Mikuni HSR Carb for Moss Blower Kit

I love superchargers.  MG has a long tradition of supercharging their cars.  Moss built a wonderful blower kit using a modern Eaton blower.  This is all great!  However, to make things idiot-proof, Moss opted to go with an SU HIF44 carb.  I have worked on 3 different Moss blower installations and it is clear that the SU is the limiting factor in this installation. We even took the G-Ster up and ran it on a chassis dyno.  Power went up great, then flattened out.  The revs would slowly climb, but it was clear that the engine was out of air. Not only that, but hooking up a wideband O2 sensor showed us that the SU was leaning out under hard acceleration, which is a very bad thing with a blown engine.

We came up with the idea of adapting a Mikuni HSR to the blower and are quite pleased with the results.  With vastly more air flow than the HIF44 SU supplied in the Moss supercharger kit, the HSR 48 Mikuni was originally designed as an upgrade for Harley-Davidson motorcycles.  It features a profiled needle, like an SU, and Tuneable jets, like a sidedraft Weber, so tuning is very straightforward.  It also features an accelerator pump, which makes a huge difference with the blower. 

Unfortunately, the pump is too small for use on the MG engine, so I modify the fuel bowl to offer up a larger pump shot.  The advantage is much for flow capacity to keep on going after the SU would run out of air.  The drawback is that you need to drive it like a motorcycle.  Stomping the pedal to the floor under load will kill the vacuum signal, so you must roll into the power as you need it. Slower pedal = car going faster!

Bradley Restoration

Andrew Bradley, Proprietor

14093 Riverbend Rd.

Mount Vernon, WA 98273

(360) 848-6279