New 720 4x4

[HRH]

Well, found a peach on craigslist the other day. 217k $500 4x4. 1981, Datsun, not Nissan! Z22 motor also, which is nice for the hotrod bug, though I'll probably keep it low compression for cheap winter driving and because I don't feel like building another motor at the moment. Runs like shit, but has potential to run just fine. No rod knock, just spark/fuel issues. Limped it home, going to attack ignition first tomorrow, then carb/fuel issues.

 

A few rust holes in typical 720 fashion, but nothing a few plates and some welding can't fix. Flintstone holes are less than the size of a fist. The downside is I'll probably be selling the 620 if I get the 720 running well. Don't need both and I can offset some 510 rally car parts, soo we'll see. In fact, I may try an partial trade it for a subi LSD a buddy is holding so I can buy. He wants a bit for it though.

 

EDIT: Ooo! Note the hot-poop version! Tachometer AND power steering. Cadillac of Datsuns for 1981. :)

 

Anyway, here are some pics:

 

 

 

 

 

[xtrmemtnmn]

Nice find, I would take it, but you will regret getting rid of the 620. Don't do it

Edited October 21, 2008 by xtrmemtnmn

[irsa76]

Cool. The dash looks like it's not cracked as well.

I need another 720.

[HRH]

Well, should have checked the compression before I bought it. Thought it was going to be an easy fix, threw some new wires and plugs on, tweaked with the carb and replaced some oozing fuel hose. Still ran like crap, but a little better.

 

Next step was the thing I should have done in the first place: Compression test. 4 and 3 didn't register on the gauge. Thought it was malfunctioning until I hit 2. That was around 160. So yeah, rebuild or new motor. Found a few options, we'll see what we have. I've gotten pretty lucky with $500 finds, so stands to reason this would happen sooner or later. Good thing I have a lot of tools!:D

[datzenmike]

Quickly check the valve clearances. Likely it a blown gasket when you have adjacent low cylinders. Take the exhaust off, leave the intake and carb, pop the head and throw a $30 HG on her and good for another 100K.

 

All the early '80s up here are long gone (or look like shit). Nice example of what they can look like!

[HRH]

Yeah, I actually went by my buddy Todd's house (and fellow Datsun nut) and he mentioned it could have jumped cam timing, which I'll yank off the valve cover tomorrow and verify teeth and check for dead hydraulic valves. It would be nice if it was something that simple, and it does seem odd that there is 0 on both 3 and 4, yet it still runs and no smoke or other real issues.

[datzenmike]

No lifters, the rocker arm rides right on the cam lobe.

 

For the Z motor, turn the engine until the very front lobe is pointing down. Adjust the valve lash on 1st rocker, the 4th, 6th and 7th.

 

Turn the engine until the first lobe is pointing up and adjust the 2nd rocker, the 3dr, 5th and 8th.

 

Set the intake and exhaust lash clearance to 0.012" while motor is hot. Done.

[HRH]

Huh, I thought it hydraulic like the KA. Cool, I will check that tomorrow, though I'll have to run it about .010 since I'm going to be checking it cold. I suppose that's the other thing, the lock nut could have come loose and let the rocker arm up.

[datzenmike]

Loose rocker and the valve would open less rather than staying slightly open... and the noise would be LOUD!!

 

I'm not expecting the valves to be too tight, it's just the sensible thing to check and it doesn't cost anything.

[Cuts metal like mad]

3 & 4? I have seen a dozen 720s with the Z motors with the exact same problem... I hope, for you, its just the head gasket... could be gasket and block, or just block, could also be gasket and head. Good luck!

[HRH]

Hmm, seems funny it would be that since it's not blowing water, but makes sense. One down one up, leaking in between. That'll be the next thing if I don't find anything under the valve cover. Good thing is I have two spare z22 head gaskets from a previous race motor.

[HRH]

Well, I'll find it after I yank the motor. Bought a z24 from an interesting fellow, but popped off the valve cover and looked down a spark plug hole before I bought it. Supposed to be rebuilt head and 90k on the block, and if it is, I got a great deal for $140. On the other hand this guy was beyond redneck out in the toolies. Seemed alright, but damn...not the kind of guy I usually buy stuff from. Going to see if I can swap the motor tonight with a few gasket replacements.

 

That way I can keep the Z22 block it has currently to make another race motor.

[datzenmike]

Look like this:

 

http://i138.photobucket.com/albums/q251/datzenmike/deliverance.jpg[/img]"]

 

If he was bare foot did you count his toes?

