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1981 Datsun 720 - What engine?


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#1 650savag

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Posted 31 January 2009 - 08:22 AM

Hey guys, I spotted a pretty good looking 720 yesterday near my home and I think it is a 1981. I have a 1978 620 and a 1980 720 and it looks almost identical to my 720. It's a kc and it is in a locked up, fenced in area. I got a contact number to find out if it is for sale. Don't look like it has been moved in a while. I haven't called the owner yet and I was wondering if anyone (maybe Datzenmike) could tell me if all the 1981 720's had the Z22 or NAPZ engine or did maybe, some of them have the L20b? My 1980 has the L20b in it. How does the Z22 compare to the L20b engine as far as dependability and long life? Thanks for all the help. Dan
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#2 Nissan_Boy85

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Posted 31 January 2009 - 09:10 AM

I'm no datzenmike, but I do believe that some of the very early 80 720s had the L20s. Otherwise all I'm aware of is that the 720s had the NAP-Zs.

The 81 720s either had the Z20 or Z22 (again, not sure)

NAP-Z is (as far as I know again) just a name for the Z20, Z22, and Z24. If I'm wrong, TEACH ME MIKE! :lol:

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#3 datzenmike

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Posted 31 January 2009 - 09:22 AM

'80 model year (06'79 to 06'80) is the L20B like you have, the '81 and '82 model year used the Z22. HP wise they are comparable but the Z22 has more low end torque for pulling the increasingly heavier (4X4) 720. The block is almost identical to the old L20B but with increased bore and stroke and is oriented in a more vertical position. The big difference is in the new cross flow NAPS Nissan Anti Pollution System head. I like to call it the Nissan Anti Performance System. Everything about it was designed for low emissions at low driving speeds. It's a great little motor, and easily equal to an L20B, and then some, but the head design does not lend itself well to high RPM breathing so power is limited from a performance standpoint.

The Z20S (carb) was offered as a Mileage Option engine from '84-'86. It was a (misguided) attempt to us a smaller engine with 9.5 compression and ridiculous 3.364 rear gears to offer improved mileage... maybe it did but the performance was sucky as you can imagine.

Edited by datzenmike, 31 January 2009 - 09:29 AM.

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#4 650savag

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Posted 31 January 2009 - 01:51 PM

Thankxs Nissan_boy and datsunmike for the good info and tech data. Is it true that all these engines have the 8 plugs and 2 coil system? Is this a plus or not? Dan
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#5 Nissan_Boy85

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Posted 31 January 2009 - 02:41 PM

NAP-Zs (Z20/Z22/Z24) all have 8 spark plugs and 2 coils. One coil for ignition, one coil for exahust.

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#6 Rubberman

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Posted 31 January 2009 - 03:51 PM

I was at the yard the other day and there was a 1980 210 wagon that had a Z20 motor and it only had 4 sparkplugs. Hey datzenmike, how would that motor do in a 620 compared to the l20?

#7 datzenmike

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Posted 31 January 2009 - 04:10 PM

All 720 Z motors were 8 plug. The first year ('80) 200sx had a 4 plug head outside of California but switched to 8 plug about 08'80.(I think) Canadian Z20s were all 4 plug.

Both plugs fire together. With two ignition sources the fuel is burned twice as fast so the ignition timing can be retarded but have the same power. (less emissions) Also more EGR can be used and leaner mixtures. However you slice it, two plug are always better than one.
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#8 datzenmike

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Posted 31 January 2009 - 04:15 PM

I was at the yard the other day and there was a 1980 210 wagon that had a Z20 motor and it only had 4 sparkplugs. Hey datzenmike, how would that motor do in a 620 compared to the l20?


Below the head the Z20 and L20B are practically identical. The L head has better breathing at higher RPMs and would respond to performance mods better than the Z20. In stock condition they would be about equal with the L20B having a slight edge.
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#9 Rubberman

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Posted 31 January 2009 - 04:27 PM

Ok. scratch any ideas about a Z20. Still just gonna soup-up the L20.

#10 650savag

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Posted 31 January 2009 - 05:16 PM

OK, so I just talked to the owner on the phone and he don't know a lot about the truck. He bought it from a lady in the small town where he lives. Her husband had recently passed away. That was about 6 months ago. He said he got it started and drove it to the lot where it is now. He was going to work on it and fix it up but says he don't have the time now. He don't know the yr. model but I know it is an 80 or 81. He said he thinks it is an auto trans. He could not tell me what all was wrong with it, except he planned to do some body work on it and paint it. I didn't think to ask about the milage but he probably would not have know that either. He asked me what I thought it would be worth to me. I did not give him an answer without checking it out. From looking at it through the fence, I saw only a little rust in the usual areas, and one fender had a small bent place in it. Other than that the body looked good. It's a KC. You guys got any ideas what I should offer, if it is in good mechanical condition? Thanks, Dan
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#11 datzenmike

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Posted 31 January 2009 - 06:40 PM

Depends what you want it for. The '81 would likely swap a lot of body parts. The engine could be put into your '80 but you would need a 5 spd for a Z engine. If it's an '80 then everything will swap.
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#12 Llittle_Llama

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Posted 31 January 2009 - 06:46 PM

500 bones?

