240260280z

For a stock system, the mixture knob should be set for idle a/f only and the needle's taper should be adjusted for a/f ratio at different rpms/load. (adjusting the needle means swapping it, sanding it, or turning a new one on a lathe). In a stock system, the needle taper should already be optimized for a balance of power, emissions and fuel efficiency as per the factory's best effort.

Lifting the piston adds more air as there is not enough venturi effect to pull significant fuel out of the jet. Blocking a carb opening will cause manifold pressure to expand into blocked carb's closed-off area over the bridge however the piston will be down so it will limit fuel flow from reduced pressure above jet. A hose from the top of the fuel bowl to the carb body will also present the same manifold pressure above the fuel pool (equalized) so there will should be no push or pull on the fuel.

Here is a photo I found online. This restored set is in great shape but the nylon has a yellow streak on the top and a yellow tint on the bottom. The paint stripper would remove all the yellow.

I had the same problem with a 510 we had shipped from Colorado to Boston. The 1 mile drop in elevation required carb adjustments before we could hit the road.

I was using a paint stripper to remove paint from 71 240z door strikers and the yellow nylon bumpers came out snow white. The same happened to the deep nylon adjusting nuts in the head light assembly. This should make some of you restorer's happy. Sorry no pics I was working more so than normal.

Damper oil and spring affect how slowly the piston rises and falls when the throttle valve opens and closes. It also stabilizes the piston from "fluttering up and down" caused by pulses into and out of the intake. The conundrum: If the piston rises too slowy, then the mixture into the motor will be richer as the venturi suction on the jet will be greater and more fuel will be sucked through the orfice between the needle and jet. As well, the higher velocity and smaller cross-sectional area should promote better air/fuel mixing. However, the higher suctions pulls the piston upward with more force. If the piston rises too quickly then the fuel presented at the orfice will be greater as the needle will be raised higher however the venturi suction will be less thus pulling less fuel. The lower velocity across the jet and larger cross-sectional area should reduce air/fuel mixing. However, the lower suction pulls the piston with less force. So the conundrum is the unknowns and their interactions to counter each other (venturi suction, orfice size, needle taper, air/fuel mixing, piston motion ). For example, you can over dampen the piston so that it runs richer on acceleration but correct by needle profile to compensate and at the same time, the increased Venturi effect will attempt to counter the over damping. You can also rework the bridge to promote more airflow (venturi) but disrupt air/fuel mixing from turbulence but the increased airflow will pull the piston harder and slow the airflow. This whole mystical mechanism really needs someone with a flowbench and engine dyno to make emperical measurements to get the facts, Until then just stay as close to stock as you can and use the recommended damper oil. Heck I was just looking at the weird bumps in the EFI manifold runners along with the offset injector points and Nissan put them there for a reason.... but why? This gets good ~ 2:20 into it. You can actually see the fuel "fog" and the cone it makes down stream from the needle/jet point.

The "British Method" (picture below) is to lift each piston ~ 1/32"of an inch using the pin then see what happens to the idle. I never had much luck with this on the six cars I tried it on as the front carb would seem to work fine but the rear carb never would, or there was very little discernible change. I now use a hybrid of Norm's method with an O2 wide band sensor "Canadian Method". Norm's method "American Method". Is simply to disable one carb at a time by lifting the piston to disable it. In theory if the carbs are balanced, the engine should stumble the same when the front carb is disabled and when the rear carb is disabled. Norm's method is interesting in that, by lifting a piston, you create a huge "vacuum leak". When you have a wideband in the exhaust, the value goes up around 27 to 29 (from my memory from last test in 2005). You can compare between the two cylinders at idle to balance the jet height. I also do this at 3000rpm to ensure the jets/needles match at higher RPM too. I can't recall what happens when you plug a carb's mouth at idle (stumble or stall) butin theory you can try that as well and the O2 sensor should read the same for both sides and be near Stoch.

You learned a good thing today!

Isle of Jersey or New Jersey?

You can connect the ground wire to any of the mounting bolts.

Some suggestions: Check the cam lobes carefully for wear? Are you running a mechanical pump? If so check it's functioning and the eccentric. Crank the starter with the valve cover off to ensure all holes on oil bar are flowing Check all valve keepers and lash pads to ensure none are loose, missing? It could also be a loose valve seat. Check plugs and pull one wire at a time to see if it affects the sound. You may be able to correlate it with a cylinder using these two plug checks.

Yeah we got an f1-f2 (Juan) hit us directly in 2003 (NS Canada) and it was bad but we dealt with it quickly and all was back to normal in 7 to 10 days. I was looking at the NOAA plot for Irene and did not know what the hype was about... f0-f1 is pretty much just a windy wet day. On TV I saw a lot of reporters without wind socks/foam on their mics to try and enhance the low wind so it is easy to see the press are full of BS makers. Here is a low F2's (Juan) power:

Couple of images to add to the procedure:

Any Weber experts?

Maybe clogged return line is driving your fuel pressur up? Used compressed air to blow out lines back to tank. For some reason you have too much fuel. The only causes are high fuel pressure, wrong size injectors, or EFI system not working. I think you checked all of these?

280zx booster on a 260z

Yup, Even a 280zx will fit. You may have to drill some holes for the larger ones. Here is a big 280zx on an early 240z Before and After: Drill holes Clearance and Fit of Big 280zx booster. Note the 280z booster is smaller.

Not sure about parts that can swap. Whole boosters can swap though.

I had same problem with bccd. Just turn it a few turns one way and test. If the idle decreases too quickly at a stop or if it stays high for longer then turn the otherway. The bccd is under the throttle body and there is either a screw or a nut to turn.

Weird but a great question! I looked around and found confusion on this page but I saved you another $50 http://www.racepages.com/parts/brake_booster/240z.html My guess is that any of them should work. Just do some web research on where the vac line attaches and the spacing of the 4 mounting studs and the push rod length.

Go ~ 60mph for a few minutes, turn off ignition then coast to a stop (careful turning off ignition as your steering may lock, you can turn it back on when engine is dead but not all the way to start) After coasting to a stop, read plug #2 and #5 to see what front carb and back carb are doing.

http://www.classiczcars.com/forums/showthread.php?41940-Quick-and-dirty-SU-Tuning http://www.classiczcars.com/forums/showthread.php?43264-Vintage-SU-Carb-Adjustment

Hi, I am refreshing some carbs and the kit has a mystery washer that I can't figure out where it goes? It is the single aluminum washer in this photo at the bottom.