Captain Obvious

Weird. No, I don't have an obvious answer, but here's some musings. There's no guarantee that all three cylinders fed from the same intake manifold get exactly exactly the same percentage of input stream, but they've got to be close enough to not result in that. All those Z's on the road running carbs with the stock intake... I'm no expert, but I've not heard a contingent of people complaining that the intake manifolds were designed such that 3 and 4 run twice as rich as the rest. Those clean plugs don't look like they've got anything at all on them. Like they're still brand new out of the box. After ten minutes or so idling, I would expect to see something on all of the plugs. I can't see anything in the pic... Is there at least something on all of them? Maybe the root problem is with the clean plugs, not the dirty ones? I would confirm that all the cylinders are firing (probably by pulling spark plug wires while the engine is running or some other potentially dangerous method). Pull and ground each plug wire in turn and verify that the idle RPM goes down and gets rough? Don't get zapped, and don't burn out your ignition system by running OC. I would also check the valve lash and run a compression test. Make a note not only of the final peak compression pressure, but also make note of (about) how many compression cycles it took to reach that pressure for each cylinder. If four cylinders take three revolutions to get to peak, but the other two take ten cycles, that could be a clue.

So trying to pull this back on target... Assuming we can shake down the bugs in our intended 260 ride and make it to the event without having to push the car, I'd be happy to demonstrate a set of flat tops on a stock 260 engine. The doubters can sit in the passenger seat with a big grin on their faces. This car was pulled off the road maybe twenty years ago, and has since been the subject to a significant tear down and rebuild of pretty much everything but the engine. It's seen maybe a hundred miles since being put back on the road. So what's the smart course of action? Jump in in and drive 2000 miles round trip, of course!!

As Henry McCullough once said (while talking about money) - "I don't know, I was really drunk at the time". You be the judge.

OK, fine. I put up a different pic.

Oy. Moving right along... Thats not MacGyver esque.

I can feel the flat top love from here. Getting stuff ready for the trip:

Hahaha!!! You've obviously seen my toolbox! So before this thread goes completely off the rails... Hopefully the fast track shakedown of our intended ride goes well and there won't be any pushing involved. Hope to see all of you soon! Friends old and new!

Ummm... Yes? You don't pay me enough to push.

So I had forgotten that I had these snippets from the FSM that relate to that check valve. Had posted them somewhere on some thread prior. Details have faded. In any event, mention of the check valve started in 76. I don't know if it existed in 75 and they just didn't mention it, or if it was a new device added in 76. Here's the location on the car: Here's how it looks in the system schematic. This is from the 78 manual. Previous years had a similar pic, but 78 is the most accurate: And here's how you are supposed to test it. Note that this test procedure didn't appear at all in the FSM until 1978. It describes a device which allows air to flow easily ("smoothly directed") from the carbon can back to the tank, but dictates that it should be harder to push air from the tank towards the carbon can. They say "considerable resistance" towards the carbon can. My interpretation is that "considerable resistance" could cause a woosh:

Nissan wasn't very good at labeling the wire colors on the device side for many of the small devices like this. In other words... I wouldn't be surprised to find that the wire colors on the harness side are correct on the diagram, and they were just never identified on the device side. I would guess that the creator @wal280z of that colored wiring diagram probably just assumed the wire colors did NOT change since there wasn't any info to the contrary. So... Is there a three position connector hanging down between the tach and speedo that has black/yellow, green, and black? If so, that's where that buzzer plugs in, despite the color change to a pair of reds and a black.

Yeah, me too. But it's consistent. By that, I mean, it seems to build up pressure to a consistent pressure and then level off. Based on that, I believe it's working. Well that, and my tank hasn't ballooned out from overpressure.

Second. On my 77 it is under the car close to the fuel pump and I would also assume that 76 is the same. That said... It's a check valve, but it will build up pressure in the tank until the "cracking pressure" of the check valve is reached. I don't know how big of a woosh you get, but I get a significant woosh on my car. And I believe it's working properly.

