Update by Tim Suddard to the
Austin-Healey Sprite project car
Nov 7, 2023
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Bugeye Sprite
Early Sprites came with a mechanical fuel pump mounted to the engine. While perfectly adequate for the car’s original 948cc engine, would that setup be equally adequate for our Sprite’s supercharged 1275?
Concerned that the fuel flow would not be consistent enough at higher loads and engine speeds, we followed conventional wisdom and opted to install an electric fuel pump in front of the fuel tank.
We chose a compact inline Airtex pump (part No. E8016S) that makes 3.5-4.5 psi of fuel pressure. The SU carburetor that came mounted to our Moss Motors supercharger requires 1.5-3.5 psi of fuel pressure, so both the pump and the carburetor were designed to run with roughly the same fuel pressure.
With the Airtex pump mounted and wired, we now had fuel at the carburetor. Unfortunately, we had fuel dribbling out of the carb as well. This problem was indicative of two possible issues. First, the float height was most likely not set correctly. To adjust it, we bent the little tab on the float in the carburetor bowl to adjust it to close the chamber sooner.
This helped but did not eliminate the problem. So we got a simple, inexpensive Mr. Gasket fuel pressure regulator (about $50) from Summit Racing.
This regulator fits inline, and we put it just before the carburetor, where we already had a clamp holding the fuel line to the inner fender well.
This mounting location kept the regulator from bouncing around and saved us from having to build a mounting bracket for the regulator. While not the ideal location for visibility, once you set fuel pressure, you seldom change it.
While the pump has a built-in filter, we decided that the safety and convenience of a second filter would be a good idea. We mounted a clear filter right before the carburetor. A clear filter has the added value of showing that fuel is flowing into the carburetor.
The 1275 engine does not have a provision for a mechanical fuel pump in any case. The raised boss where the 948 mechanical pump went is solid and blank. There are lower pressure Facet fuel pumps that would have worked perfectly well without the fuel pressure regulator. As an owner of at least seven Bugeyes over a a 52 year period I have had 948 engines with superchargers, 1275 pumped up to over 100 HP, etc. I have never needed a fuel pump with over 2-3 psi.
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