Solex 40PI service

[1QuickS]

I just completed a Level 3 remanufacturing effort on a set of Solex 40PI carburetors and wanted to share a few things I learned:

• The throttle shaft wear experienced during low mileage was due mostly to a poorly supported throttle shaft. The shaft was installed in the throttle body and only the aluminum of the throttle body was the bearing support. Since the aluminum easily deformed under closed throttle pulsations it is no wonder that they leaked so soon. I installed oil-filled bronze bushings for the length of each throttle shaft bore, resized the 40mm bores to clean up the ends of the bushings and fitted new butterflies.
• The accelerator pump assembly in each throttle body is a vertically stacked system with the top ball valve assembly pressed into the top of the fuel gallery. The lower ball valve consisted of a ball that seals with a seat that is machined into the throttle body. This makes repair of a leaking valve difficult, especially when access to the lower seat is blocked by a 1.5mm brass cross-pin that must be extracted first.
• The throttle shaft height from the intake of the head for the Solex carbs falls halfway between that of OEM Weber and that of the Weber sitting on a tall intake manifold.
• The auxiliary venturis are similar to those used in the Zeniths in that they are both somewhat taller than the OEM Webers and neither have the main fuel nozzle protruding into the air stream like the Webers do.
• The throttle actuating bars were yellow chromated while the hardware on the throttle bodies were left as silver zinc plate

When I test ran the carbs I used a fuel delivery system other than the OEM design. I ran fuel through a pressure regulator set at 3 1/2 psi and then through an adjustable flow control valve. The fuel lines were split with each one attached to the inlet fuel lines running to the banjo fittings. Fuel was collected from the bottom of the fuel bowls on the manifolds (floats were removed) and then sent back to tank. This is a system racers have adopted to overcome some of the issues with the twin Pierburg pumps. The holes in the banjo bolts had already been enlarged to 1.2mm which was one of the early factory recommendations for these carbs.

I sent the fuel pumps to Ed Fall of Vintage Werks and was extremely satisfied with his personal attention to my particular project, highly recommended!

I attach a couple of pictures; the manifolds and some of the unfinished bracketry are mine and not correctly finished but the throttle bodies are per OEM. The accelerator pump jet components are displayed in their correct orientation, the throttle shaft is shown correctly configured in relation to the throttle body showing the aluminum portions for shaft support just outside of the throttle valve followed by nylon bushings and a very short bronze bearing.