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Father/Son 77 Datsun 620 KC Build


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One thing to watch for, the gas tank is mounted to the underside of the box


The bolts holding the box to the frame were a major PITA to undo, start soaking them with penetrating oil now & often. The bolts have an offset washer-type thing as the head (no hex) and after 40 years of crap on them, they don't want to undo. I had to jam them which isn't easy to do as there is very little space there, and the washer head would simply bend & the bolt spin... No pic of those nasty little buggers.


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On 6/23/2020 at 7:27 AM, EDM620 said:

 The 620 tank is mounted to the underside of the box, the 720 & D21 tank is mounted to the frame. Pic attached is a 720 frame. 720 tank (& I assume the D21) is larger capacity as well.



The '78 and '79 620 tank is also bolted to the frame.




The long small hose connects to that Tee by the thermostat. That small hose goes down to the TVV thermal vacuum valve just below it on the thermostat housing. The other end of the metal tube from the TVV is beside the carburetor in the picture below. All you have to do us plug it in.


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great pics @EDM620, the current gas tank has a hole in it and seems like the last bit of gas came out during transfer to our house. Should make it a little easier to lift. Thanks for the advice on starting to soak those bolts now. I'm going to head out there in a few and start spraying them down. From others threads on here, they never go easy lol. 


@datzenmike, thanks for the direction. I don't think I'll be messing with what's in there now. Between the hole in the gas tank that we found on the last inspection, most of the hoses having dry rot and having no idea what condition the motor is in at this point, I think we are going to just pull it and disassemble on a stand and go from there. Even if we don't rebuild completely, it will be a great experience for my boy to take one apart. 


Ordered a few books on the L20b which should be getting here any day now. Might sell off this one and hunt for a KA swap. Still up in there air though. 

Edited by RustedRails
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I wish I had seen this warning about those nuts not wanting to unbolt themselves. I attempted to drop the tank on my 78 620 early this morning and even though I gave them a good soaking with wd40, i wished my pb blaster would not have malfunctioned and leaked from the cap, its my fault. I snapped two of the bolts, both on the inside front lip of the tank, and I am pretty sure this will take some time to figure out if I can just back them off from the underside with some locking plyers, or if I have to, drill them out and retap them. Well, cannot complain I am not learning anything during these crazy covid times. The tank is off and at the performance radiator where they are going to dunk. I found a second fuel filter behind the fuel door. Any ideas where to get one of those?


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3 hours ago, datzenmike said:


Yeah the '78 and up tank if different. That isn't another filter, it's a check valve to prevent gas escaping in the event of a roll over.

 Like Datzenmike said, that isn't a filter, it's a check valve, shown in this pic (of my 720 frame) in the yellow circle,  the filter would be located in the blue circle.

I had assumed the 620 tanks were all mounted the same until the actual model change to 720, but stand corrected.

That being said, if buying a replacement tank you may have the ability to swap in the larger capacity tank from the 720 like I did, nearly double the size. Placement of mounts obviously would be important. The new one in the pic has clearance for my King Cab which I needed.

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4 hours ago, charleybucket said:

Any ideas where to get one of those?

I had thought possibly RockAuto but I just checked and no listing for the check valve. Maybe Ebay or local Nissan store (shouldn't be expensive even from them).

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To be totally correct January '78 or half way through the '78 model year. Model years start around June of the previous year, why? who knows.


48 minutes ago, EDM620 said:

I had thought possibly RockAuto but I just checked and no listing for the check valve. Maybe Ebay or local Nissan store (shouldn't be expensive even from them).


Is it missing? Otherwise it doesn't wear out unless you roll your truck 5 times a week. The part number is 17330-U7400 about $40 if Nissan stocks them still. Used through '82 (ish) in the following... B210, 210, A10, S10, S110, 810, Maxima, and the 720. 

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So got a little time to work on a few things today after work.


Bed removal

Looked under at the bed and looks like there are only 4 bolts holding it down which I feel like is a score since hearing the nightmare stories about removing them. Back two by the bumper came out easy and looks like they were replaced at some point because the bolt had a hex head on it. Was able to use two wrenches to get em off.  The other two closer to the cab....they are original....and stuck. Hit em with some pb  blaster and let em sit while we jumped to the front end. 


Front end tear down

Front end went a little smoother. I had my son turn about 90% of the screw drivers/wrenches on this one. Between the caked up paint from a few different color changes and the grime/rusted parts...his patience was tested. Fortunately.....with a little encouragement and some helpful tips on moving to other bolts and angle of your wrench...he persisted and got quite a bit done for the time we worked on it. First lesson on "...if it was easy...everyone would do it" and "this is why people pay to have someone else do it...." haha. He thought that was funny and felt really proud when we closed up the garage for dinner. 


Now pics...nothing most haven't seen before but this is our progress 🙂


Grill off



Headlights and bumper out



Found a little surprise in the turn signal





Battery tray



Removed front end parts



Will hit work on the bed bolts tomorrow and see if we can't get that bed loose. Still need to work on the tank and get a few volunteers to lift it off. I was under there today and saw a few things that need to be disconnected. Thanks for the helpful comments everyone!

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There are 8 attachment points for the bed. The bolt heads have an eccentric washer welded onto them. When tightened the washer turns and jams so the nut can be tightened. Loosening is the reverse however the washer is very thin and will fold over allowing the bolt to just keep turning.

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One piece of advise for later in your build, is to mark your bolts once you've torqued them to spec, especially those on your suspension & brakes. Use a paint pen and mark the bolt/nut and where it aligns.


This serves 2 purposes: 1) since we all don't complete a build in one day, helps keep track of what you've completed; and 2) for the first while once it's on the road you can easily do a visual check to make sure that everything is still buttoned up solid. Avoids you being the guy on the side of the road with the front suspension that fell off.


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So the engine bay tear down continues! Got some time after work to get a few things done. We got most of wiring harness disconnected and labeled. The harness is a hot mess with all kinds of splices and repairs by the battery, to the alternator and starter etc. Will reassess when we pull the whole thing and get a feel of what's under all the electrical tape. 


Also pulled the valve cover just to see how it was looking and think I found out why it stopped working whenever it was that it last ran. 


Current state 












Should have a hoist soon. Getting close to pulling this sucker out. 

Edited by RustedRails
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It's very clean under the valve cover. The rocker is pretty common. If the valve lash is not adjusted correct, this happens. I see the tappet is still there so that makes it easy.

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So, got the tail lights and bumper removed. Also, got the last of the bed bolts off.....see the carnage below lol. I soaked em often and ended up having to jam another bolt in the cavity similar to what @EDM620 said and eventually snapped it off. 


Also started to poke away at some of the bondo on the bed. Won't get a good feel till I get a heat gun and scraper out. 


Got the engine hoist finally, now with the bed loose, (will be disconnecting the rest of the things tying it to the bed/gas tank) should be able to remove it, then engine pull is next. 


Tail lights and bumper off.






Behind the curtain




Edited by RustedRails
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