Captain Obvious

What Blue said. When you lift the piston with the little test rod, you disable that carb. So when you lift the front and nothing changes, it's because the front carb isn't doing anything to run the engine and those front three cylinders are just along for the ride. When you lift the rear carb and it dies, it's because the rear is the only carb that's adding fuel and you're running on just the rear three cylinders. If the needles are installed properly (with the shoulder flush with the bottom of the piston), and the nozzle adjustments are turned all the way up (zero turns down), and the nozzles are fully seated all the way up (not stuck down or held down by the choke system), and everything is in good shape (not worn or corroded away), Then I would expect it to be so lean at idle that wouldn't run at all. So again, what Blue said. The fact that the front carb isn't running the front three cylinders with the nozzle all the way up is probably a GOOD thing. If the rear carb is still supplying enough fuel to run the rear three cylinders even with the nozzles all the way up (and even smoke at that!), then that rear carb is most likely a problem. As for checking the needles and nozzles for wear or oval shape? If it's so bad that you can see it with the naked eye, then it's really bad. I can tell under magnification with measurement tools, but I don't have a quick and easy way for you to verify. How much do new nozzles cost? Can you borrow a pair from a known good set of carbs just to see what happens? You're positive you've got the needles installed properly, right?

Yeah if you've got fuel pressure on the needle and seat even with the engine off it's possible that you're bleeding that pressure off into the bowls slowly overnight and starting flooded every morning. The original system with it's orifice based regulator allowed the fuel pressure in the rail to drop to zero as soon as the pump stopped moving. Sounds like your new setup doesn't allow that and you're asking your needle valves to hold that pressure back 100% forever and I'm not sure they're that good. Especially if you're getting a heat soak induced pressure spike after shut down. It might be part of the problem. But that won't cause the long term high fuel consumption while driving though. That's got to be an adjustment or needle or nozzle issue. Keep in mind that the needles and nozzles can look fine to the naked eye and still be out of whack. My experience is that five thousandths (.005 inches) was enough to make the difference between purring like a kitten and stinky eye burning exhaust. If you've got any doubt as to the condition and you've exhausted all other possibilities you might want to think about replacing them. 115 miles to a tank is certainly low.... BTW - How do the plugs look? Are they also indicating a rich condition?

It sounds to me that you're thinking the needles cause the fuel level to rise when they are inserted into the nozzle? If that's the case, you have to remember that unless you pulled the needles out first with the fuel pump still running, the fuel level was established with the needles submerged. That means the fuel level will go down a tiny bit when the needles are pulled out and then return to "normal" when they are reinserted. And the amount of that change (either up or down) is only by the volume of fuel displaced by the portion of the needle that is submerged and that volume is very small. The needles are not splashing fuel up into the venturis when the pistons drop. If you've got fuel puddling in the carb throat, it's not because the needles splashed it there or caused the bowls to overflow because the volume of a submerged needle raised the bowl level. That said, how are you regulating fuel pressure and what does that fuel pressure do when the engine is shut off? I'm wondering if the pressure goes up higher than intended when the engine is shut off and the fuel in the rail expands from heat soak. Are you sure that you're never exceeding 3 psi at any time? Ever? Also, when you found fuel puddled in the venturis, how long had the car been shut off? I know you said you ran the pump with the pistons out and the level didn't change, but if you're looking for a slow leak and the car sat overnight? You could have a small seep around or through the needle valves that you don't see with the naked eye, but over a 12 hour sit maybe it adds up? And about the poor fuel mileage and only getting 115 miles to a tank... Are you sure your needle and nozzles are in good shape? If they had been rubbing in the past or if material has left through corrosion, that will throw everything off. It doesn't take a lot of material removal to have a big impact. If you ovaled your nozzles and/or grooved your needles, then you could be sucking down way more fuel than intended even if the bowl level is correct. Bottom line? My suggestions: 1) Check and set your bowl levels with a clear tube on the bowl outlet. 2) Put a fuel pressure gauge on the rail and make sure the pressures are what you expect at ALL times. 3) Inspect your needles and nozzles very closely for wear or corrosion.

