emptech

Still waiting for the silicon rubber fuel lines, but in the meantime disconnected the fuel filter and took a container with new fuel, connected to the fuel rail. I made sure to purge the questionable fuel. Cranked the engine, coughed and sputtered and the engine actually started. It was running extremely rough, couldn't even tell if it was all cylinders. Once I cleaned up some spilled fuel on the ground, I'll try again. The fuel level is set to 10 turns (10mm) below the bridge. I then set the nuts on the nozzles to 2.5 turns out from the bridge. I should pull the plugs just to see what they look like, hasn't been running in probably 5-10 years. As the engine ran, I could even hear the electric fuel pump running, thus fuel on the ground. I'm going to connect the fuel system back to kind of normal, where it will suck clean fuel from a gas can, as the tank is dirty. I also need to put some 20 weight or atf in the carbs, think I've used too heavy oil. I didn't have the engine running long enough to experiment with mixtures yet. I'll keep you posted, not out of the woods yet. Jim

I just ordered a pair from Z, I've used silicon rubber hoses before for other gas-related things, they would eventually get soft, but I'm told their's is made for gasoline. I'll do a visual again, looking for vacuum leaks can be difficult, if the engine was running one can use propane that gets sucked up from the leaks and you can hear it in the engine, but this guy won't start yet, oh forgot, need to use new fuel to be supplied directly to the fuel bowls. I'll keep you posted, hopefully getting close. Jim

I'm the original owner of a 72 240z, it's on blocks now, I want to get the 260 out of my hair so I can get back to restoring the 240. I'm all ears, been working on cars for a long time but I've forgotten a lot of stuff, I listen to everyone's suggestions. I've known for a long time the hoses can't be too stiff and normal fuel line is too stiff, that's why I used the special plastic tubing made for model air planes, but as it got older, it got more stuff. I have some chores today, when I get back I'll look into the choke linkage and hoses. BTW, the choke lever broke many years ago and was replaced then, it is a weak point, ever since then I would never pull the lever by the end, always at the base of the lever, couldn't believe how much those levers are selling for. I need to step back and look over the mechanism. Keep up the suggestions - Jim

The fuel lines to the nozzles are kind of stiff. They are a plastic material I bought from a hobby shop, made for model airplane fuel. I bought some su rebuild kits, came with new rubber tube's, did not install them. I made the assumption the fuel rails were the same from flat tops to round tops. I'm wondering if I should pinch off the line returning gas to the tank. The electric fuel pump doesn't get electricity until the engine runs, until the engine runs, residual fuel in the bowls is used to start the car, it works that way on my 72 240z. I believe I swapped out the entire intake manifold, not just the carbs. So the linkages were from a 240z, but we know what assume does. I th8nk the choke linkage may be stiff too.

There are still three fuel rails, one from the filter to the carb bowls. The second one sends excess fuel back to the tank. Nothing to and from the third hard line. I installed a push button switch so I can force the electric fuel pump on. The mechanical pump has been removed and bypassed. While setting float levels I would hold the button down for about 10 seconds while the bows fill, I could also hear gas trickle back into the tank. I have z therapy site glasses on the carbs and when I try to start the engine, the fuel levels in the bowls does not go down, or it doesn't look like it. Is it possible too much fuel is being sent back to the tank?

Now that I have confidence in the float levels, I'm still having a problem getting the engine started. Next step is brand new fuel. A reminder, I removed the 260z flat tops and replaced them with 249z carbs. I read the thread about the nail in the carb, I need to takea step back to see what I missed. Hate to say, the car ran fine with the flat tops, I have to remember, if it's not broke, don't fix it. When I run the engine with a puff of ether, it caughs and sputters, not getting fuel, sounds too lean. I was hoping the bowl level would have fixed it. Somebody had messed with the carbs before I got them. Ideas?

I'm curious as to what the culprit is. Was it the distributor, ignition module? Was it even an electrical problem? I had a problem once with my 72 240z that would stall when going down the freeway. I would start it, it would run again. I ended up putting a Tee fitting in the fuel line from the fuel pump and ran a pressure gage inside the car through the window. Turned out when the engine would quit, there was no fuel pressure. The steel fuel line from the engine to the tank had rust in it. I actually got it cleared by running a wire through the fuel line. So, what happened? Jim

I finally got the fuel level with the jet while turned 10 turns down, I then returned to what people recommend as a starting point, 2.5 turns from the top. With the choke on, will only run on starting fluid. The only thing I haven't tried is fresh fuel, Ive been using fuel I keep for my lawn mower, haven't tried new gas. Ideas? Jim

