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Big Red 76 620 L20b w/5 spdl20b

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Hello everyone. Been around Datsuns for quite awhile mainly roadsters and trucks.

Just acquired big red and want to make it a modern day drivable vehicle. Swap brakes drums for disc at least on the front to begin with.


Some of you may know my wife Robin, aka Datsungirl. She got me involved with the roadsters. We were members with NWDE BUT moved on and sold the roadsters.


Looking forward to tricking this truck a bit. Saw on here somebody had a kit for electric door locks. Give me a yell please.

Looking forward to drawing from the knowledge on this site.


Good news. The compression checks at 175 to 180 on all cylinders.


Pics attached.




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Finally got on here. Not much on the email thing. Any way.....


We were planning on driving her for awhile but the clutch started making  noise. So I've started tearing her down.

The truck is in great shape w/minimal corrosion. Floor pans are cancer free.

Powered by an L20b w/A87 head. Matched with a 5spd tranny. Thinking the trans is a 71b. When I separated the engine and trans found the clutch marked as a 72 240z only.


Posted pics on the 1st post but can't figure how to do it again.


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I'm usually not such a retard....just stepped it up a bit for this occasion. 

Trying to do this on my cell. Think I'll switch to my tablet......damn it.

All my shit is on this crappy cell phone....piece of shit.....

But I digress 


Awhile back had a 68' 1600 roadster take away a couple years of my life and mostly enjoyed it. Lots of great drives, shows, events and some really smart people.

Moved on and back to golf, and yes, I still suck at it.


Much like the roadster, big red was not on my radar. But I've personally committed my self to a great build. 

Build? That's a long-term kinda word. Crap, here we go again.


Thankfully I still have the experience and ability to take this truck on. 


With such an auspicious penetrer we will attempt to record our project here on rats in. Stupid spell chk



Motor/tranny out and split.


Looking for best driveability with reasonable power. 


The L20b/A87 is fresh with great compression. Cleaning and storage prep, throw a blanket over it and call it good for now. 

The motor came with a Weber 32/36. Recomendations?

Damn it.....still gotta pull the fly wheel and crank pulley. Add it to the list....


Trans #FS5W71B is need of help. 2nd gear synchro is hanging up. Going to be a full tear down and rebuild on this baby.

Which leads me to the following question.

Tranny guy recommendations?

Alright you pervs put it away...

Anyway, this trans is a mid-ratio setup. Would the close-ratio be better? Shooting for the sport's car feel. Oh, forgot, there was quite a collection of metal slivers and fuzz on the drain plug. Couldn't see any part #s so that's  ok. Right?

Haven't looked at the diff yet but thinkin some gearing may be in the future.


Enough for tonite. Think marathon.


One more thing.

I'm a former and present cheep ass

datsun owner.


Ok, one more thing.

Thanks for the info on uploading pics. I might just figure it out soon and get some gd f'ing pics posted.


Peace out.



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As you move to taller 4.11 or 3.889 differential gears from your present 4.375, you loose mechanical advantage and performance and acceleration slow down along with the engine RPMs. If not using the truck to carry a load you could run 3.889 or 3.70. My 710 weighs about the same as the 620 and a 4 speed 710 had 3.70 gears. It's a long long long wait revving through first with your foot to the floor, I'll say that.


A wide ratio transmission has a lower first gear with the most mechanical advantage. A close ratio has the least advantage but because 4th gear is always one to one, second and third have less RPM drop between shifts than a mid ratio and a lot less than a wide ratio.


I put a 4.11 differential in my 710 and eventually to a mid range and then a wide range 5 speed. It's subtle and you almost have to try both to get a feel for the difference for the bottom 3 gears. Forth is forth and the same in all 4 speed  transmissions. It's a good set up for a car with maximum acceleration in the lower gears and basically the same on the highway. The mid ratio was also very good. The close ratio would basically cancel out the 4.11 differential advantage in first but would probably be alright in a 4.375 truck.



The only L20B/A87 head combination from the factory was the '74 610. All '75-'77 used the U67 head on the L20Bs. In the '80s and late '70s it was cheaper to import and engine with low mileage and just swap the head on rather than rebuild it so anything is possible out there. Some A87s were closed chamber as well. No way would Nissan slip a mixture of open and closed chamber heads into production vehicles as they would fail the rigorous emission requirements. So this head may have been swapped during a rebuild or it's from a '74... makes no difference and after 35 years lots of stuff got swapped to keep an old Datsun on the road.

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A ka24de fell into our laps. It's out of a 1993 240sx na. No top harness or ecu. It's a Japan front sump with dip stick left and center. 

We were told it had 110k miles and that it should be overhauled.  It appears to have been mounted on the engine stand for some time. Pulled the valve cover found head and cams dry with quite a bit of varnish evident. Removed the worst looking spark plugs I've seen in awhile and drained about a cup or two of nasty oil. Oil filter was dry and the drain plug was clean. Looking down through the spark plug holes 1, 2 and 4 show pools of oil while 3 is wet but no pool. Timing chain looks good and tight. Crank and valve train work and makes some compression. 

Tried doing a compression check with a socket and ratchet, got a 30 to 35. Tried my half inch drive impact, no spin. The motor didn't come with a starter and my L20 starter won't fit.


