Zed Head

Actually, the reason for the T is that both the vacuum advance and the valve on the carbon canister are operated by "ported" vacuum. So the line that runs to the TB is to the same ported vacuum source for both. It opens the valve in the carbon canister and applies vacuum to the distributor's advance module as soon as the throttle is opened. The carbon canister has a pretty big vacuum hose of its own that they must want to stay closed at idle, hence the small ported line to operate the valve.

Looks like you might have found one, although it's not really clear what Diseazd is referring to. For the record, most people who seem to be in the know say that there's no problem running a round-port head in to square-port headers. The complete opening of the round-port head fits inside the square port,so there's no flow disruption. The problem seems to be when running square-port heads in to round-port exhaust. The round port covers the corners of the square port, hindering flow.

An N47 head will work also, and will definitely have the newer valve seats. Although, I would guess that Datsun Spirit will install new seats when they rebuild it, so that may not matter. The range, in years, for cars that have that type of head is 1975 280Z to 1979 280ZX. Either N42 or N47. Might help your search. Also, if you know how much you're willing to pay, it might break a spare head free. I have a spare N42 head sitting in the garage but I'm not really in to the parts selling game. I'm still a collector, but might consider something if it was interesting and easy (shipping and all that). Good luck.

Well, even a reading at higher RPM would tell you something. Disconnect the vacuum advance, take a reading at a known RPM and people here could estimate correctness based on the centrifugal advance curve. Or, even simpler, take the distributor cap off and rotate the engine around by hand until the rotor is pointing at the #1 plug position and the points are just starting to open, then note where the timing mark is. That will get you within a few degrees of your static timing. Good luck. I get the feeling though, that you're focused on timing because you don't know for sure where it's set. If you knew, you'd probably look somewhere else for the source of the problem. My engine will idle with timing set to zero, or twenty or anywhere in between. Initial timing is not usually the cause of a poor idle.

I'm a little perplexed as to why you want to take things apart based on guesses. Why don't you take a measurement? You might find that your timing is perfect and you've been chasing your tail ("it has to be the timing") since the beginning. It could be cam timing. It could be a vacuum leak. It could be the carbs. It could be the "etc.". You should get a timing light and see what's really going on. If someone's telling you it has to be the timing and you don't need to measure it, stop listening to that person.

The OP should post more details about how he got in to the situation. Did he just do some work on the engine? What kind of work? What work besides distributor? What is the measured timing value? Jeff G, any chance that a ZX mount ended up on the 260Z distributor in your case? Maybe even in the OP's case if he started from parts. That would limit the range of adjustment.

It's just a ground wire, from the aluminum body of the AFM to a mounting bolt for the base plate. The AFM is mounted on rubber grommets so, in theory, could be isolated electrically. Someone must have taken your AFM off in the past and didn't put the ground wire back on. In reality, the rubber grommets that I've seen are usually crushed, damaged or gone so the AFM body is grounded anyway. You could check continuity of the AFM body to ground to see if you need the extra wire.

Have you measured the timing with a light? What is the number?

Just saw this today - http://www.datsunstore.com/ Apparently they're moving and have to get rid of some stuff. Says 30 cars must be sold. I thought they just sold parts. Worth a browse.

The voltmeter will always read the battery voltage, key on or off. Is that the "problem"? Maybe you just never noticed it before. The overheating, and its after-effects, might be your bigger issue. The head can warp if it got too hot. You'll find out when you get it going again. Did it overheat 12 years ago, or recently? If it's been sitting 12 years, there could be a lot of hidden problems with fuel and electrical components. They don't like to be un-used for long. If you haven't tried to turn the engine over yet, you might want to take precautions before you pump rusty gas through your fuel lines and filter, and maybe even your injectors if the filter internals have fallen apart. You can save a lot of later trouble, with some foresight now. Have fun and good luck.

Well, so much for my approach then. Maybe you have a problem on top of a problem. When it is "running fine" except for the rich mixture, it would tell you a lot if you could measure fuel pressure while driving. It should be high 20s to low 30s when cruising and jump to 36 when you give it throttle. I had a really tough time diagnosing a similar problem with my 1976 engine because the FPR caused the pressure to rise out of spec. high only when the regulator got hot. I didn't like disconnecting the fuel lines to connect the regulator on a hot engine so I only measured pressure when things were cooled off. I'm not saying that's your problem, but measuring fuel pressure while the problem is happening will at least let you know if fuel pressure is right or not. If it's right then you can move on to looking at other things.

Looking through this thread a couple of things stand out - "it ran fine until today" and "the tach needle jumps around". If it ran fine, then you can be reasonably sure that the mechanical stuff was all correct. If the tach needle is jumping around, you either have an ignition problem, as Wade suggested, or the tach died all of a sudden. So looking at the FPR and the TPS and the vacuum advance is probably a waste of time. None of those will cause the tach needle to jump around or be affected by the ignition system. Fix the known problems first, that would be my approach. You know that something is wrong with your ignition system, or your tachometer.

I don't know if it was a recall, hence my "fix/recall". As I read what Humble wrote, if you took your car in with high idle or sticky throttle problems they would either replace the AAR and/or try to clean/unstick the throttle body. Then they would do the modification to prevent it happening again. If you didn't bring your car in, it probably never got fixed. So, not really a recall, I guess.

