This truck belonged to my late father in law, Mac. He bought it shortly before giving me his beloved 1964 Ranchero. After Dad passed, and Mom needed to sell Dad's truck, I brought it back to my place to get it running right, clean it up, and sell it. I started documenting it here so I had a record of it for selling it and because it was the last vehicle that Dad worked on. His handiwork is everywhere on the truck, and I really missed having him around to bounce ideas off of as I was trying to get it running right. Ultimately, the truck ended up being sold to Trey, a son of some good friends of ours in "as-in" condition so he could repair it himself and get a first truck for a low price plus some "sweat equity". I helped him with getting it running right, the details are below. I'm keeping the page up since he'll no doubt be asking me questions as he continues to work on his first vehicle and goes through the learning process all self-taught mechanics go through.
It's most distinguishing feature when I got it (other than not running right) was the annoying back up alarm that played "it's a small world" that a previous owner (aka, before Dad) added to the truck. I clipped that wire before I took it off the trailer - actually, I was so annoyed by it that I yanked the wire apart with my bare hands. :-)
The pics above are the "after" pictures we took of the truck after Trey and I got it running and gave it a thorough wash and wax. It's pretty darned nice for a first ride. The AC even works. Trey is one lucky dude.
The truck is a 1985 Nissan "king cab" (Nissan's term, I'd be less generous) 2 wheel drive pickup with a 2.4L 4 cylinder Z24 engine, a 3-spd automatic transmission, 3.889:1 rear axle, power steering, AC, cruise control, tilt wheel, bucket seats with a console and a floor shifter, a roughly color-matched cap on the back, an AM/FM/tape radio that doesn't appear to work, and a CB radio that Dad added.
I couldn't find anything on the body to designate the model, which is weird. You almost always have a sticker or badge proudly proclaiming the model. The actual model is on the title as "72K" and some parts catalogs list is as "720" or "PL720". The factory service manual says the model is "720", but that's buried pretty deeply inside the text of the manual - it's not even on the cover or anywhere else obvious. I guess Nissan wasn't much into model names for their pickups at that point; I guess if you only make one truck model, there's not much confusion about which one you mean when you say "Nissan truck". It look like this is an internal engineering designation that Nissan updated every few years when they redesigned the truck, earlier models were numbered progressively as "220", "320", "520", "521", and "620"; later models were "D21". Wikipedia's Datsun Truck article is reasonably helpful here to explain the history and details.
The model designator is KNL720KV, if Dad's marking in the manual is correct. I tried to get this data from the data plate on the fender and confirm, but the data plate is missing, with just a suspiciously clean place left on the inner fender to say it was there up until fairly recently. For now, I'm going with Dad's notes. This decodes to:
Weight, tire size, and other related info on the data plate on the driver's door pillar, as well as the manufacture date of 4/85, clearly making this a mid-1985 model year truck. The last bits at the bottom right are the VIN - "JN6ND06S 0" and "FW 031982". That decodes to:
VIN. It's an upside down funky shot because of how I had to take the picture. See above.
Engine type and serial - "Z24" on left pad is the engine type and "470768" on right pad is the engine serial number, which matches the VIN and data plate on the door pillar (see below). This is looking down at the block between the center of the two exhaust manifold sections. A bit of wiping with a rag and the numbers were easy to see.
Spark plug data on valve cover decal. Note that the exhaust and intake side spark plugs are not the same, odd, but true.
Tune up data and vacuum hose routing on under-hood decals. Most of the vacuum hoses are gone off of this truck. It's been, um, "simplified". The tune up data confirms it's a 1985 model year truck.
I still need to get pictures and info from the transmission and rear axle stampings to confirm them, as well as the vehicle identification plate on the passenger's fender.
Getting it Running Right
When I got the truck from Mom, it was barely running. It ran enough to move around in the driveway and pull on to and off of the trailer, but that was about it. If you didn't give it gas it would stall, and it shook like a paint mixer at anything under 2000 RPM. Some cylinder were clearly not firing, but I was not yet sure why. Vacuum is choppy at idle, and it smoothes out to be pretty smooth as you bring the RPM up. Oil pressure seems fine, and it does not overheat. There were no excessively odd vapors out of the exhaust or internal death rattles from the engine. I did discover the exhaust manifold is cracked, so it will need to be replaced.