Gotcha. My original AAR didn't work right either. It was mechanically fine, but electrically intermittent. Anyway, welcome aboard and glad you got your car running well. Here's hoping you get to the bottom of the rest of the running rich issues.

There's good info on the AAR in this thread: http://www.classiczcars.com/forums/fuel-injection-s30/47447-help-me-understand-aar-please.html About a third of the way down, there is some discussion about the screw together AAR versions (Look for TomoHawks posts) . Some with two tubes like you posted above and some like one I nabbed off a Pathfinder that has one tube and a hole in the mounting face that ports air right into the intake manifold. I assume you searched around for aar stuff and that thread didn't show up. I couldn't find it with the search function... I'm guessing that "AAR" is too short of a keyword and it doesn't work? So about the mixture running lean if the AAR is ported to atmosphere... If you're running too rich for some reason, then having the AAR artificially lean the mixture will be a positive, right? At least until the AAR heats up and closes. And then you're back to your original rich running anyway. So what was your original AAR doing (or not doing)?

I've seen plenty of flexible of PCB's but never out of fiberglass/epoxy. Nothing wrong with trying, but I don't think it'll take enough of a set unless it was molded like that originally before the epoxy set. The thread reminds me though... I've got a buddy working on a LED third brake light project. Maybe I should poke him and see how that's coming along.

Cool. I've been continuing to think about this and I'm still thinking you need to take a close look at your fusible links. The more I think about it, the more an intermittent connection to the black link makes sense. Your old alternator tested good. You put in a new one (that's presumably good) and the problem "went away". But my concern is that the problem was intermittent all along, right? Sometimes it was fine and sometimes it was screwy? I'm worried that the link is currently making a good enough connection that the problem is not bad enough for you to notice, but intermittent connections are like that. Intermittent. I guess what I'm saying is that I'm glad you got the car working, but I wouldn't be surprised if in a couple days from now you come back and say it's doing it again. Hoping not, but wouldn't be surprised!

Good luck and keep us posted!

That won't work right. The AFM won't know about the air being supplied by the AAR and you'll run lean until the AAR closes.

Haha!! Yes you did!

Well that's sorta too bad that it passed. Makes it harder to find the problem. Next thought is that the alternator is doing what is expected of it, but the fusible link connection between the alternator and the battery is shaky. I haven't studied it that closely, but it appears that the alternator will still run certain parts of the car even if that link is gone, but things like the headlights and the FI will run off the battery and not off the alternator. And if that connection is intermittent, you'll get swings on the voltmeter on the dash as the alternator is intermittently presented with the heavy load of the battery. And if that link is making connection, but not a good one, it's likely to heat up right at the connection ends. So... You've got four fusible links in the engine compartment on the passenger front wheel well. Three of them are one color and are smaller than the fourth. My 78 FSM is blurry and it's hard to read the wire colors, but I believe the three smaller ones are brown and the fourth larger one I black? The one I'm concerned with is the black one. With the engine running and a meter on the alternator output, wiggle that black link around a little and see what the meter does? If that fusible link doesn't make good connection the alternator won't charge the battery correctly. If you see anything funky on the meter (heck, even if you don't), pull the link off and make sure everything looks clean and shiny? Not green and crusty. While you're in there pull all the links and make sure they're all nice and clean. Just make sure you don't mix up the colors.

TomoHawk, The original festoon bulb is what they considered a 31 mm festoon, but that's measured tip to tip, so it's hard to draw any correlations without actual drawings of LED replacements. I measured the two lamp housings I have here and came up with the following: Distance between the inside edges of the brass contact clips = 0.67 inches. Distance between the plastic inside walls of the whole housing = 1.47 inches. That means in order to fit comfortably into an unmodified location, the wide PCB portion of the bulb must be less than 0.67 inches wide, and the overall length of the whole bulb (tip to tip) must be less than 1.47 inches. That bulb you linked to on Amazon looks very promising mechanically. It looks like it would fit better than what I used and I don't think you'd need to modify the contacts. If you could get that in warm white, it looks like a winner. I bet the ones on Amazon are cool white though (what you're calling hyper). The bulbs I used with the PCB turned the other way. You can see from the dwg why I had to remove some material from the clips to get the PCB to fit. I also had to file a tiny bit off the tips of the cones to get it to fit inside the plastic housing, but it was a small amount and very easy to do: Maybe you could dig up a mechanical drawing for the bulb you found?

