Captain Obvious

I worry what you would do with such a device.....

Have you tried getting the pin to move using a razor knife next to the float hinge?

Of course the final check should be done with the carbs installed in the engine bay, but they sit pretty much level when attached to the engine. With that in mind, for bench testing you can stand them upright level and use that as a guide. And yes, if they are filling to the top of the window, that's a problem. My first guess would be small piece of debris partially holding the needle valve open a little bit and requiring more than desired force to get it to close shut completely. Other possibilities are the usual suspects. Worn needle,. Rubber tipped needle that has taken a set or has shrunk. Damaged or soaked float. Needle valve spring that has taken a set. etc... You really need to get the float out to diagnose, but I would hate to see you ruin a float to get that pin out. Not proud to admit it, but I've done it. I think if I had more time (at the time) I could have eventually gotten it out without destroying the float, but I was pressed for time. Maybe a little heat on the pin with one of those pinpoint butane torches? I don't remember if I tried that on mine, but it might help?

If you aren't going to run any sort of dashpot, you can trim that tab off.

Neat. Those mirror attachments look like they might be just the ticket for getting down between the two carbs. Do report back. That would be easier (albeit more expensive) than what I do. And once you have a tool like that, I'm sure you can come up with other uses!

Unless the endoscope has a ninety degree head on it, you might not be able to fit it between the two carbs to view the rear sight glass. Would work easy for the front, but might not work for the rear. A little mirror on the end though, could convert to a ninety degree view. Tell ya what... Come to my place and I'll show you how to see the bowl levels in situ! $3.99 at Horror Fright. This and a good flashlight:

Haha! Save your pennies, keep looking, and something will certainly turn up!

Well it's not a guarantee that the car won't start without the air cleaner. However, there are some hose connections (like the thermostatic inlet air valve and the idle compensator) that will present as vacuum leaks if they are not connected to the air cleaner (or otherwise plugged). So if you're running way rich, then having those tubes bleeding air directly into the intake manifolds would actually HELP the engine run. But if everything is tuned properly and you are not running way rich, those unmetered air sources would make steady idle impossible and would probably prevent engine starting. Viewing the float bowl levels is easy with one of those little one inch diameter mirrors (on a telescoping stalk) in one hand and a bright flashlight in the other. Once you figure out how to angle everything, you can check the bowl levels on the car in a matter of seconds. Might be able to do it with a head mounted lamp as well, but I've never tried that.

I think you should stick with buying a car instead of spending so much time posting about a car you don't yet have. Good luck with the hunt!

Pretty good video. Some mistakes on some details and some wrong names for stuff, but nothing harmful. He pulled one of the float pins out with tweezers at about twenty minutes in. That's how the float pins are "supposed" to come out. Hopefully yours will be that easy. My biggest issue is that he spent a whole lot of time dinking around with dry mechanical float measurements... Tang should be some precise distance from the bottom of the float chamber? Rulers and calipers and all that? That's not the important part. What really matters is that the fuel depth is at the correct level in the sight glass. That's why they put in a sight glass in the first place!! Put the float tang wherever it needs to be to get the wet measurement where it belongs. That dry measurement is ballpark only. Get it close dry mechanically. Finalize it wet off the car by pouring gas into the carb. And then confirm final setting in place on the car. He says he was never able to get a view of the bowl level with the carbs on the car? Well, you better be able to figure out a way to do that because at the end of the day, that's the only measurement that matters. All the rest of that dinking around to get things spot on dry is preliminary setting only. Another issue with the whole video is it seemed staged and based on false premise. At the beginning, he's trying unsuccessfully trying to start the car with the air cleaner off. Well no shite.... The car won't start with the air cleaner off. That's probably because he's created some massive vacuum leaks with the air cleaner off. And then at the end, it still won't start because there's a wire off the ignition? Well who's to say that wire wasn't off at the beginning as well? The false premise... My car won't start. I "rebuild" my carbs (without even replacing the float needle valve or bowl gasket or disassembling the power valve to put in new diaphragms). Now my car starts and everything is all better. As proof, here's some shots of me happily tooling around my neighborhood. Don't get me wrong, I'm not really knocking it. I'm happy to see someone actually working on the flat tops and giving them some love. That video could have just as easily been "here's how you take them off and replace them with round tops". Haha!!

It's a little complicated... Kinda depends on semantics. Your recollection that the flat tops are more desirable is completely wrong. The round tops are much more "desirable" than the flat tops. As proof of that, there are clearly waaaaay more people who desire round tops than flat tops. And all of the above is completely true: In 73 they changed to the flat tops. They have garnered a poor reputation. They have been nicknamed "boat anchors". It is not unusual to see round tops where flat tops originally resided. They are more complex and harder to find parts for than the round tops. And it is difficult to find knowledgeable help with the flat tops. Probably the most important parts are the final two points, but the flip side is... You can make them work great if you can find parts and have knowledgeable help. So the summary is that while the round tops are currently way more "desirable" than the flat tops, there is a small but growing contingent of 73 and 74 Z owners who are bucking the trend and are using flat tops on their cars. With great success I might add. Personally, I was into triple digits at least three times last weekend in Z's powered by flat tops. Those flat tops started great cold, idled fine at all temps, pushed you back into the seat at WOT, and got great gas mileage when your right foot wasn't deep into it.

Actually, you have the better set of flat tops there. I wasn't there at the time, but from what I've heard, the earlier versions with the square float chamber covers were a problem and a lot of them were updated by Nissan to the newer version like you already have. However, yes... One of the things that was easier on the earlier versions was getting the float pin out so you can pull the float and remove the needle valve. There isn't a lot of material to grip down in that hole, and my advice is to use carb cleaner and lube on the pin until you can finally pull it out. Narrow tipped pliers is the way to go. Don't mangle the tip of the pin to the point where you can't grab it anymore or you'll have to resort to more dramatic procedures to get it out. Sometimes you can use a razor knife right beside the float hinge to wiggle the pin back and forth a tiny tiny bit, or walk it out a tiny bit at a time. Once they loosen up, they usually come out pretty easy. But if they are varnished in place, they can really be a bear to get started.