My initial guess was ignition issues, so I did a basic tune-up. I changed the plugs, cap and rotor, and bumped the idle speed up a bit. It ran a bit better, but it's was clearly not anywhere near right yet and definitely not good enough to drive anywhere. I then ran a compression test, and it was quite revealing. Expected compression is 130lb to 170lbs in each cylinder; here's what I found:
Those last two are not typos - the rear two cylinders had zero measurable compression. The head or block could be cracked, or the pistons could have holes in them, but since the motor was not making any death rattles that seemed to rule out major internal problems or damage, though it could still be a problem. There was no coolant in the oil, oil in the coolant, or compression leaking into the coolant, so a blown head gasket is possible, but it would have to be blown between the two cylinders. I would have expected some compression in that case, though it's possible since I had all four of the intake side plugs out of the engine when I ran the compression test. Some stuck valves were also possible causes, but we ruled that out by removing the valve cover and turning the engine over - all valves were operating freely and the top of the head was in good shape.
Next up was pulling the head to find out what we find and see if we need a simple head gasket, or a whole new engine. After lots of pulling parts, we got the head off, and found the problem. It has a blown head gasket and was driven with it enough to screw up both the block and the head between the #3 and #4 cylinders. So, basically, the engine was dead as-is, and needed a full rebuild or replacement. The pictures below show the gory details.
We found a used engine with about 150,000 miles on it for $400 and picked that up. It's a 1986 motor with a TBI setup on it, and the TBI setup will be useful for a possible later EFI conversion. The new motor was for a manual (needed to swap the flywheel for the flexplate from the original motor) and it didn't have AC (needed to bolt the compressor and bracket to the new engine). Nothing huge, just more little things to do. We saved the original motor for a possible rebuild later.
In case I needed a whole new engine - and eventually, I did - I looked up what interchanges. A simple straight-up engine replacement would be any Z24 2.4L engine from a gas (aka, not diesel) powered carbureted 1984 through 1986 Nissan 720 pickup - Hollander interchange #77024A should get you what you want from the salvage yard. The 1981 to 1983 720 pickups used a Z22 2.2L engines, Hollander #77022A. Note that 1984 was the first year these trucks were commonly known as a Nissan; 1983 and older were known as a Datsun. Most of the literature I can find documented them this way. I believe there were the same basic design with a shorter stroke and a lower deck height on the block. They likely physically interchange, but would be a downgrade, and so would be undesirable. Some 1985 and 1986 720 pickups, the 1987 to 1989 D21 "Hardbody" pickups, the 1987 to 1989 GC22 Van (rarely seen due to an en masse recall, apparently), and the 1987 Pathfinder all used a throttle body fuel injected version of the Z24 2.4L engine, Hollander #77024B. Since it's a TBI style system, there is some chance the intakes are the same for the carb'ed and fuel injected versions. The intake manifold should swap as a whole, if needed. So, the later motors are a possible swap candidate as well.
Some of the year transitions on the items above are not exact. It's not uncommon for "late year" production vehicles to already have transitioned to the following year vehicle's specifications, or in the case of the 720 to D21 changeover, to an entirely new model. This is kind of important when hunting down parts and the like, and should be kept in mind - always validate you have what you think you have to prevent surprises. The non-US car manufacturers didn't adhere to the same concept of a "model year" as the US manufacturers did, they tended to make running changes as needed, and when they ran out of enough parts to make vehicles one way, they changed over to whatever was next in line to be produced. This is rather helpful from a cost perspective, and makes sense when you consider how many different markets these vehicles got sent to, but it can be a hassle when cataloging important details and hunting down replacement parts. Those readers familiar with older air cooled VW's or Porsche's will be familiar with notations such as "up to serial #1234567" on parts interchange - the same basic concepts apply here, though the frame # transitions tend to be less clear (or perhaps less clearly documented) on the Asian manufactured vehicles, at least in my experience.
