Following the Snetterton ‘non’ race we knew that we had some work to do. The car had not run consistently throughout race day, braking down in qualifying and then running fine before simply stopping altogether on the first lap of the actual race. It clearly wasn’t a problem with the new engine itself but looked like a fuel or electrical problem. We thought that the fuel pump was stopping and starting which could either the pump itself or the wiring to it and so the decision was made to replace both the pump and wiring.
The Facet competition pumps that are commonly used on many carburettor’d race cars are essentially uprated versions of the type of pump that would have been fitted originally and are not without their issues, people tend to use them because they always have done rather than because they are the best bit of kit for the job. They run at higher pressure than is required for Weber carbs, typically around 10-12psi when the needle valve in a Weber requires 3-4psi so it is usual to fit a pressure regulator to bring the pressure down. This however restricts the flow of fuel to the carburettor and this brings you onto the second problem; volume. Carburettors like a high volume of fuel at a relatively low pressure to keep the float level correct, so restricting the amount of fuel getting through is not ideal. We therefore decided to look at other options and settled on an American made Carter rotary pump (we bought two and will be fitting the second to the Grey Whale). These run at 6psi so we still need a regulator (we use an adjustable Filter King) but the restriction is less of an issue as this pump delivers way more volume than a Facet pump and could (given a big enough pipe) empty the MGB’s tank from full in a little over a minute! We also made some modifications to the regulator itself, increasing the inner diameter of the fittings in and out of the unit which gave a much improved flow. In addition we checked all the carb jets were clear and cleaned all the fuel filters.
The other question was the electrical side of things so we removed the dashboard and rewired the ignition and fuel pump circuits, which if you say it quickly doesn’t sound like the massive pain in the arse that it was. Fortunately Marky is much better with auto electrics than Matt but even so it was quite an undertaking but we needed to eliminate anything that could have caused the problems at the last race.
We shall be testing on Wednesday and hope that all will be well!
