In this case, the number 48 indicates the carburetor's size. The identification of the jet is scribed on the side. Venturi's for stock 240z's and 260z's. You are looking for a chocolate brown or dark grey for all results. You have worse gas mileage, and the power gain is slight enough to be psychological. Coast to the side of the road and pull the plugs. The piston pushes fuel from its chamber towards the ball valve 21 and towards the ball valve 23 Spill Jet.
Emulsion tubes complete with main jets and air corrector jets 64. Reconnect the two rear plug wires, disconnect, and ground the two front plug wires. In the mileage department, it really depends on the rest of the engine and your driving habits, but 16 to 18 mpg is not unusual on the highway. This produces a lot of overlap that has the effect of scavenging the exhaust gases. This is only a rough draft, which still needs to be edited and checked for errors. I generally discourage the use of anything tighter, like 108, or 106. So, while it may take you three times longer, it's not three times harder.
Triple Weber Induction Systems This article is currently under construction. Consider that you want your average speed over the course to be similar to or slightly below the speed limit. Repeat until no further idle speed increase is observed. The main circuit is the easy one. People brag about horsepower, but torque is what wins races. The pump jet will still deliver fuel at a rate of 0. I didn't know there was a 3rd set to look for when I had the top of the carb off.
Driveability problems can be solved with a little tuning on your own or by relating the symptoms to someone who is knowledgeable enough to help you. You place it over the carb opening and read the air flow. Most of the important components are very similar. Since they were originally intended for racing, they were designed to function beautifully at large throttle openings with only passing attention paid to the rest of the throttle range. Beware of the Internet: but not this page Often many of us go down the path of seeking ideal configuration advice on the internet. First, you must decide your target behavior.
As the throttle valve is opened, it exposes each successive hole to the manifold vacuum and air flow. You will hear a metallic click as the cam is released. Stop when you are at best time for the runs which reflect your desired driving pattern. Replace the pump jet with the next size rich or lean, and then repeat the exercise. The Idle Jet Figure 43. It is simply a variable hole needle valve on the high vacuum downstream side of the throttle valve.
Conversely, a small jet will spray a smaller amount over a longer period of time. In the case of the wrong emulsion tube, there are really only a few that work really. This is the start of my video series on how to jet and tune weber idf carburetors. Remember, we are interested in that instant immediately following the pedal going to the floor. As mentioned above, this circuit actually controls much of the normal driving range, from idle up to 2500 to 3000 rpm. When the accelerator is pressed very slowly, the piston does not offer enough pressure to lift the ball up into the closed position, and all of the gas will flow past the ball back into the bowl. Still others say that ¾ turn is the limit.
However, this never works in practice. Set the idle speed screw at ¼ to ½ turn in after contact with throttle lever. Also if you have used carburetors make sure no one drilled out the jets to a different size. A system with no vacuum advance will require more initial mechanical advance than book values for part-throttle tractability. To reduce variability, use Wide Open Throttle wherever possible, make your runs on level ground, and do multiple runs in both directions. Maybee I'd better leave the buts, and howevers out.
Top End Performance has been your source for the best prices on brand name, top quality car parts since 1984. Now, what we have effectively done is to split the pump volume into two equal paths. Step 6: the actual jets Here is a closeup of the secondary side idle jet and holder. Flow out the idle port itself is further restricted by the idle adjustment screw. Once the correct size choke has been selected for your application, the jetting for all the circuits can be calculated around that choke size. You really have to wind it out to use this one, so be careful! This is done by using a return-style fuel system - the same way that a fuel-injection system does. Its purpose is simply to expel the fuel from the Main Circuit into the air stream.
There is a problem with a purely stoichiometric mixture. Density altitude is dependent both on temperature and air pressure. A lower heat shield and ducting air from the front of the engine bay helps to cool the carbs. So you see, all those numbers and letters really mean something. Disperse the Spray: Drill more holes in the accelerator jet to reduce the large liquid squirt into a finer misting spray. Accelerator Circuit Drawings Figure 24.
So the regulator situated downstream of the fuel loop keeps the pressure in the loop at the setpoint by flowing enough fuel in the return line to keep the pressure bled down. Horsepower peaks at the top end, but torque comes in early and gives you that kick in the pants upon acceleration. Continue to back the screw out ¼ turn at a time until the screw does nothing or runs worse. And while making all that midrange power, what you also have is an engine that revs really fast. They are simply lumps of aluminum composed of a handful of sub-sections circuits that can all add fuel at different times during the operation of a vehicle. So I'm guessing only some of the carbs have 2 idle jets? That, combined with modern fuels designed for return-style fuel injection systems that contain alcohol additives with a resultant low boiling point, leads to a common problem of fuel boilover in Webers. That means that for each carb, the throttle plate is opened precisely the same amount for any given throttle setting.