EDIT: offer 400 plus skibs 4 speed tranny :lol::lol::lol::lol:
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#13 HRH

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Posted 31 January 2009 - 07:45 PM

If it's an auto, stick as far away from it as you can. They weren't built well back then, sucked hp, and didn't last too long. In short, a boat anchor you very likely will have to replace. But if you have a spare 5 speed, that wouldn't be too hard.

Yes 81 should have Z22, make sure you don't get screwed and get one with a replacement motor! (Z20 like I have, 84-87) Two plugs are better than one, but NAPZ heads suck for breathability. Stock heads usable rpm is about 4500-5, even though the tach says 5500. Not that they can't get up that high, they just don't make any more power.

#14 RatVonDude

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Posted 11 March 2016 - 04:57 PM

All 720 Z motors were 8 plug. The first year ('80) 200sx had a 4 plug head outside of California but switched to 8 plug about 08'80.(I think) Canadian Z20s were all 4 plug.

Both plugs fire together. With two ignition sources the fuel is burned twice as fast so the ignition timing can be retarded but have the same power. (less emissions) Also more EGR can be used and leaner mixtures. However you slice it, two plug are always better than one.

 

I hope so, broke down and took my z22 720 to mechanic. He didn't give me any blessings. Here we go again.    



#15 weldingrod

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Posted 20 February 2017 - 06:55 PM

Z20 2wheel drive, Z22 4 wheel drive.



#16 datzenmike

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Posted 20 February 2017 - 08:09 PM

1980............... L20B 2 and 4 wd, SD22 2wd

1981-1982...... Z22  2 and 4 wd, SD22 2wd

1983-1986.5... Z24 2 and 4 wd..... Z20 and SD25 2wd and 5 speed only.

 

There were no automatic 4wd or Z20 or SD22/25 diesels..

There were no 4 speeds available after '82 with any engine.

All Z24 and Z20 were 240mm flywheel.


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#17 RaZorback

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Posted 03 March 2017 - 04:50 PM

I just bought a 1981 Datsun truck. I read past post and I see that someone says the 4 speed stick wasn't available then. The one I bought is a 4 speed and the top of the engine says Nissan z. How do I find out if the motor is original or not. It is similar if anything. The guy I got it from says it the same as the stock motor.

#18 Lockleaf

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Posted 03 March 2017 - 04:55 PM

4 speeds were available, though uncommon. The Z motor is correct for your truck. Probably a z22 engine.

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#19 datzenmike

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Posted 03 March 2017 - 05:16 PM

1980............... L20B 2 and 4 wd, SD22 2wd

1981-1982...... Z22  2 and 4 wd, SD22 2wd

1983-1986.5... Z24 2 and 4 wd..... Z20 and SD25 2wd and 5 speed only.

 

There were no automatic 4wd or Z20 or SD22/25 diesels..

There were no 4 speeds available after '82 with any engine.

All Z24 and Z20 were 240mm flywheel.

 

Actually October '82 was the cut off for the four speed. This is about 4 months into the '83 production model year when the Z22 was retired and the new Z24 was introduced. Your '81 most certainly could have come with either 4 or 5 speed. Look on the engine tag under the passenger side hood hinge on the inner fender. It's a stamped aluminum tag about the size of a credit card.

 

720Large2.jpg

 

This happens to be an '82 tag I imagine the '81 is similar. Bottom line (above) is FS5W71B. This is for the 5 speed. Yours may say F4W71B, that's the 4 speed and what was installed by the factory. Possibly it had a 5 speed that broke and was replaced with a 4 speed. Lots of things get done to keep a vehicle on the road over 35 years.

 

Just above the FS5W71B is the engine size Z22 or 2.2 liters, but again anything could have been swapped so the only positive way to know for sure is to look between the two exhaust pipes that come out of the head. Use a flash light. Look at the #2 spark plug and down onto the block, there is a flat surface and the engine size is stamped there.

 

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#20 RaZorback

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Posted 03 March 2017 - 05:27 PM

Ty, I will check Tomorrow. It's a rust bucket but the engine and transmission is in good condition. Runs great. But alot of TLC involved. Floor and all rusted through. Couldn't beat the price for engine and trans if anything