Captain Obvious

Those are the later versions that I've reworked. Yes, those bosses were originally intended for attachment of the small heat shields to the undersides of the carbs, but I repurposed them for the bowl drains. Milled them flat (for a good sealing surface), drilled through, and tapped. I don't think I've ever seen a pair of really early flat tops with my own two beady eyes, but it appears from the documentation that those bosses have been there since the beginning. Here's a snippet from one of the docs where they compare the old and new style float bowl covers. First (early) design on the left, and second (later) design on the right. The first design cover is flat on the outside, while the later design is not flat on the outside because they have the recessed pools for additional fuel. But they all have the heat shield mounting bosses: And about the floats... The float design is very different between first and second designs and I don't think there's any possibility that they are interchangeable. And even if you find you CAN physically mount the wrong design into place, I don't think you want to do that. On the early design, the float mounting ears are on the inside surface of the bowl cover, while on the second design, the float pin goes through the body of the carb itself and is sealed with the brass hex cap. Completely different. Here's a snippet from the docs that shows the differences between the two. New (second design) on the left, first (original design) on the right:

Well I hope everything works out OK. That's no fun at all.

Haha! Bowl drains to help with things like carb adjustments and tuning (things like float level and fuel pump testing) and draining for off-season storage. What I was just doing a couple days ago was replacing the copper washers with nylon because the copper was too hard and it took too much torque to get them to seal. I switched over to nylon for a better seal. Here's a pic of the screws with the previous copper sealing washers: Now with the nylon, dry as a bone at a completely reasonable torque:

If your original issue was the engine cutting off and the tach dropped to zero when it happened, then the main issue isn't (wasn't) the carbs. Someone's got to have good pics of using the clear tube to measure the bowl level. Anybody got a handle on some good pics or videos? I'll ask again for someone out there to loan out a copy of the Just SU's video... Anyone?

Wow. That's no fun. I'm assuming you personally aren't at high risk where you are? Not much to burn in the desert?

Good. Then my work here is done. Here's to hoping those parts found a good new home.

I'm doing this:

That's too general. There are lots of things that could cause a necessity to run four turns down. And now that the floats have been "rough set" using mechanical means, the only way to truly be sure the level is correct is with a clear tube to actually view the bowl level. Everything else is just a guess. I think that would be the best thing... His location is near Naples, FLA. It would be great if there was a kind forum member not too far from there who was willing to stop by and lend a hand!

Haha! I think you did. I could just make a pile of stuff behind her Porsche. She wouldn't be able to get her car out of the garage, but I'd just blame it on you. LOL. Seriously though... I'm headed out of town shortly and have very limited discretionary time between now and when that shed is supposed to disappear. So at this point it's more an availability thing than a storage place thing. I don't think I have time for a parts run.

Call me if you want. I'll put SWMBO on the phone. YOU can ask...

He added the price of $400 to the ad. He also added some pics. It was the "motivated sounding" words in the ad that caught my eye... Words like "Disposing of" and "shed will be removed".

I would change as little as possible and work on one thing at a time. Don't put in any other significant parts (like a new coil) until you have a handle on where you are now. Someone please lend this guy a copy of the just SU video? Any kind member in the Naples, FLA area that can lend a hand?

LOL. Well I'd check it out if I were a 510 owner. Like a 72 510 wagon. Haha! Gold mine. Goose chase. Gold mine. Goose chase.

No affiliation, but thought of your 510 nerds. Could be a gold mine, or a goose chase. "Disposing of a shed full of Datsun 510 parts. Two engines, engine parts, transmissions, struts and other suspension pieces, body parts, Minilite wheels, and more. Bring a truck, make an offer, take it all away. The shed will be removed on Aug 10." https://philadelphia.craigslist.org/pts/d/datsun-510-parts/6654180914.html

Those plated parts look great. I really wish I had a line on someone near me that would do that sort of thing... Fixed price for a bucket. Did you do a lot of pre-plating prep cleanup? Degreasing? Wire wheeling, etc? Also, if that's the worst exhaust valve, you're golden! On some of the engines I've been into, I would have been absolutely thrilled to see something that nice!

Well if that's just a random sample of a valve, then they look great. A quick wipe with the lapping compound and you're done. I don't know the grit coarseness of the two ends of your cup there, but the double ended container I have (green container by Clover) is 120 on the coarse end and 280 on the fine end. I'm no expert, but I tried a bunch of different grits and found that I like something way finer than even the fine side. I ended up with 800 grit. And in my mind... The closer you are to "done" the finer you want. But regardless, they look great for the mileage! So do you have a pic of the worst of the seats?

If the tach is jumping around when the problem is occurring, then the problem is electrical in origin (ignition), and has nothing to do with the carbs. It unfortunately sounds like you may have created some more work for yourself by diving into the carbs. Don't get me wrong though... I wouldn't be surprised at all if there were some gains to be had by working on the carbs, but it sounds like the main problem that got you here looking for help in the first place has nothing to do with the carbs. And, also unfortunately, the carbs are like genies in the bottle. And you've let at least one of them out. Now you've got torn gaskets, misaligned needles, at least one malfunctioning suction piston damper, and unbalanced carbs. I'm so cheery to have around, aren't I? Don't worry. There are lots of people here on the forum who won't rest until you're back on the road. When you get your new gaskets, try to get everything back together and see what happens. Have you ever measured the float bowl level? Did @Bruce Palmer ever get in touch with you to help you with the needle alignment requirements?

Get yourself some 800 grit valve lapping compound and give the valve surfaces a quick refresh? I've used the oil based stuff with great success. And I wouldn't use the Permatex stuff available at all the auto parts stores. Water based, and too coarse. Especially for a simple clean up job.

12-24? Seriously? That's evil. Sure it exists, but nobody ever uses that size! Honestly, I suspect they are really M6-1.0 but there is rust in the threads that make it seem as though the M6 is too big. For the record... M6-1.0 (converted to inches) is .236 x 25.4 TPI And (according to a quick web search) 12-24 has a major diameter of .216 in. So 12-24 would be .216 x 24. So 12-24 (converted to metric) is M5.5 x 1.06 I bet you could run a M6x1.0 tap in there and clean up the threads. Or maybe you could give a M6 x 1.0 bolt a quick hit with a file and knock the crests off the threads and it might fit? I'm certainly not saying it's impossible, but I'm just very skeptical they did that!

LOL!! Can't wait to see you again in Atlanta my friend!!

Using sandpaper to remove even more material from needles that already have unintentional material removed from them probably isn't going to help. To be honest, I'm a little lost on exactly what problem it is that your are chasing... Can you restate the problem you are trying to fix? Maybe a fresh start will help.

Sorry... I wasn't clear. I want to be adopted by this guy: "a buddy has two amazing cnc mills. He owns prototype and design company and also his dad owns a super high end auto build shop."

Adopt me? I require minimal maintenance.

Haha!! I agree. It sure sounds logical at first blush, but I don't believe that it actually holds. Sure would be nice if it worked that way though!

I think riding 1mm higher on the needle will have a significant effect. Much more effect than described above. Easy to test... Hold everything else constant and crank your nozzle up one full turn. I think the mixture change results will be stark. And in contrast... Not so easy to test, but if you were to drop the fuel level in the bowl by 1mm (.039 inches), I think that most people couldn't even tell the difference. Either in mechanical measurement, or in performance of the vehicle.