My 77 620 K/C 4x4 project.

[RacnJsn95]

I decided I didn't want to invest a lot of money into the 510 I had because it was a 4 door. I came across this 77 620 4x4 on a datsun forum a frequent, and stuck up a deal with the guy to trade him my 510 (paid $400 for it), and a $200 bucks for the truck. He towed it to me from Idaho, and took my 510 away. The bad thing about the truck? The engine had a rod knock, and must some broken rings or something, because it literally puts out a big ass smoke cloud when it ran...

 

 

 

So I built a new L20b for it. Used +.030 L18 pistons (smaller dish than the stock L20b pistons), and a closed chamber head. So in theory that should up the stock compression of 8.5:1, into the 9s. Everything is new except the crank, rods, and cam & rockers. I'll eventually replace the cam and rockers with something a little more wild little later on down the road. I bought dry film lubrication coated bearings for the bottom end, and a high pressure oil pump to help try to avoid more oil problems.

 

 

 

Got a "no smog" intake, and exhaust manifold to get rid of all that emissions bull shit, but ran into a problem with the Y-pipe, because I didn't have one, no one I knew had one, and there wasn't a single datsun in a junkyard from the era I needed in the rogue valley, so I had to make my own. So I took the flange gasket to the local water jet guy, and had him cut me one out of 3/8" steel. Bought some exhaust tube from the exhaust guy down the street, and had him bend them. The only thing that sucked was that I only had a hacksaw to cut the pipe with! So the cuts didn't come out that great and the gap was pretty large where the pipes came together, so I had to make 3 passes with the tig welder to close everything up...

 

 

Here is the most recent picture I have of it...

 

 

The engine seems to run pretty good, I've got about 10 miles on it. The carb that was supposed to have been rebuilt needs some help though, and I'm gonna have to have the driveline rebuilt with new U-joints, and a new front yolk. My truck has a Dana 30 in it, and a D20 transfer case, along with classic Jeep hubs.

 

I've always wanted a 4x4 620 king cab, but I've only been able to find std cabs, and half of them were a poorly done backyard conversion that looked like it could fall apart at any moment. So I've been slowly keeping my eyes out for about 3 years now, for a good clean, 620 King Cab that's been converted right, and not scabbed together. Had to be a king cab because I'm pretty tall, and my back hurts if I can't stretch my legs out far enough, like in a std cab truck.

[Icehouse]

I know I've said it before but I will say it again... I LOVE IT!!! you and Mike should put your extra parts together and build me on :D

[datzenmike]

Ice is right, wow. Got to get some stuff done this w/end to mine and get it closer to being on the road.

 

Jeff, I have a spare key from a '78 parts truck... you could plant it... and grow your own!

[RacnJsn95]

Thanks for the compliments guys. I'm gonna go out to the shop and see if I have any aluminum round stock left, and I think I might machine up a set of shifter bushings. The shifter in it is so sloppy it makes it damn near impossible to drive!

[hang_510]

depending on the tranny, i can set you up with a guy who makes brass sets for ~$24. i got NOS nylon myself.

[RacnJsn95]

depending on the tranny, i can set you up with a guy who makes brass sets for ~$24. i got NOS nylon myself.

 

You can buy the "HELP!" brass bushings for like $5 bucks...

[]2eDeYe]

Man that's a sweet KC.

 

The t-case is a Dana 20 (D20). Simple stout cases.

[RacnJsn95]

Ah, a D20, eh? I must have misheard my cousin. He's a Jeep fanatic, and I had him look it over and tell me what everything was. He's got a rad 42 Ford Jeep. (You know, the ones Ford made for the war, and its got Ford stamped into the back of the tub?).

 

Anyway, Today was good, but sad at the same time... I went down to the parts store and bought the "HELP!" chrysler door bushing kit #38377 (They make great shifter bushings!), and only $5.99.

 

Well, my old shifter was so worn out (The little ball at the end), that the little plastic cup thing that goes on the end fell off and wouldn't stay on. Luckily I had another shifter that was in good shape. So I put the bushings in the shifter, spent about 2 minutes with the round file to make the pin go in... Put the shifter in and it's about 100x better than it was, the only slop now is in the transmission itself.

 

In fact, it was so bad before I thought it was a 5 speed. It's so great now I discovered its only a 4 speed today! CRAP! Had I known I would have put one of the 5 speeds I have in while the engine was out! But it's just gonna have to stay a 4 speed for a while.

[makya]

That's the cleanest 620 4x I've seen in a loooong time.

[RacnJsn95]

Well here's my latest update. Truck seems to be running good now, shifting good. I did take the driveline to the driveline shop for new U-joints. I knew it was bad, I'm hoping it can just get me by for a while. The splines in the slip yolk thing have a lot of slop in them. It would be $160 just for the parts to fix that, and then labor, so probably in the 225-250 range to fix that, but for 280-300 I can get a whole new driveline made. I'll save up and go that route... I just had time replace the u-joints for a bandaid fix, so I'll be able to drive it a little bit, and for hunting season. It was $36 for the R&R of the U-joints, not bad, worth not having to do it myself.

 

Came home and put the driveline back in. The rear end has a super bad clunk. With the trans and transfer case in neutral, rear wheels on the ground, There is about 3/4" of play in it. Sounds pretty bad. And the 31x10.50s dont rub in the front when you turn. I'll have to have the springs re-arched to get another couple inches of lift to clear them :(

 

The zip tie throttle cable holder isn't really working for me, the cable isn't stable enough for me to get a good feel of the accelerator, and makes it hard to take off from a stop.

