Zed Head

I would be careful on material with the o-ring. Plain old plumbing o-rings might absorb brake fluid and swell (I tested an Ace Hardware o-ring to see if it could be used - it swelled). Viton would be fine if you can find them. I don't know what the typical material used is, and most manufacturers that I've seen don't list it. It's a problem.

The 75 files are 86 MB total. Have you taken any of the resistance measurements shown from page 45 on of the "bible"? The three tools that will help you the most are a multimeter, a timing light and a fuel pressure gauge. Without those, troubleshooting will be difficult.

The problems you described and the actions you took don't really follow, and the description is a little confusing. You said that the pump kept running when you turned the key off then the engine started running rich. But the engine can't run with the key off....? Plus you're on the "changing parts" path, instead of the "test and take measurements" path. Nobody can recommend a new part to change until you've taken a measurement. First, I would download the 1975 FSM and use it instead of the "bible". The "bible" is like using Cliff's Notes, when the original book is right there, and free. Read the Engine Fuel chapter. I would measure fuel pressure and record the resistance of the coolant temperature circuit. Those are two things that can easily cause a rich condition. As far as the pump goes, the wiring diagram is in the Engine Fuel chapter also.

I think that what's bothering some of us is why you aren't worried. Can't figure out why you're so confident, when you can't even get the gasket material off of the head. Maybe you're just okay with problems if they do come up, you'll just take it off and start over. Can't say that I haven't taken some chances like that myself but you seem a little over-sure that all will be well. Looks like an interesting adventure though. Good luck.

I didn't know the internet would turn the link in to an advertisement. I was referring to his comments about quality, in the text on the page - "We've seen a lot of problems with a lot of different less expensive syncro rings for these transmissions. Years ago we decided not to install or sell them anymore. No one likes having to do a job twice because of junk parts. We've never had a single problem with this style. Be wary of less expensive syncro rings." It may be that not all baulk rings are the same. But, as gnosez says, maybe it depends on how you intend to use the transmission. As far as cost, Nissan charges about the same as zspecialties for one ring. But I don't think that Nissan sells a kit, although you can get bearings and seals individually also.

The comment on zspecialties' site about the synchro rings is interesting. Oliver, the owner, might be worth a call or an e-mail. He's been helpful when I've talked to him. Syncro Ring 1st through 4th 70-83: Drivetrain Z - 40124-EPDT - Z Specialties Online Store - If we don't have it in stock, we can get it!

Everything seems consistent. What is there to disbelieve?

Did the head come complete, with cam, rocker arms, etc., from a running engine, with the new steel valve seats already installed and broken in? Or did you remove the valves and replace the seats? Did you keep the rocker arms, valves and assorted pieces in the order that they were taken out? Just curious, since you might have other problems when you try to put it back together. A little bit of heat would probably soften the old gasket material and make it easier to remove. Makes some people nervous but the gasket will soften up well before any damage is done to the head. A heat gun would work if a torch is too scary.

Don't know if it will affect your decision but that is an F54 block, so might have flat-top pistons, if it came from an NA car. If so, with the N42 head, the compression ratio will be higher than the stock L28. Either way, the head did not come with the block, and the "E30" cam did not come with the N42 head, so somebody has put together their own set of parts. That's not a typical L28 engine.

Flat, straight and parallel is more important than clean. Along with the critical dimensions of valve seats, guides, etc. You're focusing on the wrong thing, if you plan to use the engine to make the car move.

That's probably the best picture of the housing out there, I always forget where it is. Eurodat's probably right, it's just an extra transmitter. Measure the resistance from the bullet connector to ground. If it's a transmitter you'll get a number, if it's switch you'll get zero or infinite.

You might have a 76-77 thermostat housing. 76 for sure has four - thermotime switch, coolant temp. sensor (for ECU), coolant temp. indicator (for gauge) and temp. switch for the ignition module (to use the second pickup in the distributor to advance the timing when cold).

No editing allowed. Weird. Didn't mean to sound harsh above, but a good mechanic should know about the return line on a pressure regulation system. "Discovering" the return line is a bad sign.

There's a diagram of how the fuel system works on page EF-5 of the FSM. You should find a new mechanic. And have the new one measure your fuel pressure.

When I peeled my half-cap off the silicone stayed behind on the dash. The installer had only laid a few lines of adhesive down though. I was able to remove most of it, but I still have spots that are stuck permanently. If you're going to be sanding and resurfacing it probably won't matter. Peel up an edge and see what happens. Get the interior nice and warm first though, the cap is made of ABS or a similar plastic and will crack if it's stressed cold. In case it doesn't come off easy and you change your mind, or you want to try to resell it. Otherwise, just break it off in chunks.