Here's the basic exterior pictures. It's in pretty good shape paint and body-wise, and the cap is in decent shape as well.
Here's the interior and dash; also in good shape. Check out the mini-gauges Dad added under the climate controls to keep tabs on the oil pressure and amperage. I'd prefer a volt gauge and an electric oil pressure gauge that didn't disable the factory idiot light, but Dad like the old-school amp and mechanical oil pressure gauge. I later found out that 4x4 models came with factory installed oil pressure and volt gauges in that space, and it looks like the wiring for them is in the main wiring harness. That could come in handy later on...
The mileage when I got the truck was 141,149. I have no reason to doubt it - the engine is original (see VIN and engine stamping info above) and seems appropriately greasy for it's age.
The obligatory engine pictures. Note the vacuum gauge Dad mounted in the engine compartment. It made tuning a bit easier since it was always there.
The #4 exhaust spark plug that I removed while doing a tune-up. Look very closely at the insulator around the center electrode - it's broken loose with no obvious cracks, and slides up and down. With the plug upside down (electrode up), it looks normal. With the plug right side up (electrode down), the insulator slides down until it touches the side electrode. Weird.
The engine before we started the teardown to find out what was wrong with it.
The battery terminal cracked in two when we tried to remove the negative battery cable. A bad omen...
Some in-process shots of the engine teardown to get the head off and find out what was wrong inside the rear cylinders.
The camshaft sprocket and timing chain when we hoped to be able to get it back on. It turned out that the chain came off the crank sprocket, so we gave up on the whole block of wood approach recommended by Hayes and just yanked the head...
The problem - the head gasket was blown out and completely gone between the rear two cylinders. Oops. This is why you never keep driving once the motor has clear internal problems. You're just going to make things worse - and more expensive to fix. Pull over, get it towed, and get it fixed before you do any more damage.
Here's the head - note the erosion of the mating surface due to the truck having been driven after the head gasket blew. Not good...
Here's the head gasket - can you tell which of these is not like the others?
Here's the block after scraping the gasket residue off. There is some pitting of the block surface where the gasket blew out - I figure the gasket ring material was being blown back and forth in there for a while and scraping stuff up. At least the block is cast iron, so it's not nearly as bad as the head is. Still, it's tough to say if this will hold a seal or not without a mild resurface of the block. It still seems to be flat - I can't see any light under a straightedge held across this area - but I'm a bit skeptical about putting it back together as-is and trying to run the truck, especially after paying to have the head rebuilt...
Here's the replacement engine we snagged out of a local salvage yard. It's a TBI motor, but for now we'll be using the original carb'ed intake, at least until we can find the computer, associated TBI wiring, and all the other odds and ends we'll need to convert to TBI. This engine came from a manual trans truck, so we'll need to swap the flexplate over. Anyone need a used clutch and flywheel for a Nissan Z24? :-) We'll also need to swap the AC bracket onto this motor. Luckily, the crank pulley already has the extra groove for the AC.
Here's the AC compressor off the old engine and wired up out of the way with an old coat hanger. We believe the AC system to still be charged and functional, and we'd like to keep it that way with the new motor.
The old engine just before removal. Sorry for the blurry bits. I was tired at this point and the camera didn't want to cooperate.
The flexplate and top dust cover/engine plate piece from the old motor managed to find their way onto the new motor. The flexplate (and flywheel) go on six different ways, with no hints as to orientation. The Haynes manual was silent on this, so we picked an orientation and mounted it n with a dab of blue Locktite on the bolts. We left the pilot bushing in place - no need to pull it and it's not in the way that I can see...
This is the "can you spot what's wrong with this picture" picture. See it? No? OK, it's fuzzy, so it's forgivable. This is the exhaust manifold on the new motor. It had a stub of exhaust on it that needed to be removed. We hosed down all three nuts with Kroil, but it was all to no avail. All three of them snapped off without budging one bit. Not one, not two - all three. Yikes. We'll need to yank the exhaust manifold and have it dealt with before we fire up the truck. If we can fix the other exhaust manifold, maybe we'll do that instead. This one has an extra smog hose coming off of it that we'd need to plug if we used it, so we'll see what we can figure out...
