Setting the butterflies in the throttle body - Solex 40PII Carburetors
When you receive your throttle bodies, included is a selection of shims for setting the shafts and butterflies properly. These shims are 0.1, 0.2, 0.3, and 0.5mm, two of each. special note, we have now started adding some of these shims to the shaft and synchronizing the butterflies. You will still have to follow the procedure for adding your end hardware and checking the airflow after final assembly.
We are including the installation of shaft hardware when supplied with throttle body restoration. If it has not been supplied and you are setting up your own carburetors, please follow these instructions. A copy will be included with your throttle bodies.
This procedure requires the use of the end of shaft hardware in your possession. We have found each set of hardware is a little different from the next, so this can only be done with your carburetor’s unique parts. First, mount hardware, with one of the shims, on the end of the shaft pointing towards the front of the car. Check for binding.
Open the butterflies slightly to check the clearance, then close tightly. Now loosen the butterfly screws, keeping the butterflies closed in the bore (they will slide out of place if not careful). Install a shim on the opposite end under your throttle arm and nut. We like to shoot for setting the shaft end play at 0.1mm on each end. Check this again with the butterflies open in the bore, moving the shaft back and forth. You are looking for 0.15 - 0.2mm total clearance. Proper end play will prevent the butterflies from gouging the body again. It might be necessary to repeat procedure between ends until you get the right combination of shims. There should be no binding once all is tightened. If there is any, loosen the hardware and install a smaller shim, as needed. Yes, it takes a long time to get it done right, even by the “experts”!
Then, check to make sure your butterflies are sitting properly in the bore. Tighten the screws holding the butterflies in place. Hold the carburetor up to the light, looking down the bore. There should be minimal light leakage around the edge of the butterfly, as they are cut slightly smaller (about 0.03-0.04mm) than the bore. If you see too large a gap, you will have to loosen the butterfly screws again, turn the butterfly in the bore slightly left or right, closing that gap. Tighten screws and check with the light down the bore again. If you get this right, you won’t need a flow bench to check air volume of each throat. Be patient, its important for the smooth operation of your carburetor. Try to do your best, it can be frustrating to get everything aligned properly!
As a final check, to simulate engine temperature, put the carbs in an oven at 200 F, then check the shaft movement and butterfly fit. If there is binding, go back and check what is causing the problem.
If all is well, and you are satisfied with the way the butterflies are sitting in the bore, one at a time, remove the butterfly screws, and secure them with blue or red locktite. Make sure you use enough, if they fall out, it will go right into the combustion chamber. As an extra precaution in our restorations, the ends of the screws are peened over. This is done with a piece of metal under the shaft screws, then taking a long screwdriver and pounding the screw end. You will see the end of the brass screw open up just enough to make it difficult for them to fall (or be taken) out.