Winner!!

Oh! Well that's good! Thinking they were still out there, I was starting to feel bad about the time I spent making my new one. Now I'm happy again! Plus, now I've got that sweet tube beading tool for the lathe.

Strike one: Strike two: Third pitch... fouled off Base hit!! Haha!! Yes, it's the annoying buzzer/beeper. Supposed to make noise when a) the key is first turned to the "ON" position (beeps six times or so and then stops), and b) anytime the key is in the ignition and the driver's door is open

I'm sure you'll figure out the wiring. It's not going to be fun though. Red/blue and green/white is almost always dashboard/console illumination. The other colors are harder to pin down. You'll get it. So about the feedthrough for the firewall on the heater... I didn't even know you could still get that part new. Was it expensive? I made my own because I didn't think I could even get it. Well that, and I made mine out of stainless just because I could.

Haha!!! So it's a shame that some of you guys won't be able to make it. For those of you who are still on the fence, here's to hoping you fall on the Zcon side!

I just heard that the shift map is cracked, so I'll step aside and let subsequent interested parties have a shot. Naaa, but thanks! I was just interested in messing around with an un-cracked shift map. I've got a couple already, but I think everything I have has some sort of defect.

And somehow I think I missed your completely heater core and valve assy. Looks great. Is that a new feedthrough tube for the firewall? Was turned down ninety and you cut it off to make it straighter? You're probably going to want some sort of flow restricting device somewhere in the lines besides the new valve. I found that after making mods like this, the flow through the heater core is way more than ever necessary. I believe the original temp control valve was much more restrictive than the new style ball valves. You may want to cut the flow down somewhere else with a fixed restriction.

Woof. That harness is going to take some sorting. Going through someone else's electrical work is always a real treat. The first group of hacks is clearly headlight related. The second set... Not sure. Hazard? Radio? In any event, you've got your wires cut out for you.

Can't quite tell from the pic... Is that a crack on the left side of the shift map on the OEM knob? Over on the 1-2 side? If it's not cracked, I'll take it.

I wouldn't rewind anything unless I had a reason to believe I needed to. I would give the field windings and armature windings a good visual and if I didn't see anything troublesome, I would put them on a fixture to check the resistance and make sure everything was in spec. Would probably also hi-pot test to check for leakage and/or shorts between windings. If everything there checked out OK, I wouldn't rewind anything. And I can assure you from the costs that are being charged... The rebuilders aren't either. Think about it this way... RockAuto is currently selling reman units from seventeen to fifty-five bucks. Seventeen bucks!!!!! How much labor does seventeen bucks pay for?? It's all labor since you are sending back a core. They put labor into the core and send it back out. Even at fifty-five bucks... How much labor do you get for that? Certainly not enough to strip, rewind, and varnish field windings!

I'm in along with my local buddy Gary @GGRIII. The plan is to drive down in his flat top fueled 260.

Well I'm not in the rebuilding business, but it's clear from the costs of the remanufactured parts that they simply can't be spending a whole lot of time one each one. It sounds like you are a lot closer to the reman sources than most of us and you would have a better chance of providing some real input here. If I were in that business, I would do as little as possible to get things turned around and back out the door. Based on the costs involved, they can't be spending more than fifteen total minutes on each one. New bearings and brushes, some quick plating, check it on "the test fixture", some crappy paint and into a box before the paint dries. Have you asked your supplier for a description of their rebuild process? I have no doubt that it would sound completely credible and reasonable. Which begs the question of why the failure rate is so high and the reputation is so bad. I am much more confident in my own work. Might not look as pretty because I'm not going to re-plate anything, but I would use bearings who's lineage I could trace, and I would make sure the brushes ran true on smooth surfaces. I've been into at least ten alternators in my automotive past and none of them ever needed any more attention after that. In fact, the one on my 77 is an internally regulated 83 version that I "rebuilt". It's been trouble free for a couple years now.

And that's what it's all about!