Here's the AC compressor mounting bracket on the new motor, and the motor mount bracket with the mount removed. We're going to re-use the mounts that are in the truck if possible. Since this engine did not have AC on it, we had to use a tap to clean out the four bolt holes on the block so the bolts would thread in. Oh, and the top left bolt is the long one, and top right is the short one, and the bottom two are the medium length ones. Just in case you were wondering...
Here's the old/dead motor (well, short block) out of the engine compartment and stashed in the back of the truck. Maybe we'll rebuild it, or just tear it down to see what the innards look like. It's a boat anchor for now...
The replacement engine sitting in the engine compartment and bolted to the transmission. Still lots to do, but it's in place. We had to swap the engine mount brackets from the old engine to the new one - the mounts changed from 1985 to 1986 and the engine brackets did also - so that was a bit of unexpected fun since we found out when the new engine was in the engine bay, already connected to the transmission, and we were attempting to seat it on the mounts on the frame...
The AC compressor mostly mounted to the new engine. We still need to put in the one upper bolt and tighten everything down, but it's 2/3rds of the way bolted in and won't move around, so the hoses are fine for now. That was the important part to get done while the new engine was sliding into place...
The TBI unit on the new engine. We'll be swapping the entire intake for the old one with the carb on it, but we left this on while installing the motor for the sake of getting the motor into the truck faster and because one of the engine lift points bolts to the two rear intake manifold attaching bolts...
The starter that came with the new motor is just hanging next to it and the original power steering pump and lines are just laying in there as well. We didn't disconnect the power steering stuff so we can simply swap it onto the new motor as-is and not have to worry about bleeding the system or the mess disconnecting it would have made. Power steering fluid is second only to automatic transmission fluid in the mess it makes... We'll need to use the original starter - it looks like Nissan had different starters for manual and automatic transmissions, the the new engine was originally in an automatic-equipped truck.
The TBI intake is off the new motor, and the power steering pump is mounted. No starter yet; we still had to put in the flexplate to torque converter bolts at this point. Note the metal shavings from having to Sawzall the head off one of the intake bolts... Seriously! We also yanked the oil pressure sender since it was slightly different than the one from the 1985 engine, and we'll figure out a hookup for the gauges and sender later, but before we install the intake manifold.
The TBI style exhaust (with all of it's busted bolts and extra smog pipe hanging off it) is removed from the motor. One of the studs snapped (lower rear), so we had to remove it and replace it with one from the original motor.
Mostly a repeat of the intake shot above.
The gauge panel Dad added on the inside was removed to check clearance for larger electric gauges - they should work fine with two VDO 2 1/16" gauges in this area. We'll be using an electric oil pressure and a volt gauge. A vacuum gauge will be mounted on the steering column.
The radiator, fan, and shroud are in. We had to remove the power steering pump temporarily to get room for the shroud to move far enough away from the radiator to fit a hand in there to get the fan bolted to the water pump - and even with that extra space we still skinned a few knuckles on the radiator fins... Also, the power steering mount was really tight on the front upper bolt, so we ran a drill through that hole to open it up to the next closest size - that made getting it into place much easier.
The starter is installed, and the starter and alternator wiring is hooked up again. We still have to put the wiring clip onto the trans to engine bolt just above the starter so that transmission harness doesn't flop around too much.
This is why mechanical oil pressure gauges suck, especially the cheap plastic tubing they get sold with. See the big stain on the underside of the carpet? That's where the nylon line developed a leak right where it came through the firewall. It had been slowly dribbling behind the carpet. Since the carpet has pretty solid and waterproof backer, it stayed behind the carpet and just soaked into what it could find.
The console area minus the console. Dad had tapped the lighting feed to the shifter to get the gauge lights working - that's the black wiring coming out from under the rear of the shifter assembly. Power came from a wire running to the fuse block that was jammed in under a fuse - the engine control fuse. The ground was to one of the mounting screws for the brackets for the console. Dad has also run a four socket "aux power" outlet on the back of the console. The gauge of the wire he used made this a bit dodgy, and the power feed wire had gotten pinched under one of the console mounting areas, so I removed it from the wiring. The grey wire is the new gauge feed from the new VDO oil pressure sender.
