Zed Head

Could also be that some valves got bent during head installation. A cylinder pressure measurement will show that.

Who rebuilt and installed the head? Is it the one the car came with? Your PCV hoses look right, I couldn't see that the one in front of the AFM was an elbow. I'm afraid you have the typical internet dilemma of assuring everyone out here that things like cam and ignition timing are "right" and don't need to be verified, yet you can't get the engine to run right. It's hard to get too involved when you don't have verification of those important things. No offense, but the thought that runs through your mind is "why should we believe this guy"? Anyway, two things that come to mind are: 1. a rotten EGR passage, where the blockoff plate doesn't work because the passages themselves are rotten. Somebody had that problem a few years ago and he had all kinds of odd problems with the way the engine ran. I think that he might have found it by measuring intake vacuum. It was much lower than it should have been. You might take an intake vacuum measurement since it is a measure of how the engine is pulling iar through the manifold. It's a clue. 2.

Here's your other thread, in case anyone thinks they've seen this one before. Reptoid is right, there's something off about your PCV system. Looks like the valve cover is open to the atmosphere. That's not good.

How about a description of a normal cold startup, warm up, then the driving experience? It's hard to tell what is really wrong. Make sure you distinguish between tailpipe "backfire" and carburetor popping. Does it just not "go", or does it go with a lot of bucking and back or front firing? A video would be great. You can tell a lot by how an engine sounds.

Which Pertronix do you have? There are two. I don't think that you need the ballast if you're using a 3 ohm coil. With either of them. That's going to give you weak spark probably. https://cdn.shopify.com/s/files/1/0247/6913/4628/files/1741.pdf

If you don't do excellent work on the modifications you'll reduce the value of the car considerably. Early 240Z's with originality are getting good money on the auction sites. Just something to be aware of. https://bringatrailer.com/datsun/240z/ Here's a silver on silver on silver car. https://bringatrailer.com/listing/1973-datsun-240z-153/

Sorry, I don't recognize those. Looks like he has his garage set up as a showroom. Or maybe that's his living room. Dan Tanna style. Just realized that there are other "zedhead"s. Mine has a space between.

The raw version. Thanks gwri8, that was interesting.

Three drummers. WTF. Look at those guys...Shaver's Live Forever.

If air flow drops low enough the fuel pump will shut off. That's what it is supposed to do. Yes, the idle screw on the throttle body. If idle speed doesn't increase that's not right. If the engine dies when it's closed that's a sign that there is no vacuum leak. The backfire makes me think of incorrect timing. Any chance that there is a hole in the tube between the AFM and the throttle body? If the engine is pulling air the AFM vane should move. The tube between the AFM and throttle body needs to be sealed. Last thought - has the AFM spring been messed with? If somebody tightened it it might not move fast enough to let the engine rev. When you open it by hand you're telling the ECU to give more fuel.

Your 77 would have the AFM fuel pump switch. You might try turning up the idle speed to see if it will stay running once it warms up. More iar keeping the vane off of the switch. If it keeps running after warmup with a higher idle speed it will be a clue. Not really sure what this means either. Kind of sounds like a blockage in the intake system. Mouse nest, rag, etc. It should rev just fine even when cold. So the advice above might be irrelevant.

The AFM vane should move free and easy, in concert with the throttle blade. When you "redid" the engine and components did you modify anything? PCV tubes, maybe? All air must pass through the AFM. The PCV system is connected to the intake system.

Looks good to me too. I had KYB's and liked them a lot. CO's comment about urethane on the T/C rod is good, it will steady the steering on hard braking but he'll never notice otherwise. You might go with urethane on the steering rack also, it will tighten the steering up a little bit.

I'm not 100% because my brain doesn't mesh with whatever Nissan means with their newer-former-superceded interchange lingo but I think that they're saying "Yes". Not really sure though. They left some boxes unchecked I think. http://www.carpartsmanual.com/datsun/Z-1969-1978/steering/steering-gear/2

Seems like the Nissan part number might give some info. It doesn't match the Z numbers. But that doesn't mean a ZX part didn't supercede it and is interchangeable. We need a CarPartsManual for the ZX. http://www.carpartsmanual.com/datsun/Z-1969-1978/electrical/radio-stereo-clock/stereo-(from-aug-76)

I used a Sharpie and put you in the Eastern zone. Just wondered if you saw some tornadoes. The news showed real houses getting hit instead of the usual trailer parks.

Here is one of my old emissions test in Oregon. It's idle only. What's weird about yours is that the CO is low but the HC is high. I seem to remember that if you had incomplete combustion your CO should be high also. I wonder if your problem is oil related and not fuel. Maybe leaky valve seals or rings. You might give it a good "Italian tune up" right before you go in to warm up the seals. Fail on top, then Pass, below. CO was the last thing i had to get tuned in, which I did by the idle air screw and lowering fuel pressure. They change the format for the printout, sideways for a Fail, up and down for a Pass. You can see that as I leaned things out the CO and the HC both dropped, but the HC was already okay. HC came in first, then CO. Or, as I think about it, the other possibility is an ignition miss. That produces only HC since there is no combustion at all. That actually seems more likely. CO shows combustion that started but did not complete, HC shows no combustion. Full combustion should convert the CO to CO2. With an ignition miss the gasoline (HC) passes right through along with the oxygen that is supposed to combining with it. Just thinking in print. I'd check those plugs and plug wires.

Are you on tornado watch? Isn't it, like, 2 am over there?

If there's no coolant in the engine it might be that the coolant sensor is getting "steamed", and showing 212 F , from condensing steam, instead of the true temperature. So when you try to restart it's too lean. But that doesn't explain the WOT starting procedure. Not sure what's happening there. You can run straight water with no problems. Are you missing a radiator or something? Another possibility is that the ECU is going bad. I mentioned this earlier but that's one way that they die. They flood the engine to begin as they start to die, then eventually they just don't do anything. I had a 78 ECU do that. It died while I was out testing it, then restarted, then died twice more as I tried to get home, then wouldn't start at all. I put the stock ECU back in and the engine cranked right up. Never really figured out what was wrong with it but I assume that something inside overheated due to current flow. You'll find a bunch out there about ECU's running rich due to bad solder joints. One quick fix is to bang on the side of it. Apparently that really works. Your 75 is the first year of the ECU's so might be the most likely to do that. If you can find a loaner or a cheap one to buy, it's always good to have a spare. Any of the 75-78 ECU's should work.

Have you opened up the idle air screw on the AFM? That's what it's for, at least for idle. I don't know how much effect it would have on 2500 RPM. But your numbers are actually really close I think, it might get you there. Take note of how many turns out it is so that you don't get lost in your adjusting, and can go back to the starting point. Then open it up until you get a miss. Then pick a spot in between and try the test again.

Turbo day. Seems like a low start, but seven bidders. Edit - there was one more bid after I posted. It sold for $8,500. https://bringatrailer.com/listing/1982-datsun-280zx-turbo-12/

Not clear what year car you're working on, and if it's California or Federal. Some have two pickups in the distributor so that timing can be changed at a certain coolant temperature, for emissions. Kind of sounds like that might have happened. Might also be combined with a bad ignition module, one circuit might be bad. If it does it again, you can disable one side and let it run on the good circuit.

75 was the first year of EFI. Might be that they changed it later. Looks like it's either on mine.