And @kats, I don't know if this is the correct setup or not, but I thought of you when I saw this:

I'm home safe. Not caught up yet, but I'm home safe! Special thanks to @GGRIII my traveling partner, and @wal280z my roomie and comic relief while I was there. Thanks guys for having me covered! So the trip down, we had a couple noteworthy events. First, we learned that there is an intermittent connection somewhere in the oil pressure gauge circuit that makes the gauge drop off to zero randomly. Probably the sender unit itself is going bad. Then there was the rain in Asheville where we had to use the wipers that we really didn't want to use. But the most significant event on the way down was the chunk of metal in the tire resulting in a mandatory stop to have a tire patched. We were about twenty miles out from the show and were making our last gas stop when we saw that one of the rear tires was going down. After a couple frantic phone calls and several failed attempts to get input from locals, we found a tire place that pulled the tire and patched us up. The guys at the tire shop were enamored the car, and as it turns out one of the guys working there has a relative (nephew I think?) that is really into Datsun Z's. How much? Well... Picture of a picture, but this much: And for future reference, this is what we pulled out of the tire: The return trip home was more uneventful than the trip down. Other than having no heat (because having a connected heater core is low priority when going to Atlanta, right?), there were really no significant noteworthy events. We stayed in Harrisonburg, VA near JMU and hit a couple local brewpubs in town. But we're back, and I've got a couple more interesting pics that I'll post when I get the chance. It was great seeing old friends, even if they couldn't stay the duration, and meeting new friends! Great to put faces with names! Power to the flat tops!

And I heard from Cliff. He and Mark headed straight to the track from the airport. Looking forward to seeing everyone!!!

There are at least three sets of flat tops at the show. It's a movement!!!

Probably my last visit to the forum before hitting the road. Did a last pre-flight check on the 260 yesterday. Everything looking great. This car has now seen a whole three hundred miles since it was taken off the road over 20 years ago. Hitting the road for a 2000 mile trip. What could possibly go wrong? Out early Tuesday morning and we're staying in Asheville, NC* Tuesday evening and then headed to Atlanta on Weds morning. I'm assuming everyone will be at the judged show and we'll start finding people there! * I've heard there is a nice brewpub or two there.

madkaw, sorry to hear you aren't up to the travel. I wouldn't assume the tune up was a failure though. Might just take some time? bpilati, glad to hear you're making the trip anyway. On final countdown! Bought emergency road beer yesterday. Backup just in case all other options fall through.

I'm not sure that production is really a good idea... I worry that would just encourage people to mess with their AFM's when they probably shouldn't. My AFM came to me already messed with, and the glue blobs completely removed from the inside. Even with bright light, magnification and careful study, I could never determine where my AFM started. My PO removed all traces of the original calibration marks. All I knew was that my car ran very rich, has aftermarket injectors, and my PO messed with everything including the AFM. I had exhausted all other avenues and came to the back-hand conclusion that my PO messed up my AFM. It would certainly have fit his MO. He was after "more power", and I think someone told him that "more fuel makes more power" so he tweaked the AFM. I have since re-tweaked my AFM and it runs waaaaaay better now. So about the tool... I do have a milling machine, but I didn't use it for the gear teeth. I did the teeth on a "shaper". I'm sure you know what that is, but for those who never heard of one, the shaper is the predecessor to the milling machine. Old school. The saying is "You can make anything you want on a shaper. Except money." One tooth at a time and then rotate the workpiece to the next position using an indexing head: Here's a shot of my ancient indexing head. From the late 1800's or very early 1900's: Sorry for the thread-jack!

That tube should make it's way to the engine compartment and connect to your "flow guide valve". It's a predecessor to the carbon canister and is intended to store fuel vapors inside the engine crankcase while the engine isn't running.

What he said. Don't mess with the AFM until you have exhausted all other options. But speaking of such things... I just finished my handy-dandy patent pending AFM adjustment tool. No more risk of SPROING-ing my spring anymore! Looks like this: And here's how it's used. The tip fits in the little hole and the tool gear meshes with the AFM gear and allows controllable adjustment without worrying about losing control. I wasn't there when they calibrated the AFMs at the factory, but I suspect they used something like this:

Well you guys who can't make it will sure be missed. @madkaw So what's the latest with you? How's the spine? Good enough to travel or are you definitely out? Gary and I are planning to get to town sometime maybe late Wednesday morning. Will probably go straight to the judged show (since that's the direction we will be approaching from anyway) and then head to the hotel area after that. And I don't think there was anything nefarious or spy worthy going on here. Or was there...

Well that's too bad about the two of you! @bpilati Brian, what are you gonna do? I'm not officially registered yet as I'm going as a guest, but if there are no provisions for a refund from the committee, I could maybe use your registration and send you some $$ to help recoup the losses? @siteunseen What's the latest with you? Bucket list houseboat trip, or Zcon Atlanta? @240260280 What's the latest with you too? New job still shackling you home, or is there a chance you and your co-pilot could make it?

Good eyes Zed Head. I wasn't even looking for details yet, just big picture stuff. That atmospheric vent on the valve cover will certainly throw off the mixture some, especially at idle. Can't see it in the pic, but I assume the hole on the rubber duct between the AFM and throttle body is capped off. There will be a small amount of air pulled out of the block through the PCV which would be unaccounted for by the AFM.