 

I really wanted to drive it to work tomorrow, but I can't decide now. Just driving it around in the yard was pretty sketchy, and I only went about 50 feet, so I could take this picture...

 

 

:( Wish I could have bought that SD25 :(

 

*EDIT* Hey guys... If you look at the front of my hood, where it meets the grille... Is there supposed to be a trim piece there or something? It looks really out of place. Man! that would be a sweet picture if that damn canopy wasn't on there!

[]2eDeYe]

Yep, there's a trim piece that matches the grille line...

 

Nice shot ;)

[datzenmike]

Most of the hoods I've seen are missing that piece or you break off the tiny bolts removing it. It's not that noticable, just paint it silver. lol

 

Kick-ass picture!

[Icehouse]

Jeff, I have a spare key from a '78 parts truck... you could plant it... and grow your own!

 

 

Haha I will have to wait until next spring. I want it to grow as big as your truck, I figure it will take a lot of sun :)

[RacnJsn95]

Well I drove it to work today... The trip there, and at lunch was pretty sketchy! I filled up the tank at lunch time though, and the drive home wasn't bad. Doesn't really have any "oomph" at all. Takes a long time to get up to the speed limit with normal driving. I think its too tall geared. at ~50 mph it only sounds like its turning about 2000-2300 rpms. I think I need some lower gears or something. Dad wants me to put smaller tires on it, but I think that would be dumb.

 

Overall I'm pleased with it... Just doesn't have to "oomph" I was expecting out of it. I knew it wasn't going to be fast or anything, but I was hoping for a little more "oomph" than it has.

 

Wish I could have bought that SD25 :(

[datzenmike]

My KC weighs 3,600 with me aboard. With 31s and 4.11 gears it's terrible on anything but downhill and on the level. I had 3.375 but the rear blew and all I had laying around was the 4.11s. Now I'm putting a Z24 for more torque.

[RacnJsn95]

Not sure what it weighs yet... Didn't want to chance stopping at the scales with no plates on the truck yet. I'm sure it's not light though, that's probably part of the problem. What are the lowest gears I can possibly find?

[Icehouse]

Find out what the rpms are on the freeway, I think lowering the gears would have a huge improvement. I had a 720 with 33's and the napz24 and it wasn't to bad, for its size anyways :D

[makya]

My standard cab 4x was about 3400 with 31's on it. But it's much lighter now, even w/35's:D

 

It's geared to 4.88 stock.

[lynchfourtwenty]

the wrong gearing + huge tires = slllloooooowwwwwww

[lynchfourtwenty]

and wow.. with the engine you built up it should run like a champ..

[datzenmike]

Not sure what it weighs yet... Didn't want to chance stopping at the scales with no plates on the truck yet. I'm sure it's not light though, that's probably part of the problem. What are the lowest gears I can possibly find?

 

 

Yours should have come with 4.375s already in it for that year, I think. You'd have to check, but some of the earliest 620, or 521s had 4.88s?

 

A garbage dump or a gravel pit are good places to weigh your truck too.

 

If the L20B is tired, it should be fixed first before changing to a lower rear gear.

 

Did I mention that the truck looks great?

[RacnJsn95]

and wow.. with the engine you built up it should run like a champ..

 

I think the weight, and gearing is the issue. The engine seems to run fine, and definitely isn't tired. A stock 72 620 weighs a little less than 2300 lbs, tack on a couple hundred pounds for the K/C. I bet my truck is between 3300 -3500 pounds. In theory, That's an extra thousand pounds on that poor little motor. That's a LOT!

 

I'm not sure if I did this right, but I tried to figure out how the 31" tires affect the 4.375 gears. IF I did it right, I'm really only driving around on a 3.21x gear ratio! That's not exactly optimal. I also need to find some lighter wheels, the ones that are on there are weigh ton, and when you can loose pounds of rotating mass, it helps a lot!

 

Did all 520, 521, and 620s have the H190 rear end? My cousin has what I think is a 66 or 67 if I remember correctly, but it's got the 1300cc ohv motor (A13?), with a 4 speed. What gears would that have?

[datzenmike]

Found out that the 620 with the J15 automatics and the J13 standards had a 4.625 axle. The J15 standard had 4.875s. Most others with the L series had 4.375s.

 

The early 620s used an aluminum housing for the rear gears, eventually switching to heavier steel.

 

I think the 33s I have give a final ratio somewhere around 3.70- 3.90 with the 4.11 rear. The switch to 4.11s was sort of by accident. I blew the 4.375s and 'thought' I had another set. It was from an '82 (Z 22 auto) so I should have known better, but was in a bind. Checked the pinion gear stamp just as I was installing them, oh well. Even with the 4.375s it was a slouch. Anyway, if I have a 700 lb load of firewood on I just use low in the transfer case if off road in a ditch. It's fine, but slow, if on pavement.

[RacnJsn95]

So its a J13, manual... I imagine it would bepretty much impossible to find a set of 4.625s for my dana 30 front end, that's a pretty odd ball gear.

 

Where the axle tubes on the early 620s aluminum also? I wonder how much of a weight difference there is from the aluminum to steel rear housings.

[datzenmike]

Datsunaholic mentioned it once a long time ago. The tubes weren't Al, just the housing. I seem to remember about 30 lbs. weigh difference, but don't quote me on that.

 

You never know about the Dana, they been around a long time. A Jeep off road club might know. As long as it's close it should be OK. As long as you are on a soft surface any difference in gears would just slip the tires. I have a 'Yoda 4.10 front and a 4.11 rear... the difference would work out to 1/100th of a tire diameter.

 

I looked it up and got: (there may be more)

Dana part#

706930-6X Rev. Rotation 4.56 41-9 $252.22