[HRH]

No, but I counted his missing teeth. :D

[HRH]

Good call on the head gasket. Missing a huge chunk in between 3 and 4. Just finished stripping down the Z22 to the block. Hardly any cylinder ridge, pistons look good. Should be perfect for a future Z22/20B combo.

 

Here's some pictures from earlier:

 

 

 

 

I like making messes. :)

[HRH]

So apparently when someone posts a motor on CL and they look shady, they probably are. Knew I had a bad feeling about the Z24, and now it's confirmed.

 

While the head looked new like it was supposed to be, and the timing chain was new, not only was it incorrectly ramped, but the washer that fits over the dist. gear on the crank had been eaten up and beaten by the gear somehow. I had to cut the crank gear sprocket off partially to dislodge it and the ill fitting woodruff key.

 

And then when the head was finally off, #4 cylinder (the one I didn't look at) must have been full of water for the 4 to 5 years the motor was sitting, as it was completely rusted and the motor will not turn completely over due to the rust ring and sediment collection on top of #4. F***ing lovely. Will investigate whether or not I have to have the cylinders bored later. :mad:

[HRH]

Ah, and a new day comes with new possibilities. After sitting with marvel mystery oil in the cylinders/rings all night, I got a little more rotation out and was finally able to rotate the motor fully. Good news is I think I might be able to get away with bottle brushing out the rust, and just re-ringing and re-bearing it. Which would be nice since I'd rather not have a machine shop bill for new pistons and boring.

[HRH]

So the Z24 is a no go. Rebuilding the Z22 and going for assembly today. Bottlebrushed the cylinders, need to take off the ridge with a drum sander. Not much, just a little bit. Going for getting the motor together today and back in the truck? Is it doable? That's the only thing that sucks about cold weather and not having an insulated garage. Anyway, wish me luck!

 

 

 

 

[HRH]

So it's not a Z22. As I was cleaning yesterday, it's a Z20, but not a car Z20.

 

Oddness came when I went to install piston rings last night and they wallowed in the lands like drunken sailors. The car Z20 pistons I had left over fit the standard Z20 rings I had, but these Z20 truck pistons are like 20b rings, except the piston is decidedly Z. Think I'm going to throw the car pistons in if I can, but I worry about valve clearance. Fing weird.

[HRH]

So today it was either get the 4x4 going or don't make it in to work. See pictures of snowness in the general thread.

 

Anyway, now one more 720 is on the road with new bearings and used rings, and a cut exhaust pipe which needs to be welded. But the 4x4 works and that's what counts with 15 inches of new snow in the past 48 hours.

 

[tdaaj]

what ever works right? thing about datsun motors are they are very forgiving.

[Happy]

you get more done in a month or so than I get done in 5 years. of course, not only did we get a foot of snow, but 15 degrees below zero really puts the crimp in working in the unheated garage. I found that my Datsun's always blew a head gasket if you ran them at 15 or 20 below, so I wouldn't even dream of having one in the winter around here now. My 1985 4X4 almost got me froze to death one winter because of that. having to hang your head out the window while being towed with a chain down the highway, and you cannot defrost your window in that kind of cold is a thing for young, and dumb, man. At about 25 below, things break, like vinyl seats and whole interior panels that you didn't realize could break in half like that.

Edited December 21, 2008 by Happy

[ronnny]

My 81 has a 2.2 but it is a 2by not like your 4by. Your looks like it is missing a few options but still a very nice find. Wish i could find a deal like that on a 4by so that i could let go of my k10 and still have 4by4. Could of got a good deal on a mazda 4x4 but not sure i had bad luck on the 1 yota i bought. Good luck with it.

[HRH]

She looks pretty decent from 20 feet away, then you see they did a quick spray over the rust. :) That's the only bad part about this truck, lots of rust. But, I named her (Gracie). Seems to be reasonably solid, and since I've sunk so much into her already with bearings and seals and the new 20b clutch set I was saving for the race car, she'll probably be kept for a bit.

 

I haven't found Datsuns to blow head gaskets other than every 100-130k on the older motors. But if you do the timing chain like you're supposed to at 100k, you're likely to take the head off, in which case the head gasket issue goes away with recommended replacement intervals. Of course, it looked like the chain on this one had never been replaced.

 

I have a new Weber coming as I'm paranoid about the stock shit carb being too lean for the motor also. There is something wrong with the secondary so I'm trying to be pretty gentle with it. Primary works okay, though there is a carb-related intermittent idle issue. Seems to have fixed itself at the moment.