Stanley

Can't verify the fuel level like that. You need to pull the tubes 2 or 3 inches more through the wire clips that hold them in place, so you have more slack. Then you can hold them right against the side of the bowl and make a horizontal line on the bowl with a pencil, right in line with the gas in the tube. Then get your micrometer and measure from the bottom of the lid to the line you drew. Write down the millimeters and then do the other one. 25 mm front / 21 mm rear down from the lid is correct. I also want to check mine with the nozzle method. My car is raked up in the front since I removed the smog pump and swapped the stock brass radiator for an aluminum one. Beat-up stock bumper is also replaced with carbon fiber one. I did some measurements and calculations to get the front/rear carb fuel level difference correct with the sightglasses, considering the "gasser" rake and the slope of the parking spot, but I think using the nozzle method with the car on a level spot in the parking lot will give better result. Nice thing about the sightglasses though, you can leave them hooked up temporarily while idling or driving the car, so you can check that the valves are opening and closing correctly.

Another option for the float bowl vents is to connect hoses or plastic tubes to them that direct any overflow to the ground under the car. Nothing to it. Or connect the tubes to catch-cans that have overflows that lead to the ground. I was intentionally running slightly higher than stock fuel levels in the bowls and wanted to be able to monitor any overflow, and have it go to a safer place than the air cleaner. I only caught a few tablespoons of gas per year in the catch-cans. Having them go to the air cleaner might be slightly better for emissions, though.

I see you hooked up the sightglasses. Just bend the plastic hose and hold it vertical right against the side of the float bowl. Get a pencil and draw a horizontal line on the float bowl that lines up with the fuel level. Then do the same with the other carb. Get your micrometer and measure the millimeters from the bottom of the lid (or the top of the bowl plus the gasket) and write it down. Then check the other one and write it down. It should be about 25 mm down for the front one and 21 mm down from the lid for the rear. If it's close then you're ready to fine-tune it with the "nozzle" method. If it's Within 1 mm it's close enough since the fuel level goes up and down that much when the engine is running, as the float valve opens and closes. If you watch the sightglasses carefully with the engine running you can see that happening. Use the nozzle method for the last stage since it's the most accurate. Also with the nozzle method you don't need to think about the fuel in the front bowl being lower than the rear. They should both be the same level in the nozzles. If you check it 10 down in the nozzle and they're both very close to right, then you're done. Don't get carried away getting it perfect. You can get almost perfect, adjust the tang very slightly, and just make it worse. In fact the process can be described as "make it better, make it worse, make it better, call it good". Just make sure you "call it good" after making it better, not after making it worse.

Found it, posted couple years ago. I was wrong it's 4 mm difference not 3. Still not clear how this relates to the 23 mm down from the underside of the lid measurement. Fig. EF-47 in the FSM shows a dimension "H" = 14 to 15 mm, that's almost but not exactly like the measurement of 11.5 to 12.5 mm rear, and 15.5 to 16.5 mm front in the tech bulletin. Fig. EF-47 shows the dimension from the underside of the lid to the tang on the float, while the picture in the bulletin shows it from the lid to the outer surface of the float. No big deal I guess. 0.55 inch = 14 mm 15.5 mm = 0.61 inch 11.5 mm = 0.45 inch So maybe make the plastic 0.61 for the front and 0.45 for the rear. TechnicalSupportBulletin-TS73-10.PDF I still think that method's iffy. Too dependent on fuel pressure and the action of the valve. Maybe the new valves with the skinny pins react different. BTW, the pins in the new valves are kind of wobbly and will stick open if the tang on the float isn't flat enough. Too much curve in the tang is bad. Maybe it's possible to substitute the pin with an old type pin, with the other parts new. Haven't tried, might not work.

Dunno

That's what I thought I remembered from a few years back. Not 2 1/2 turns down. Didn't want to post about it since I wasn't sure and haven't tried that method. I don't know where the fuel level in the bowls will end up. I know there's a Nissan tech. bulletin about float bowl fuel levels but I can't find my digital copy. IIRC it's 22 mm down from inside of lid to fuel level for the rear and 25 mm down for the front, please verify this. Page EF-25 of the '72 FSM says it's 23 mm down (for both carbs) ; the tech bulletin corrects this for the later carbs with different front and rear fuel levels. Hope someone posts that bulletin again or has a link to the original posting. Since there's no way to measure from underside of the lid to fuel level we need to use micrometer to measure from underside of lid to top of the bowl, which is easy to measure to. Using the "same level of fuel in the nozzles" method will get the fuel lever difference between front and rear bowls correct if the car is on a level pavement, but it won't necessarily get the absolute level from the lid correct unless the "10 turns down" has been adjusted to work with revised fuel levels in the tech bulletin. Maybe 2 1/2 turns down is correct for the nozzle method, but if you're wrong fuel level will be way too high and run out the carb and lid vents, so be ready to switch your engine off fast if it does. If you have the sightglasses, it might be better to use that for a ballpark setting, and then use the nozzle method to get them perfect. Since the nozzle method gets the front/rear difference correct, you only need to check the rear carb to verify correct fuel height. Mark's post a minute ago would also be OK for ballpark.

