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1979 Datsun 620 Motorhome, upgrade & restore.


Deleteme

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Hey there, I just got this datsun and I'm looking to see what you guys might suggest for mechanical updates, aswell as the home on its back if you happen to have one.

 

I do have a particular question about the stickshift transmission reassembly, but first, a short story.

 

It's an L20b engine, with a 4 speed transmission, I purchased it from a guy who said it was having issues with the clutch: none of the gears would engage.

 

http://community.ratsun.net/topic/65335-transmission-not-engaging/?do=findComment&comment=1205150

 

Ofcourse I found this post after I had it towed.

As it turns out, the the rod coming out of the clutch slave cylinder, which actuates the clutch fork thanglejag, was pushed out half a pinkies length or so; It appeared to function correctly in all respects except for that. When crawled under and gave the bleeder screw a twist, not much fluid came out, even though the master cylinder indicated it was at minimum. The rod promptly slid back in its cylinder, along with the the fork which now allows for full engagement of all gears, without syncro grind. 

 

So strange this would happen after sitting, what do you make of that? It looks like there used to be a gasket or shim in the engine bay where the master cylinder bolts to the wall but I can't be sure.

 

After my initial inspection, of the slave cylinder which seemed to be functioning correctly (the mohome was parked in a marshy area and I didn't want to lay in the water for too long), I disassembled the stickshift to check for linkage issues that might stop the transmission from shifting gears, as it turns out, these datsuns have internal linkage stuff, so there wasn't much to see except for 1 bar connected to the stick, and after finding no fault and losing one sirclip I reassembled it.

 

Well, almost.

 

See, theres this one large bolt on the side next to the shifter it contains two springs and a third piece with a beveled line across it. Is it supposed to be so effing hard to compress and reinstall? I believe it takes up shift slop? It's in the glove box at the moment.

 

Also, can you tell me anything about the alternator? I was readjusting the the tension and the bottom bolt seemed to keep turning so I smacked the alternator taught and stopped turning it out of fear.

 

You guys where very helpfull in that other post by the way, thanks for that.

 

I'll add footage later :)

 

Sky

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The model you have is likely a Cab Chassis option. If converted by a company they don't want to buy a truck with a box on it they are not going to use. So it comes with just the cab. They only came with a 4 speed, the five speed would be too stressed to use it on a motorhome.

 

Sounds like the clutch slave line just got some air in it. Possibly the fluid got low enough to pump some air in and the PO just topped it up but didn't bleed it.

 

The bolt with the springs and the beveled piece is there to make the shifter naturally seek the 3 to 4 gate. When you shift out of 2nd the shifter naturally tries to move to the right and avoid shifting straight ahead back into first. The springs pushes the part with the ridge in it into a groove aligned with the 3-4 shift gate. Your hand can easily overcome this. Put it back together.

 

 

Alternator...

 

If you mean the bottom bolt that goes through the slot in the adjusting strap, it may be stripped. Easily done on an alternator's soft aluminum. If so, drill it out and use a longer bolt with a nut on the end. 

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Thanks for the welcome; Yeah mike my hand can overcome it, its just in an awkward spot, I'd like to make sure its normal to have resistance, also can you tell me if the beveled piece needs to be rotated so that the line mates to something inside?

 

 

Yes, you can look inside the hole and see a horizontal groove in the striking rod. When the shifter is left in the neutral gate is should shift over to the 3/4 side by itself.  If you pull over to the reverse gate and release it will return to the left, or should.

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Alright it was real easy threading that piece in from underneath now that its on pavement. Got the alternator off, thinking of taking a look inside as it has a bit of a squeak and is 40 years old. I'll have to see what upgrades are available. Got some new tranny fluid, hopefully the bolt comes out ok. Planning to redo the interior aswell as paint the exterior. Wishing I had chrome trim around the headlights instead of black :(

 

Thanks for the information mike....looks like its seeking the center so thats a good thing.

 

Thanks for the welcome redeye,goodluck finding one of these lol.