While looking the engine over I found the vacuum hose between the egr and controller was heat damaged and for sure leaking.


I'm trying to determine if this engine does need an overhaul?

110k doesn't seem like a lot for these engines.


I would post pics but have yet to figured it out on my android.

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Probably had the shit driven out of it and was stripped for the mission parts. 110k miles shouldn't need work, maybe 110k miles since last cheap hone and ring job? Only if you got it for free .... take the head off and take a look, why the oil? broken pistons? measure bore diameter.


Walk away. Sometimes free to just too damn much. Get one you can drive and see how well it runs.

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Productive couple of days, the bed is off and securely mobile. Best thing, we caused zero removal damage. Took my time and disconnected everything yesterday.  The bed mount nuts, 8 each, were no problem for the impact gun. The bolts have lockplates welded on so the bolts don't spin.


Using the engine hoist and the leveler I rigged two ropes and used the corner bed hooks as lifting attachments. I built a standup dolly with a pallet the ka24 came home on and some casters. Attached a rug on my new dolly. Ready to dance.

I was thinking about doing the removal solo, but, the transfer from hoist to dolly and awkward size made me rethink this deal. Had a kid here my wife was paying to do some yard work. Nope, nice kid and all but passed on that. Decided I'd wait till the wife got home. Then thought if I had her and the kid I'd pull it off but the kid the kid was leaving. 

In the meantime there's that gas tank hanging off the bed. Was worried about the height restrictions with this stretchy ass rope. 

Went ahead and pulled the tank. Found the outboard mount bracket not attached, just kinda hanging there.

My wife was home so I'd just wait for one of the neighbors, the youngest daughter and her boyfriend. The daughter was 1st to arrive. 

Briefed the girls on how we were going to pull the bed, wife was ready and the daughter dubiose but willing. We lifted the bed slowly with the girls balancing each side. Only snag was the fuel vent was still connected. Once clear I rolled the truck fwd and the girls helped me settle it on the dolly. 



Under coat is flaking off in big chunks. Light surface corrosion with no rot. There is minor blistering along the attachment of the bed floor to the sides that has bled thru to exterior skin.


Rear frame 

Looks dirty as hell but except for the right ebrake cable being cut all is well.


I have pics so it did happen.

Still working on figuring out how to post pics..... ...



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I've lifted multiple cabs by putting a couple boards across from side window frame to side window frame, then pushing the hoist in through the window and lift the cab up from the middle. It's a bit wobbly but doable. There are also some really great attachments that guys have built for engine hoists specific to doing that job as well. Here's a link to one




No idea how much the 620 cab weighs, but I did this with 720 king cabs, so they weighed a little more than yours likely will.




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Thank you. Seeing the hoist inside had me doing the forehead slap.

What about attaching to hard points in the cabin...

1 hour ago, Lockleaf said:

I've lifted multiple cabs by putting a couple boards across from side window frame to side window frame, then pushing the hoist in through the window and lift the cab up from the middle. It's a bit wobbly but doable. There are also some really great attachments that guys have built for engine hoists specific to doing that job as well. Here's a link to one




No idea how much the 620 cab weighs, but I did this with 720 king cabs, so they weighed a little more than yours likely will.






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Just throwing it out there, as I know you limited on people but i had 3 people help my lift my cabin off (1 at the core support & 2 at each corner of the cab by the rear window) but that was completely gutted. No doors, hood, fenders, glass, etc, you get the point. Also didn’t have the motor or transmission as well so didn’t have to lift it as high. Hope that helps.

& don’t forget the steering column, very important when removing the cabin.

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16 hours ago, Snohomishdatsun guy said:

Thank you. Seeing the hoist inside had me doing the forehead slap.

What about attaching to hard points in the cabin...




I don't think there is anything wrong with building something that would attach to the cab.  I'm assuming you mean something that would bolt to the body mount points or other locations?  It would work fine, its just a great deal more work to build.  Unless you are really moving the cab a very very long distance over rough terrain and you were worried that it would fall off and get damaged, I don't think it would be worth it.  




We moved this truck cab sideways off the frame using wood inside the cab and rolled it on pavement and it was fine.  The stick at the front is to keep it balanced while it's just sitting there.  However, my way does still take two guys.  One to pull and one to balance.  Building a nicer rig like the one from my last post would allow you to do it solo.


So in conclusion, yes, you could make something bolt to the cab and be super secure.  There is nothing wrong with this at all, except it might not be totally necessary.  You just have to decide that the juice is worth the squeeze.

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Made it over to see the 1970 510 wagon. Over all solid car. Numbers matching even. Got it for a lot less than his asking price. I honestly think it won't take much to make it a runner.


He also has a 610 wagon that's not so nice. Whole bunch of useable parts tho. Block and tranny is still there and I think matching numbers as well. Cheap! I may grab the block, trans, driveshaft and diff.


Got pics but still not able to post.


Will start a new thread on the 510 soon.


Damn datsuns they've sucked me in again.

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You are on the correct datsun path right now.  I too started with 720s and then got myself a 510 wagon.  Which 510 wagon has a 1982 720 wiring harness, z22, and 5 speed 😄.  I even have a set of 720 AC parts laying around I want to shove in to it.

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