Electronic not points, right ? The Chilton Z car manual covers all the various distributors and has simplified methods for setting them, so it might help. Or not. Or there might be a clue in the '74 FSM. Why did they pick on the poor automatics with those crazy distributors. Put a distributor for a 4-speed and it will run way better, at least mine did.

When you say clockwise I guess you mean clockwise when you look down at it. But the mix nut is underneath the carb. It's like any normal fastener. When you screw it clockwise it tightens (moves the nozzle up), counterclockwise it loosens (moves the nozzle down). So 2 1/2 turns counterclockwise is 2 1/2 turns down. You need to get the terminology right because if you follow the tune-up procedure in the FSM (which is the best method in my opinion, and the easiest to follow if you're not an expert since it's written out correctly step-by-step), that's the terminology they use. Think of it as if you're looking at the carb from underneath. I agree 100% with the previous post, BTW.

It just means they haven't been cleaned in a long time. They should probably be cleaned every year or two. Hit them with a couple good blasts of carb cleaner, wipe them off with a shop towel, and then give them one more blast. Same with the inside of the domes. Don't drop them or get them dirty before reinstalling. Don't set them down so the needle could get bent. It's a good idea to wear a gloves, goggles, and P-95 mask when you're using carb cleaner. When you're done setting the floats and tuning the carbs maybe blast the linkage with carb cleaner and finish with some lithium spray grease.

Yes, use the long valve in the front bowl and put the float back in the original holes like Nissan intended. The fuel level needs to be lower in the front bowl and that makes it easy. What happened with the ztherapy plastic sightglasses in the first post ? That's what I use. Or the ones by Randalla. Or use the "both nozzles at same height, same fuel level in the nozzle" method. If you can use either of those methods why bother measuring .55 inch or whatever ? That method is a little iffy, even if it's in the FSM. Make sure the car's sitting level, not on a sloping driveway while setting the floats.

I have no idea why your mechanic does what he does. I take one precaution: drain some of the gas out of the bowls before removing the lids. They need to be turned to easily lift them out and its easier with some of the gas removed. That lets the floats hang down so it's easier to turn the lids. Also, someone recommended using longer hoses from the banjo bolt to fuel rail while setting the floats. Then you don't have to remove the hoses each time you remove the lids, so it speeds up the process. Regarding 2.5 turns down: it's just a starting point. In fact it's only the starting point if the location altitude and temperature vs. mix setting graph in the FSM says so. Here are a few of the things that affect carb performance. If any of these are not stock then adjustments will probably need to be made. Fuel pressure, air cleaner, exhaust system, engine displacement, cam, cylinder head flow/compression ratio, carb needles, carb springs.

Yeah probably. Maybe it was just its time. It has the spacer. Hope it doesn't have anything to do with the new engine, don't see how it could. Gotta get that car to the carwash.

Two hours isn't enough. It can be an all day job unless you're lucky and get them both right the first few tries. I don't think that method is the most accurate anyway. If your tang adjustment is off by 1/32" it's going to be wrong. Make the smallest possible adjustments and test with sightglass or by seeing fuel levels in the nozzles each time.

Almost 2 weeks ago drove my car home from the shop with the new engine. Fuel pressure was a little low, about 3.8 psi instead of usual 3.9. Mix was way rich so leaned it out a quarter turn. Next day went for groceries. It was running OK. Saw the fuel pressure gauge reading wobble, then drop to zero. Drove a couple more blocks and ran out of gas. Next day ordered a Delphi MF039 mechanical F.P. on amazon. Review said it's original type, not stamped metal. Then I saw a cheaper one, a GMB 550-8040, on ebay from a local shipper. Bought it since it would get here sooner. I figured since it was so cheap I'd get another one so maybe I could use the parts to rebuild my Kyosan Denki or the old Nikki. They all got here last week, had to work so didn't look at them until yesterday. The GMB's both came in boxes that showed stamped metal F.P.'s but they were the original type. Delphi was the same. The Delphi has yellow zinc plated screws, so I was going to try that one since I like yellow zinc. But lever didn't feel like there was any resistance, like maybe it wasn't doing anything or hadn't been lubricated, so I selected a GMB to install. All three had the same little defect in the casting that shows the cast parts are all from the same mold. All made in Korea. The Delphi had an odd chunk of metal stuck to the side so I guess quality control isn't too picky. So today I pull the old F.P. off and guess what ? The lever arm was broken just outboard of where the spring attaches. Both sides of the "U" were broken up to the part that connects them. It's a rebuilt Kyosan Denki that I bought at autozone about 2010. Wonder what happened to make it break like that.