Interesting discussion. I knew that I had read somewhere of a fix/recall from Nissan about those hoses and I just came across it. It's on Page 194 in the How To Restore Your Datsun Z-Car book by Humble. Apparently,there were two problems, a funked-up AAR and/or a sticky throttle blade. But according to the book, their fix was to route the valve cover hose to the rubber boot. Then in 78 they switched it so that the AAR went to the boot. I guess saving the AAR came out ahead of saving the sticky throttle blade, or maybe they modified the throttle body and blade in 78 so that they could handle a little bit of blow-by goo. Anyway, weird stuff. Edit - Sorry CO, we were writing at the same time. I think that the use of the T fitting is the 75-77 scheme. 1978 had the nipple on the boot, as did the "fixed" 75-77 cars. As I understand it. The FSMs, Engine Tuneup chapter have diagrams. They might have made the change mid-year though, so maybe some 78s are old-style.

Sorry for the bad information. It must be farther up behind the fan motor than I remember. I know that if you lay on your back on the passenger side floor and jam yourself up in there that you can see everything. Hoses entering the cabin, water and vacuum cocks, etc. I've had luck looking around corners with a mirror and a flashlight, if you want to try to get a peek before you commit to getting stuck. If you squeezed the hose from the engine bay, maybe it can be reached through the hole from the engine bay. Just a thought, the nipple might be right there on the other side.

Sorry silvey, but reading your posts is like reading gibberish. Can't tell what you've done, are doing, or trying to say. There is plenty of information out there about the slave cylinder and how it can go wrong, how to check it, and how to fix it. Good luck.

I went back to your first post and realized it's not clear if the clutch has ever worked. I kind of assumed that you had put the 5 speed in and were having problems. The first thing that I would do is remove the rubber boot on the slave cylinder and see if there is brake fluid inside (brake fluid is used for the clutch hydraulics). If there's fluid inside, you need a new slave cylinder. It's common to get some, but not all, of the stroke when the cylinder starts to go bad.

Some of the 280Z's, maybe all of them, have a vacuum controlled water ****. Apparently, there's an on-off water **** (the vacuum controlled one) and there's a flow control water ****, the one with the copper tube that runs to the heater core. Regardless, if you stick your head up under the passenger side dash you can see both. Removing the glove box might be the easiest way to see and work with them, without removing the dash, if you don't want to do the yoga.

It sounds like your battery is only connected to the starter and the EFI harness and the alternator is only connected to the fuse box and body harness. The battery starts the car and the alternator runs the body electrical when it starts charging. The alternator behavior is like a GM one-wire setup, which requires revving to get it to start charging. The charge light probably comes on because the L wire is not connected because someone has set up the "simple" (primitive) one wire alternator. The voltmeter's in the Z cars are not known for accuracy so the 16 volts is kind of meaningless, you need to use a real voltmeter. But before you do that, you should fix your wiring, it sounds messed up. It could be as simple as connecting the white charge wire from the alternator to the starter terminal,where it will be able to charge the battery like it's supposed to. Or it could be a nightmare wiring mess from a PO.

You didn't give any details about the clutch parts that are in the car. Are they the 240Z parts or did you install a 280Z clutch to match the 280Z transmission? Actually, extending the rod probably won't help. If the rod was too short, the slave cylinder piston would just pop put, unless the rubber boot is retracting it when you release pressure. I would loosen the rod adjustment nuts, push the rod back in to the slave cylinder, and re-tighten. The other possibility is your pressure plate and collar combination. Edited...

Do you have a good idea of how the clutch works? You haven't responded to Posts 2 and 4 and you're asking the same question over again.

Blue just gave a number in this thread - http://www.classiczcars.com/forums/showthread.php?t=47300&p=410213#post410213 The numbers on the bell housing won't tell you much, and won't have much to do with how your clutch works. It's the combination of pressure plate and throwout bearing collar that matters. Tell some details about what clutch package you started with and any changes you made when you put the new transmission in. The transmission looks like a 77-79 "early" "wide ratio" 5 speed, by the way. I see that you have the adjustable rod from the slave cylinder. Have you tried extending it yet?

I had a brand new slave cylinder that leaked in the middle of its travel. It moved correctly, when viewed by eye, and actuated the clutch but when it got warm it would leak more and I would get less travel. Grinding reverse, hard to get in to first, etc. The problem was sporadic like you're describing so it was hard to diagnose. I knew I had a leaking cylinder though, when I took the rubber boot off of the slave cylinder and it had fluid inside. Take yours off, it should be dry inside. If not, get a new slave cylinder and take it apart and clean the insides before installing. The quality control at the manufacturing plants is poor and some of them get shipped out with machining and honing grit inside which tears up the seal.

A leak down test would identify a leaking valve. At least do a cylinder pressure (compression) check. You're jumping way ahead to an expensive conclusion. You might just need a simple tuneup - plugs, rotor and cap.

Valve lash set too tight or eroded valve seats from unleaded gasoline could cause a burned valve. When the valve doesn't seal completely hot exhaust gases squeeze through and erode the valve and valve seat material or warp the valve from uneven heating. Then the valve doesn't seal well at all, you get compression loss and it's all down hill. If the valve is burned the valve seat is probably bad also. You would have to remove the head, replace the valve and install new valve seats. If you have one burned valve, unless you made a mistake setting valve lash on a single valve, it's probably time to rebuild the head.