100% accurate) of slightly modified L20Bs e.g. pistons, rods compression increase and such, getting 30mpg and some extra torque or horsepower to boot. Granted, the monster LZ23 you built traded some mpg and longevity for all that power, but I would be fine with lower HP and torque numbers. However, if I am understanding the information provided by you and datzenmike, if one is willing to read, turn a wrench,and pay for some machining, the 30mpg frankenstien with a little more pop than a stock L20B can certainly become reality.

[datzenmike]

My stock (other than R-1 carbs) L20B 5 speed gets 28-30 on long trips to Canby. That's US gallons. Generally the larger the displacement the worse the mileage. Often a larger displacement EFI will give better mileage than a smaller carb engine.

[frankendat]

Pick and Pull update:  The pictures and instructions provided by datzenmike, made discovery of the engine block data easy (on earlier attempts I was scraping in the wrong spots).

Now, running the VIN number through the online database, confirmed Pick and Pull's identification of a 1983 Nissan 2wd, BUT, the numbers on the engine block are Z20 40124, I triple checked the numbers with my head lamp  (isn't that too many numbers??) There was certainly a 0 after the Z2.

Thoughts?

 

Edited April 9, 2020 by frankendat
mistake

[datzenmike]

It's an '84-'86 Mileage option Z20 (carburetor) engine. Has the small combustion chamber W04 casting head with 9 compression and a knock sensor and electronics for ignition retard in response to pinging, long rod flattop pistons, 240mm clutch, 5 speed and an insane 3.364 differential. Was an option for fleet trucks aimed at higher mileage.

 

VINs are ok but engines can be swapped. This will also have a tag under the passenger side hood hinge on the inner fender saying the same thing.

[frankendat]

Excellent, thank you for the fast response. Is this a good candidate for a rebuild with a L20B head? Are there hard to  find parts on this engine worthy of salvage? Also, how do you decipher the build date from the numbers I provided?

 

Edited April 9, 2020 by frankendat
made more sense when edited