Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Supercharger performance

I refitted my Judson last night, and went for the test drive this morning.

I didn't change any timing settings, just took off the SUs and bolted on the Judson.

The car idles well, and will rev easily, but is not even developing the power of the SUs when under load (uphill for example)

Anyone got any ideas about why this should be, I have 64 jet in the Holley, and it doesn't sound like it is running lean or rich. Tips for getting it to run right would be appreciated - I am hoping to give Jeff Becker and Gary Lock a ride in it in two weeks.

dominic clancy

Dominic, I am trying to think back on the changes you made over the winter--I seem to remember you having the carb rebuilt. The 64 main jet sounds correct but if the economizer valve is not working properly you will not get the additional fuel needed when on boost. Vacuum holds the valve closed under the spring pressure and when the vacuum drops (as the throttle opens) the spring unseats the valve allowing more fuel to flow into the carburetor. Other than that you could have a leak on the intake manifold allowing air to enter without going through the carb.
James Johanski

Do you have a vaccum guage to monitor the engine? That should help you find what the possible source of problem is. I WANT that ride.

Jeff Becker

Hi Guys

There can't be an air leak on the system - if that happens on the intake side, the thing is just uncontrollable and runs away with the revs. This is not happening.

I've the same symptoms with both carbs (I tried fitting my spare Holley as well).

The gauge is showing vacuum but not much in the way of boost. The vanes are new (and making a hell of a racket).

It's making all the right noises (and boy is it louder than the SUs), but it is missing the grunt under load

dominic clancy


I find if I have even the slightest vacuum leak I lose boost

L Caya

This thread was discussed on 14/05/2011

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.