I think my tab looks too much like a hump, so what happens is the bowl is filled to almost the right level, viewed from the nozzle. I bend the tab down slightly to allow a bit more fuel to flow and it overflows. I think the shape needs to be more of a ramp than a hump, I think what happening, the float gets to almost the right level, I bend the tab down a bit and suddenly the bowl over flows. I think the needle valve goes over the hump. I'm going to try to slightly straighten out the curve. My email is emptech@surewest.net I read it often, don't see this site all the time. Jim

I'm getting very close, one carb at a time. One photo is the view looking down the nozzle, which has been set to 10 turns. Once there is fuel, I can shine a flashlight down the hole and see the level, I'm usually either too high or too low, trying to find that sweet spot. The other photo is the rear float, you can see the weight that was added so when the bowl is at the proper level, the float is level, not canted, where it would hit the ceiling of the bowl. There has been a lot of discussion on that in this thread. One of the photos shows the weights that were fabricated. BTW, although the carbs are from a 240z, they are being installed on a 260z, getting rid of the flat tops. Jim emptech@surewest.net

Mark: I can't tell you how many hours I've spent on these carbs. I bought them used and had no idea how much the person I bought them from messed with them. I've spent many hours trying to get the fuel to the proper level in the bowls. I purchased some sight glasses from Z Therophy so I can actually see the level in the bowls, but I've found that is a waste of time. The best way I've decided is turning the nuts down 10 turns, 10 mm. Taking the domes off and letting the fuel pump fill the bowls, take a look down into the nozzles. I think I'm still about 2mm low, don't know how critical that is. I cannot start the engine. I can start it on ether but can't keep it running, I think it is still too lean. I need to get back to the float adjustment again. If you have been following this thread, I added I believe 6 grams of weight to each float, so when at the proper level, the floats are level, not pressing against the tops. Again, I'll report back. Jim

I decided to go through all 14 pages of this thread. I spent many hours trying to get my fuel level in the bowl correct, whatever "correct" is. I even fabricated a plexiglass model of the fuel bowl so I could actually test the float in combination with the needle valves, which I know are NOT grose valves. I also found I was totally wasting my time by measuring the distance from the top lid of the fuel bowl to the top of the float, which we now believe was meant for grose valves. The critical measurement I've learned is the actual fuel level in the nozzle, not the bowl. Either .426" or 10mm would be the level of fuel below the carburetor bridge. That level happens to be based on the fuel level in the bowl, which is determined by how one bends the tabs on the float itself. Some of us have discovered that to get the proper fuel level, the float is actually too high in the bowl and is dangerously approaching the lid of the float bowl. As you can see, CO has fabricated some brass screws that when inserted into the float will help the float attain the proper angle when the fuel level is correct. I have fabricated similar screws and will drill and tap holes in the float as CO did, and hopefully after re-adjusting the tabs will finally have the proper level. I will report back with my findings, but from I've read from CO, I am expecting good results. Jim

CO, I see the last message in this thread is from Sept 2024. I've spent many,many hours trying to get the float set properly, I've had the same problems all others have had. I've bent the tabs many times and have hit their limits. I'm convinced that adding ballast weight to the floats seems like the best idea. I like the idea of using a brass screw, either off the shelf or fabricated. I have a lathe, so I can fabricate the screws. What did the screws end up weighing? On a '74 260Z I am pulling the flat top carbs and replacing them with 240z carbs. The ears are one long and one short, so appears they came from a 71-72Z. I hope to hear from others - Jim Sacramento, CA. emptech@surewest.net

I couldn't help notice that you were measuring 23mm below the top edge of the bowl. According to the factory manual, the 23mm starts from the bottom of the float bowl lid. Turns out the distance from the bottom of the float bowl lid to the bottom of the lid is exactly 3mm, if you don't count the thickness of the gasket, the proper level for the fuel would then be 20mm below the top edge of the bowl. Nobody has ever said how accurate this has to be, but we know if the level is too high, we get a rich mixture. I re-read your comment, I measured 3.0mm, you measured 3.4mm, close enough. It's so much easier to just measure 20mm down from the edge, why is everybody stuck on 23mm? Jim

Mike: I know you got it fixed, but it seems like a fusible link from your description. Has four pins, if you take the cover off you probably found two wires, each one like an inverted U. One was probably fried. What is more important, what was the cause of the link blowing? A fusible link is nothing more than a piece of wire of a specific gage that gets hot when there is too much current and it burns open, nothing more than a fuse in effect. Jim