Stanley

I didn't like the idea of running hoses from the float bowl vent to the air filters. As long as it's just fumes coming out that's fine but in some cases fuel can come out. Especially bad if you have headers. So I ran some clear yellow Tygon fuel line from both vents to the nozzles of couple of Sriracha bottles taped together where the windshield wiper fluid used to be. The caps with the nozzles need to be loose on the bottles or it won't work. So if there's overflow while driving or adjusting the floats no big deal. I've never gotten more than about 1/2 ounce of gas in the sriracha bottles. If you car has been sitting awhile like mine was until this week it makes it easy to prime the bowls. It's way easier to pour a little gas down the Tygon lines than it is to try to get it down the vents. For the cam cover vent I previously ran a hose from it with the open end between the K&N's. Using an ITB now. Haven't decided about that vent. Hope no bugs go in.

Well, it was OK but not great. There's a few seconds delay between shifting and when it actually shifts. Jerky and wouldn't shift into 3rd at all. So driving 45 in 2nd gear. And the 280zx modulator didn't fit the Jatco 3N71B. Same thread but a little wide. I think the case for the 3-speed AT's changed around 1978. The earlier ones fit the later trans but not the reverse. So ordering another. Hope it doesn't blow out this time.

Thanks. I trust old Nissan parts more than new "globally sourced" parts. My new modulator says made in USA but we'll see.

Yes I'll try it round the block first. Maybe the rabbit or a young malnourished child assembled the two that failed. Yes they were drinking and smoking ATF. Or possibly the bigger engine makes too much vac for the little modulators. I've got one for a 280zx to try next. My jack and jack stands are too short though. Difficult to get under the trans and it's hard to work on so close to the collector so I'm taking it where there's a lift to install the new one. Hurt my shoulder installing the last one. If my arm was a foot longer I could do it easy from the engine bay.

Been a while. Anyway I want to temporarily drive with the vacuum hose to the modulator clamped off. It's a stock 3-speed AT. Engine is modded 280Z. I'm used to shifting manually but concerned by stuff I read. Will it hurt anything? Any tips on driving and shifting without it? Only driving 20 miles or less.

Just be sure the air galley doesn't have any rust holes. If it does then exhaust gasses will enter the cabin.

For the water jar method, will the float sit the same in water as it would in gasoline?

The air galley is the bad one. It can be rusted out and leak like a sieve, gassing you with exhaust fumes. As far as I know they are not available so the only solution is to remove it and block the ports for it on the manifold, or get headers.

My Hitachi AM/FM is gutless, only picks up a few stations, and drifts away from the stations it gets. I'm planning to swap in a new radio but would rather keep it looking stock. So hell yes I'd do that.

The car runs best at correct air/fuel ratio. High altitude has thinner air so a leaner mix is required. High temperature also has thinner air, so leaner mix required. Cold air is dense so richer mix is required. There's a graph in the carb tuning section of the manual that shows altitude and temperature vs initial number of turns down at the mix nuts. So on a hot day in Denver you'd want a lean setting. On a cold day at sea level you'd want a rich setting. Dunno if that affects your issues.

Floats need to sit correctly in the float bowls, otherwise they can stick against the sides of the bowls. Adjusting (bending) the hinge tab and/or a light touch with sandpaper on the float will fix that. If the valve isn't new it could have some gunk in it - fix with carb cleaner. The other answers are also correct.

After installing a modified 280 block with modified 280zx head & stage II cam in my 240Z, my AT modulator promptly blew out and started sucking ATF into the engine. Put a new modulator but it seems to have blown out as well. Maybe the the new engine is making too much vacuum for the flimsy modulators? Trans is 3N71B, stock 3-speed AT for 240Z, 280Z, and 280ZX, Maxima etc. AFAIK. Looked at Rock Auto, they have same (and some different) ones listed for the various models, from $11 to about $50. Two are listed for 280zx as "fully adjustable", one with a 910" diaphragm for non-turbo, and one with a .840 diaphragm for turbo. The same $11 non-adjustable Fram is listed for all years of 240Z, 280Z, and 280ZX, so I guess they're all swappable. I found this, not for a Nissan: "use a small slotted screwdriver to turn the adjuster that is located inside of the vacuum fitting. Turn clockwise for earlier shifting, counterclockwise for later shifting." I guess I need a tough adjustable modulator but guessing and following manufacturer's hype can lead to destruction. I'd like to have an idea what to do before I start "adjusting". Anybody know? Due to the headers it's not real easy to get at the modulator, so would like to get it about right first time.

Whatever the future may bring, I've become more aware of changes in driving habits. Couple weeks ago I was behind a driver who was all over the road. When I was able to pass safely I saw her looking down at her phone. Last fall I was one of the first to stop at an accident where an SUV rolled on it's side and a woman in the other car was trapped inside. We pulled the SUV driver out, she said she was lost and looking a map on the screen. I've been seeing a lot more "failure to yield" in the last few years, when drivers making a left turn cut off approaching cars. I don't know but I suspect they've gotten used to following orders from their navigation systems and just turn when told to. Also, on a recent road trip to Arizona there were a lot of slow big rigs in the right hand lane. Often there would be line of cars in the left lane waiting to pass, and a driver would fly past in the right lane, get behind the truck, and then slip between the left lane cars and pass. So it's 80 mph and only about a car length between cars. One little mistake and it's a tragedy. And on a 6 hour trip they might only save about a minute doing that. I usually ended up passing them later, with the cruise set at 79 mph.

https://www.newyorker.com/culture/annals-of-inquiry/the-fight-for-the-right-to-drive?utm_source=pocket-newtab

After a few minutes of trying to balance a pencil on my finger and thinking about the boundary conditions, I gave up. After all it was beer time. But modeling the system in Matlab was required. I don't own Matlab but it's said to be a very powerful program. Maybe fluency in its use would be a big advantage in solving the problem.