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MG MGB GT V8 Factory Originals Technical - tuning a MGB Moss supercharger

I fit a Moss supercharger kit on my MG B GT 1972, which have a normal compression motor.
But I find the motor is not powerful, I doesn't succeed to start with the choke, and I must depress the accelerator pedal to start the motor. The motor seems to be less powerfull than before and it turn not smooth, but on three or two cylinders at beginning and it must be hot very hot to turn normally. I thought it was the time advance, but when turning the distributor, it has no effect. I don't know how to tune-up this supercharger...
Can you help me?

Christian Delaval

If you go back to the Subject you will find a "Supercharging" topic near the bottom of the page. Probably good information and knowledgeable people there.

Good luck,
Edd Weninger

what is AFR test? the advance must be 5 before, isn't it? how to tune carb mixture? I didn't modify valves, you think I must change valve clearance? before the advance was 13 ) before. I didn't change it before start the motor and after I tried to change manually, but without better result. Before mount SC, the motor was great, a super good compression and very good combustion because I put a ignitor with hall effect. I fit the SC in following the guide, and when I started the motor it start but not with the choke, but with accelerator. the motor run but very rough, on 2 or 3 cylinders at cold and after run normally but not very powerful. When I depress the throttle pedal, I hear a big "shuffle", but the motor is not power, very powerless than before....
Perhaps the serpentine belt is not enough tied? But I doesn't think.
Can you tell me to tune the carb mixture?
But it is not normal that the ignition is bad, because before it was very good....
Christian Delaval

AFR - Air Fuel Ratio
Tony Bates

Christian- Are you getting any useable help? Vic
vem myers

but Do you think my problems with Moss supercharger for MG B GT 1972 come from the fact I put 95 unleaded fuel and not 98 unleaded fuel in my MG ? That is to say bad power, run on 2 or 3 cylinders, difficulties to start with choke?

Christian Delaval

When you run a supercharger, your ignition system has to be A-1. But from your description, I am inclined to believe that you have some crossed plug wires.

Octane should not have an effect on startup and idle.

Wayne Pearson

Hello everybody,
I'm very happy because my supercharged Mg b Gt run good. Effectively, the problems of bad power and misfire was due to bad mount of supercharger manifold and leak with gasket. I made up some stepped washers to deal with the different thicknesses between the inlet and exhaust manifolds and after I started up the motor and.....nothing, just an explosion on one cylinders.....I changed the distributor, verify the advance timing, the carburetor, all was good. Finally, I put the old spark plugs and oh happiness, the motor started well and I made test on road, all is good. It is vey special that the spark plugs of the kit were not good.

Christian Delaval

Christian- Can you flesh out the complaint over the NGK sparkplugs, please. This first I've heard of this one. RegaRDS, vEM

vem myers

This thread was discussed between 02/06/2007 and 15/06/2007

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