240260280

Good questions young grasshopper! You are correct. In general,carbs work by venturi vacuum (often called depression) lifting fuel from the surface and pulling it into the throat. In the DCOE, the idle circuit, progression circuit and the main circuit all do this. The amount of fuel lifted is proportionate to the fuel level. If it is too low, no fuel will be lifted. If it is too high 100% fuel will be pulled and no air (except what is coming down the throat). Adjusting the fuel level in a DCOE is not a fun job but once it is done it rarely changes. Here are two ways to do it, I recommend the second: On car: 0. remove plugs 1. remove fuel lines to a carb 2. remove screws holding that carb's lid 3. lift lid and bend tab 4. siphon some fuel out of bowl to lower level 5. install lid (often two screws are fine) 6. connect fuel hoses 7. run starter to fill bowl 8. measure fuel level 9. if not at target (27mm) repeat 1 to 9 10. Repeat for all 3 carbs Off car: Get a friend, a ladder, hose, gasoline (water works but gas is more accurate), a clear plastic bowl, and an area with a high roof. Do this: https://www.classiczcars.com/forums/topic/52084-setting-fuel-level-weber-dcoe/ Note: floating the bowl in gas will be more accurate for the level however the 8.5 to 9 foot head of water will give the right pressure on the valve, so gas in the bowl and water in the hose for best results. I just used water and the result was all 3 carbs were the same level. When I put the carbs back on the car and ran the engine, they all measured the same level which I think was ~ my target. Memory is not what it used to be. If you use fuel in the hose, 10.5' of head will give 3.4psi at the carb's needle valve.

Here is a picture of the engine compartment of one of the earliest 240z's. Date would be ~ Aug-Sept 1969. You can see the air filter housing colour is like yours. Spare parts housings were also reported to be delivered in this colour.

Good data. This may be why the WOT run is not flat for all Etubes. Could you please raise the fuel to 27mm down and leave the existing parts in. It will enrich all circuits so be aware. It would be good to see what it does to the WOT shape before dialing back the fuel jets. Hopefully the shape will change.

Jeff, FYI:here is a long thread on optimizing 45DCOE's on an L28. We are getting closer to a final optimized state but there is one unfavourable parameter we have not been able to tune out yet . Hopefully we will get it resolved before you go to triple 45's so that it can help in tuning your application. https://www.classiczcars.com/forums/topic/56375-weber-selection-and-initial-jet-tuning/

Maybe it was to protect the bearing from over torque, i.e. the copper would compress if the torque or a force exceeded the max torque spec. Sort of a sacrificial "bumper".

(dip stick) Or you can stick a wire tie down the main jet tube to the bottom then mark where the top of the bridge is and measure from it to the wet point.

Here is another (optical): Optical_Tool_Turning_Dark.MPG Optical_Tool_Turning_Dark.MPG

Here is another (pipet):

Yes. Here is a quick way to do it:

Before you make any changes. What is your current fuel level? What is troubling is the 3 point range of the WOT runs that we can not remove with E tube change or accelerator circuit. The Venturi size or ratio of venturi to throat (or fuel level) could be part of this seemingly untunable undesirable curve. It needs to be explored further. FYI It looks like the accelerator pump circuit removal leaned the top end out ~ 1 point. The big dip at the first 1/3 of the WOT run is the gorilla in the room. Hopefully fuel level lowering can remove it.

Lovely Thread! I rate it 5 monkeys! ?????

240z needle valve is 2.0mm (below). I can not find data for 260z.

I may have a few kicking around.

If you use 45's then consider a 33 or 34mm choke. The transition from the 33mm choke to the larger 45mm throat (vs 40mm throat) is the challenging tuning aspect to address according to Passini (fuel will precipitate). Below is a table I made to help fit side-draft carbs to Datsun I6 Engines of different displacements and 6500rpm redline. The red trace is for racing applications and is taken from the Weber's formula. The blue line is extrapolated for street. 3 real-world data points are plotted to validate the extrapolation. For an L28 street application, a 40DCOE with 32 or 33 mm choke is the ideal. For 50DCOE racing and running at a 6500 redline, one will need a 3.4litre displacement engine. note for racers: Operating at higher RPM's than 6500 pushes the red line up.

Check the block breather to pcv hose. They go soft and gummy. Your z has the improved AAR hose routing so that is good too. This will get you into trouble: http://atlanticz.ca/zclub/techtips/efisystem/overview.html http://atlanticz.ca/zclub/techtips/electricalconnections/index.html

Love it. I have some 280z parts I can send. I 'm pretty sure I have those elbows to the throttle body.

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Magnesium & Cars: redefining Burnout.

I had light weight magnesium alloy seat rails on my first road bike. They failed 60km into a 120km ride. I did the last half standing on the pedals. a reasonable facsimile

I don't follow anyone.

Vapour line does little. You seem to be running out of fuel in the bowls or have some sort of strange air leak into the manifold that increases with rpms.

Oh boy! You are in for a treat. Torque, Sound, and Superb road feel. You will love it,! After you break it in consider 40mm triple carbs!

Thanks! Brought back memories!

yes it is strange. The poor guy in 2013 had the same problem.

bad design https://www.acxesspring.com/coil-spring-slenderness-ratio.html