A few minor things done. The new VDO oil pressure gauge sender is installed into the block, it was a warning light contact built in so I wired that to the factory oil pressure light. The heater hose is connected to the back of the block with a new worm clamp, the fuel line feed and return (at left) are connected to the hose assembly that goes onto the intake manifold, also with new worm clamps. You can also see part of the thermostat housing with the upper radiator hose clamped to it with yet another worm clamp. Also, the wiring bracket is installed on the transmission bolt - you can tell because the wiring is running much higher on the motor than before. The wiring is clamped to the heater hose with the factory black twist clamp - those little clamps work surprisingly well.
The lower radiator hose is clamped to the inlet on the block, the upper radiator hose is installed, and you can better see the thermostat housing with the upper radiator hose clamped to it.
The new VDO oil pressure sender. The grey wire on the left is the gauge sender feed, the yellow wire on the right is a small adaptor/jumper wire to connect to the factory oil pressure warning light wire - it's the dark yellow wire at the bottom left of the picture. The actual connection is below the area of the picture, sorry. It;s just a simple bullet connector...
The back of the new VDO gauges. Oil pressure is the first one, Volt gauge is the second - you can tell by the lack of a separate sender wire on the volt gauge. The power wire is the sender wire for that one... For future sanity, the wire colors are as follows:
This is the mini-harness I built for the gauges, so they can be disconnected from a single connector if the console every needs to be removed in the future. There is one extra place in the connector, though I can't think of anything to use it for. The gauges are sitting in the correct position as they will be in the console - oil pressure closest to the driver (right in the picture), volt gauge further away from the driver (left in the picture).
Here's the gauges and their wiring that will be under the console. The wiring to the shifter light has the 20A fuse in it - that was Dad's doing; why he picked a 20A fuse is beyond me. The orange wire is connected to the feed wire Dad had installed up and over the pedals and to the fuse block on the driver's kick panel. The black ground wire goes to the nearest mounting screw for the console bracket. The grey oil pressure sender wire goes under the carpet and over to one of the holes in the firewall Dad had already drilled for his gauges. I even remembered to use a properly sized grommet on the wire where it went through the firewall...
The intake manifold and head after I cleaned the mating surfaces with a small die grinder and a mild abrasive pad. The gasket remnants were bakes on pretty nastily, and I could not get them off the intake any other way. I made sure to blow everything clean with the air hose after I removed the gasket material, and I was careful to not dig into the soft aluminum.
The replacement battery terminals, with Dad's amp gauge wiring removed. The factory wiring had one connection to the positive battery post for the starter wire, and one for everything else. Both had a simple bolt-on mount, so I ran one under each of the screws on the replacement battery terminal we bought. You can see the "everything else" wiring connector just above the AC hose in the second picture. I think it'll work; time will tell... I replaced Dad's terminal cover to help make sure there were no short-outs to the hood or any stray tools.
The intake gasket is installed along with the four inner lower bolts. These have washers on them and have different faces - make sure the proper side faces the engine. In my case I just followed the dirt and grime markings. Those holes on the manifold are open-sided, so you can lift the manifold into place, and it will slide down over those four bolts and the stud without any problems.
Here's the upper bolts - I cleaned the threads on a wire wheel before installing them so that they would thread in easily and not screw up the threads in the head. The two longer bolts go at the rear of the head and account for the thickness of the rear engine lift bracket plus a mounting bracket for one of the smog components.
Here's the intake manifold installed. The bolts only need 10-12 lb/ft of torque - don't be a gorilla! I also opted to install the thermostat and housing onto the intake while it was off the engine - note that the upper radiator hose is not yet reconnected in this picture. It's easier to do when the intake is sitting upright. Also, to get the rear lower bolt on and tightened, I had to remove the heater hose to the rear of the block and unbolt the bracket for the PCV hose that was behind the heater hose so I could push it a fraction of an inch out of the way. It was quite the chore but it got done and it all got put back together with a minimum of fuss.
Page last updated 07/26/2009 11:21:51 AM