 

https://photos.app.goo.gl/QlSdYZSJ6sqVX3na2

https://photos.app.goo.gl/0PhpypahI8HOn4UN2

https://photos.app.goo.gl/56ZBW0yNXwXyavUG3

 

https://photos.app.goo.gl/8HVjsRV5yYWZfzFD3

https://photos.app.goo.gl/8xQLJDxNBS8f2TwS2

https://photos.app.goo.gl/F3cOuPRiTGs5Hh5m2

https://photos.app.goo.gl/0byhUEcxZ0OwLOei1

https://photos.app.goo.gl/6SLchGB5hYMuP14T2

https://photos.app.goo.gl/fByzY3XmWQ6OmjqJ2

 

Bah...didnt show up, ill make an album later I guess? Tedius but theres some picttures for yas

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It appears to have 720 rims on it, is it a dually with dually adapters?

From the front and side view I am thinking it might not be a dually, but it is hard to tell so I am asking.

I think you will find it to be under powered, but you have choices in that respect, I believe a hybrid LZ23 would make it enjoyable to drive, my work truck has an LZ23 and I haul weight all the time without issues, when I had an L20b with a super head it didn't have near the torque, and torque is where it is at with a mobile home.

Also you can bolt on late 720 vented rotor disc brakes which are an improvement to say the least, one of the best upgrades I made to my work truck at that time.

 

Stupid Google images will not let me post your photos, I would suggest using Postimage instead.

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No its not a dually but im keeping my eyes open for some, as for the hybrid lz23 idea... that'd mean plopping in half of another motor and slappin the l20b head ontop right? I did grab up a head gasket kit for later but I don't think I wanna do all that and plus I'd lose gas mileage with what I'm guessing is gonna be increased bore size? I do like the gas savings that comes with this little dar-v, and that's what I'm aiming for on this build.

I haven checked but I'm assuming its disc in front, drum in back...and your saying I can get bolt on upgrades for...the back? ...sweet.

 

Ill make sure I'm using GL-4, I wonder if I should change the differential oil aswell.

 

It doesnt look like air conditioning was an included option on this datsun... not that I want it.

Can you guys tell me what is supposed to be in the dashboard where theres a D?

heres a pic

 https://photos.app.goo.gl/b3jwmTYauSCIngWg1

https://photos.app.goo.gl/eyCdI9CvsCAKKCHG2

To the left of bowser the beast dog 

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That truck came with non-vented rotor front disc brakes, they work alright, but the 1985+ 720 had vented rotor disc brakes, they are way better and they bolt right in to your truck, you just buy everything between the ball joints and bolt it in including the brake hose.

As for the LZ23, I get better mileage in the work truck with it than I ever got with the L20b, I was always floored with the L20b, I am hardly ever floored with the LZ23 even hauling the trailer, I once got 23mpg in the work truck(empty going 70mph+) and it weighed 3400lbs(empty) back then, it now weighs even more because it has a dump bed.

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Hmmm.... Ill have to see about rear disc  brake conversion too.

The current shift stick is a little too big, gets in the way of getting to and from the back of the rv, the steering wheel is in the way aswell. I wonder how tough turning a smaller wheel would be without power steering - have any of you guys done this?

Wondering what junkyard shift sticks are interchangeable with this transmission. 

I suppose I could cut the stick and re-thread it.

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I personally will never have rear disc brakes, the rear drum brakes work fine and I haul a trailer around with a lot of pressure washing equipment in it, it also has electric drum brakes, rear disc brakes give you bragging rights but I don't believe they work better than rear drum brakes.

It is not easy to turn manual steering when your not moving, the lighter the vehicle the easier it is to turn, but once moving steering should not be an issue, the smaller the steering wheel the harder it is to turn, find a bucket seat that swivels if you have the room, that is what I would do.

All the really short shift levers are custom, but they made several different sizes and shapes, maybe someone on here has a short shift lever they don't like.

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Fronts do all the work when braking, there's no advantage switching the rears to disc, certainly not before upgrading the fronts.

 

I made a power steering for my 620 but don't advise it. It was a lot of work and customizing. Worked well though. If I did it again I would get one of the electric power steering units.