Wait a minute. I want to make sure I'm doing the math right... I can give up the wife for a car like that?

I can't see the control signal tubing at all. I suspect it's been removed and disabled ever since he swapped in the older SU's. There is a vacuum port on the original rear flat top carb that is a ported signal. "Ported" such that there is no vacuum at idle or at WOT but only at a point between the two at "light cruise". That signal is what was originally used to control the amount of EGR. The round top SU's have no such vacuum connection on them at all, so I assume that control line is simply capped off rendering the whole EGR system inert. There's a small electric solenoid valve between the EGR control valve and the valve cover. Can't see it in your pic because it's tucked behind the device you were curious about. That's also part of the system.

Yeah, those will work fine but aren't stainless. No biggie, but I just prefer the OEM style.

I was originally going to suggest that it's easier to pull the whole dash first. If you've got small hands and are part contortionist it's not "really" necessary, but I've found the extra time I spent pulling the dash was more than made up for by the ease of working on the heater system after I had done so. No matter how you look at it, pulling the heater core out is a PITA. I feel for ya Charlie. Be careful of your back.

That's the EGR control valve. (EGR started in 73 which is why your 72 didn't have this device.) The purpose of the EGR system is to reduce oxides of nitrogen (NOx) from being released into the atmosphere which is a good think for the next generation. There isn't really any performance reason to remove it. It's only active at light cruise and is disabled at higher throttle positions. Looks better without it, but no reason to do so for performance. I'm assuming he's still running the original carbs? Because if not, I'm not sure where he's going to hook up the ported control vacuum signal...

I couldn't get the ebay link to open, so I can't tell for sure, but I've never seen small hose clamps that were as good as Nissan OEM. The OEM ones are full stainless and everything I've ever run into aftermarket was at least partially plain steel. If the ones on ebay aren't 100% stainless then just go to a junkyard and grab a handful off Sentras and Maximas.

Glad to (try to) help. My additional advice would be to take it to SteveJ's place and distract him with a Digi-Key catalog. Tell him the centerfold this month is excellent or something. Then when he isn't looking, swap your alternator with his.

Howdy Neighbor! I'm in the burbs north of the city. Car looks great! Congrats! I'm no expert, but if you need help, give me a shout. I know some stuff.

Recent discussion on the same issue. Maybe some help in here? http://www.classiczcars.com/forums/electrical-s30/53259-parking-interior-light-fuse-melting.html

Wait a minute... Last I heard, you were driving around with your headlights on and your alternator had failed. Your battery voltage was dropping? "A minute or two later, I was getting 12.8 and slowly dropping. By this time the battery was reading 12.5." When I said that it either works or it doesn't, I meant that there really isn't much else in the whole design that could be an issue with the internally regulated system. Other than a loose drive belt or a bad connection, about the only thing that can go wrong is inside the alternator itself. The only other thing I could come up with is if your CHG lamp is burned out, there's a chance that your alternator won't get itself up over the hump of producing current. But if your CHG lamp works normal, then that shouldn't be the issue. Take it out and have it tested or borrow a known good one if you can and throw it in and see what happens?

Yeah, that sure starts to sound like marketing propaganda aimed at increasing your own sales by torpedoing someone else's product. I used to take my GM to 6000 RPM every once in a while and it never gave me any trouble doing that.

I'll put in a third vote for this. The internally regulated system either works, or it doesn't. You mentioned your charge lamp flashing yesterday... Does it still work today? The CHG lamp should light up when you turn the key to "ON" before you crank the engine. Does it?

Yeah, I grew up on the incandescent as well and completely understand. That whiter than white LED thing just doesn't work for me either. I don't know if it's all mental, or age... But I just don't feel that I can see as well with the cool white shade. The LED bulb I installed is a little whiter than the stock incandescent, but I find the whiter bulb offsets the yellowing old plastic lens of the dome light. End result is that I think it looks like it's "supposed" to look. Original shade, only brighter. Haha! I don't think my hair brained weird stuff I spend my time on is going to scare MSA or any of the other suppliers.