Stick some stiff paper or thin metal sheet between the dash cap lip and the edge of the gauge to make a ramp. Spray a little Armorall or spit on it for lubrication. The plastic will stretch a little, make sure it's not too cold so you don't crack it. I slipped mine out the first time I took them out, with a half-cap. Since then I've removed the cap and see the cracks as character.

More likely that it's stuck open, causing the ECU to supply more fuel. You can check by looking at the bumper for the damper weight under the black cover on the side of the AFM.

The things that you tried that raised the idle that made it run better all leaned out the mixture. Removing the AAR hose, taking off the AFM boot (AFM signal disappears), taking the air screw back (bypasses the AFM vane). Somehow you've made things too rich. Did you adjust the AFM spring? Accidentally knock the coolant temp sensor connector loose? Raise your fuel pressure somehow? You might also have fouled some plugs. Brake cleaner is not designed to burn, like carb cleaner is. The old brake cleaner won't burn at all, I don't know about the new "green" stuff.

You said it ran well with the hose between the AFM and the air filter removed. The only thing between the AFM and the "air" is the filter and the plastic tube to the air intake point. Did you check the rest of the intake system. Maybe you meant the hose from the AFM to the throttle body? If so, it sounds like your AFM vane is stuck closed.

Clogged air filter?

The boiling water method works. The bushing is made of nylon, which absorbs a lot of water. The absorbed water plus the heat soften it up and it will pop off. Boil it, then try the adjustable wrench method while it's still warm.

Looks like Nissan may have them, for a couple dollars more. If "insert" means seat. Look at parts 5 and 6 - Datsun 280Z Cylinder Head, Rocker Cover & Thermostat L28E INSERT-VAL :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com

Coincidentally, today I was looking at a few ECU's I've collected to see if they had the "altitude compensation" pins. All of them are A11-600-000 and they come from cars from 76-78. While checking the FSM's I saw that only the California cars came with altitude compensation. I wonder if the -601- ECU's have the altitude compensation circuit? Samson is in CA, Eurodat, where did your car, or ECU, come from? The switch is described and shown in the Engine Fuel chapter, it drops the fuel supply through the injector duration by 6% when the switch closes due to low pressure from high altitude. It wouldn't affect operation unless the switch was shorted, causing a lean condition. Samson, your mechanic doesn't understand how the injection system works. The injector connections have 12 volts on both sides due to the way the transistors operate (I confess that I'm not clear on why that is either, but it is). The injector solenoids don't activate until current actually flows when the transistor circuit allows it to. 12 volts on both sides is good. As I said in an earlier post, you're pretty close. I had to adjust my idle air screw and install some new plug wires on my last DEQ (our emissions checkers) visit here in Oregon. A miss will spew unburned fuel (bad), and the idle air screw can lean up the idle. I wouldn't do anything major and I would find a mechanic who knows old EFI.

Whoever suggested the AFM as the problem might have been thinking of 75-77, which have the fuel pump contact switch. Your 78 should be useing the oil pressure and alternator current to activate the fuel pump circuit. But the fact that your fuel pump has been rewired to be on with the key at On takes the fuel pump safety circuit out of the picture anyway. Here's one possibility - whoever rewired your fuel pump to come on when the key is at ON, bypassing the safety circuit, might have it wired so that it actually turns off when the key is at Start. Turn key to On, pump turns on, pump turns off when key is turned to Start, engine fires then dies because fuel pressure dropped, fuel pump comes on again when key is released, second try works. Just a wild arse guess and still doesn't really fit what's happening well. Your symptoms are weird so even the troubleshooting chart will be difficult to use. The first thing you might do is determine if it's spark related or fuel or electrical (loss of power to the EFI system). Get one of those flashing spark testers for a plug wire and watch what happens on the first start, if spark disappears before the engine dies that will tell you something. Or measure fuel pressure while starting. Or use a Noid light (I still don't really know what noid means) or christmas tree light and see if the injectors stop firing before it dies. Don't buy a new AFM or CSV. The symptoms don't fit.

I think that the ECM gets its signal from the negative post of the coil, not the ignition module. Are you sure that you're getting spark? No spark = no ECM signal = no injector grounding through ECM transistors. Of course though, the same applies for spark - no reluctor pulse from distributor to ignition module = no spark = (see previous). That's the chain of events, assuming that you have distributor-controlled timing and not a CAS (you have a ZX right?).