 

Shifter is too tall? You can bend it closer to your right knee. If shortening it, make damn sure you can reach all gears without leaning from a comfortable sitting position. You should be able to lift your hand off the wheel and set it down on the shifter, even in third, without moving your shoulder off the seat back.  Gets damn tiresome having to lean forward to grope for the shifter. I would shorten (if at all) by taking a section out and then have it welded together. Also shortening reduces the mechanical advantage. Shifting will require slightly more effort.

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So I took the ol' rat for a romp, now I've got some curious deets.

For starters - it fires up on a single crank, pretty sweet (pun intended).

I have a shiny new carburetor, I'll be installing it.

There's a flat spot when you slowly press on the accelerater peddle where it's getting either to rich or too lean of a mixture, but pressing the peddle past that and it's just fine.
So it bogs down at that point and I figure it's happening between where the main jet takes over from the pilot jet.
I no nothing about this carburetor.

I went on the highway, cruises ok but on an incline I slowed down to about 60, givin it more gas just slowed it down more!
Hauls pretty good in third but fourth seems sluggish.

The transmission: Shifting quirks... Finding first sometimes the stick doesn't, at a red light the stick won't push into gear, if I depress the clutch peddle and try again it works.
Now when stopped, shifting into reverse makes a grind noise but I can press harder and it goes, I pressed the clutch in for about 30 seconds, then tried to shift into reverse but it still grinded. I wonder how long that main shaft spins for when disconnected?
Does the reverse gear have a synchro? I will pull off the clutch slave cylinder, inspect, hone n reinstall.
Also, shifting into first clicks up once into a distinct position, and then clicks forward a SECOND time? second and fourth aren't doing this and it's very strange.

 

The brakes...slow to stop.
Not cool.
E-brake works though.

Great on gas, beach was nice.

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Your clutch might not be adjusted correctly and that is causing it to drag, or something in that circuit could be wore out or going bad, reverse has no syncro.

When you let out the clutch to move does it start grabbing even with just a little lift of your foot or do you have to let up a long ways before it starts to move, you should only have a small amount of play in the clutch pedal when it is not being pressed down.

 

As for the brakes I mentioned this in my first post in this thread along with the truck being under powered, you can upgrade the brakes, it is a bolt on if you can find a 1985/86 Nissan 720 truck in a wrecking yard with everything still there that is in good shape, it is a great upgrade and you will be very happy with it.

Do you have power brakes?

 

The engine is a little more difficult to deal with, your shiny new carb might help a little, but in the end you will need an exotic intake system to really get more power out of that engine, and you do not want a cam, a cam might help you a little(very little) on the hiway, but the better it acts on the hiway, the harder it will be to get it going from a stop, the more horse power cam one uses the less torque you have to get it moving.

There is no substitute for displacement, the larger the engine the more power you will have, I mentioned the LZ23, that is what I would do if I were you, but I would fix the mobile home up first and use it for a little while before building an LZ23, you can use it while collecting the parts needed to build an LZ23, if I can haul loads like this in the photos below and get it moving and stop it, you will be thrilled with what I have done in your rig, but I have dual SUs for carbs, I hate downdrafts, I find them hard to dial in even if it is a brand new Weber, while I can dial in SUs without any problems as long as they are good also.

To build an LZ23 you will need a Z22 block out of a 1981/82 Datsun 720, I would find a decent earlier L block head(A87/U67/219), find an early Datsun 521 L block exhaust manifold with head pipe(non smog), and I would find a decent set of Dual SUs, but an A46 intake manifold with a Weber will work, a good stock carb will also work.

You can use the head and intake/exhaust you have on the Z22 block also as it is already there, that will be a much easier route to go, but not sure if it will have as dramatic of a result as doing what I mentioned above.

DSCN0393.jpg

Here is another load.

mg_td_001.jpg

This load just last fall.

DSCN7200.jpg

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Holy shit. That's alot of wood.

 

And the brakes I had stopped it, they were 1990 Nissan Hardbody V6 dual piston vented rotor brakes, but the 1985/86 Nissan 720 brakes will work just as well for your situation, as your not hauling massive amounts of weight like I hauled all the time way back when, well I still do I just don't drive a 100 miles to get it off my friends property anymore, I get it locally now from my customers that cut down trees on their property, or sometimes I pay for it(usually cheap).