It's been said before, but Nissan changed the later SU's, with longer ears for the float pin and a longer float valve in the front carb to make it easier to get the fuel level lower in the front bowl than the rear. It needs to be like that to get the same fuel level in both nozzles, due to tilt of the engine. Otherwise the front float has to be bent to get the same effect. Not good since a float that sits crooked is more apt to stick against the side of the bowl. A correct adjustment can still be made on the earlier carbs I expect, maybe a little more difficult. If you have the later carbs with the long ears on the front one, and drill them to get them the same as the rear, you're slipping into darkness. Maybe the sightglass, or the "same fuel level in the nozzles" methods are the easiest and most reliable. The Ztherapy video also mentions putting a washer under the valve. For fine tuning maybe the valve could be loosened or tightened slightly. If there's a way to install a captive screw on the tang to move it relative to the float, that would make adjustment easier. A tiny change in the tang position makes a larger change in fuel level. At least when it's about right the job is done. Until you decide to mess with it again.

Sometimes they leak

I use 30 wt. but FSM says use 10W-30. There was a discussion about where the oil goes and why. It eventually goes so main thing is fill it to the upper ring before it gets to the lower ring. I tried an experiment that seemed to show that the level of oil affected the pressure need to push up the piston. If it' not done carefully checking the level will make it go down. IIRC the SU tuning manual says if the carb is big for the motor use lighter springs; if carb is too small for the motor use heavier springs. Is it true that some racers run without springs ? Hope not, cause that might confuse the issue.

Maybe, but according to the official SU publications, just putting K&N's instead of stock air cleaner, or a bigger exhaust pipe will require modified or different needles. 280 is 20% more displacement. We've got the mix nuts set 4 turns down already just to keep from going lean at 2500 rpm, and it's making it too rich at idle. I assume the engine builder knows what he's doing, so I'm following his recommendations for A/F ratio etc. to the letter. I think in theory you are correct when the engine is at steady state. But without accelerating you won't go anywhere. If you drive like a kid who sees a cop in the rear view then maybe. I wish 0.095 Hitachi SU needles were available in various richer or leaner configurations for modified engines like the 0.099 European SU needles are. But then we wouldn't need to be as creative. Look at the needles they have to use for 300 HP L-series engines. Mine isn't stage 4 (and I'm glad) but it's got a big cam, headers etc. I did find a defect today. The front carb piston was harder to push up than the rear. Also, the front carb had to be set richer than the rear to run "right". I swapped the plungers which made the rear harder. We tested it with another plunger from a freshly rebuilt set of SU's, that one was stiff too, so I'm assuming that hard is correct and there's something wrong with the "easy" one. Fortunately I have an extra set of NOS plungers so I'm going to swap them in tomorrow.

We've been doing some other stuff for the car so took my first test drive yesterday. New stage II engine. Carbs same as before, N-27 needles modified for richer mid-range and top end, and red SU springs (slightly stiffer than stock), as was required to get the 240 running right with Y70 head, 2 1/4 inch pipe and K&N's. Idle set at 1500 rpm in Park, drops to 700 in gear (to low for cam). AF ratio is abut 13.5 at 2000-2500 rpm which is per engine builder's spec, but drops to 11.5 (smoky) at idle. The engine's not broken in enough to try top end yet. I'm going to try FSM tune procedure today but doubt if adjusting the mix nuts will do the job. Worth a try before modifying anything though. Easy enough to take a little off the needles at the midrange stations. As per SU documentation posted in an earlier thread, if you reduce the section at idle, stations 1 and 2, it will richen the whole needle since the taper needs to be even through the length of the needle. My thinking is to take a little more off midrange and top end, and raise the mix nuts to get a cleaner burn at idle. Also thinking about changing to the yellow springs, one step stiffer than red springs. Maybe they'll keep the pistons down a bit more at idle, keeping it leaner. The bigger engine should make plenty of vacuum to get the pistons where they need to be at high rpm. Obviously I'm guessing at some things here. So, any ideas ? Not used to all the low-end torque. It's like a wild horse that wants to run. Gotta be extra careful with the right foot. Thanks Chickenman for the Zeitronics recommendation.

I'm using Tygon transparent yellow tubing from McMaster-Carr. Been on five years and still OK. They have a chart so you can check if various types are OK with coolant or whatever.

How'd you get the cam cover looking like that? A quick look at that CCV book told me I don't understand the system as well as I thought.

Not the question you asked but I see you have the stock (hot=closed) manifold heater thermostat attached to the front intake manifold. On the stock 240z that thermostat goes on the back of the rear intake manifold to a steel tube that goes around the back of the motor to heater Y-pipe. There's a BSPT hose barb that goes on the front. I think it's a different size hose barb than the one on the thermostat housing so it takes a special hose. All that stuff was available last time I looked. Maybe it wouldn't make any difference where the thermostat is attached (I don't know enough about how it works to say), except the special hose might not fit as well.

I saw the SEM, it's phosphoric acid. It's what my Dad recommended some years ago. I think the lines are more discolored than rusty, hope so anyway. There's also zinc-rich paint. I've never used it, but the building dept. says to use it on welds exposed to the weather after inspecton. But in that case it's going on fresh weld metal, not old discolored galvanized brake lines.

The engine bay brake and fuel / vapor lines are galvanized steel right ? I'm thinking of treating them with Ospho phosphoric acid and then painting them with a small brush. I think I read somewhere you're not supposed to ospho galvanized steel but maybe that only applies to new or un-rusted parts.

Merry Christmas from the South Bay ! Drive careful.