The 85/86 brakes I am referring to will not bolt onto your spindle assembly, you need everything between the ball joints(I get the ball joints also) and the brake line hose, it is a bolt in upgrade in your situation as you already have ball joint control arms.

I have a dually axle under that truck, but the H190 is rated for more weight than my dually axle, I have hauled a lot of weight on my single wheel H190 axle also(like what you have), but I converted over to the dually axle around 15 years ago, I have wore out a few of them also(the gears and carrier, not the bearings), you can make that mobile home a pleasure to drive with a little bit of time/effort/money, it will never go up a steep grade at 70mph in 5th gear, but you will not drop below 50mph except on the very steep grades, I pretty well drive the speed limit on the freeways carrying all that wood, but I do leave space between me and the vehicle ahead of me.

I expect the way your talking that you only have a 4 speed, you could convert to a 5 speed, but likely the reason they came with 4 speeds is because pushing around weight in 5th is hard on the transmission, but I use 5th all the time hauling my trailer around, you can install a 5 speed, but every time you came to any hill you would/should down shift into 4th gear, as the transmission will last longer, that is likely why they came with 4 speeds.

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Alright, I'll be saving this brake, axel, transmission and engine information for future reference, we'll see if I can collect them in time.

 

The clutch engages not too far out, but I suspect it must be the slave cylinder.

Shifted all gears just fine after I bled it, hasn't been that long, so must be the culprit.

 

The brake system has a dual reservoir master cylinder, it is hydrolic but I didn't see see any vacuum lines to make it power assisted. I did notice a small rpm drop when I press the brakes, so I'll have to follow the...lines.

 

And yes, It's a four speed.

I figure high rpm in third rather than too low in fourth, is best for the gears right now.

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You have power brakes, as I believe I can see a little bit of your booster and the line that goes to your intake in the 7th photo.

The L20b just don't have enough power for the 620 mobile home in my opinion, but nothing I can afford to own has enough power so my opinion is tainted.

The trouble with Mobile Homes is they tend to sit a lot, and the older they are the longer they have sat, master brake cylinders/clutch cylinders and slave cylinders tend to rust when they sit for long periods of time, especially the slaves, if the slave is bad and leaking it will tend to leave a puddle on the ground under it.

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Yeah, the datsun seems to be coming back to life with usage.

 

I'm having a problem with the fuel pump, it's next to the fuel filter.

 

When I turn the key to 'On', with or without starting, the fuel pump starts clicking. At first I thought it was normal, like it's supposed to run at all times. Now it's making a louder more violent noise and the pickup won't idle!

 

Just popped in some new iridium plugs, much smoother now, so that's good.

 

Any advice? Is it normal to pump 24/7?

Is there a relay?

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The 620 with an L20b didn't come with an electric fuel pump, if you have one it was added on at some point, it making noise isn't something that I can diagnose, you likely could go back to the mechanical fuel pump if you wanted to, when the electric pump was introduced in 1983 I believe it was back right next to the fuel tank and they did have a relay that shut the fuel pump off after a certain amount of time of the engine not running or if the truck were upside down. 

 

You should actually be using normal NGK plugs, these are classic engines not modern engines, you likely would gotten the same result with the normal new NGK plugs that are recommended.

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I am using NGK plugs, they were recommended on the Canadian tire website. I know copper is best but I got iridium for longevity.

 

I crawled under and pulled off the pump, the fuel filter was clean and mostly empty.

 

A couple knocks on the gas tank showed it was empty!

 

The gas gauge is at the first line after the E, is this line not the quarter tank mark?

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The '79 620 had electric fuel pumps if they had air conditioning. The York pump is bolted on where the mechanical pump would have been.

 

The stock pump also has a bottom the twists off to get at the internal fuel filter.

 

Does the gauge drop to empty when the key is off? If yes then the gauge is not stuck

 

Does it go up if you fill it? Float may be rusted in place or bent down or tank has a large dent in the bottom..

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