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MG MGB Technical - Odd engine problem

I have an early rubber bumper mgb roadster with a replacement BL Goldseal engine which has done about 5000 miles. The car has a reccurring problem that I would like some advice about. The engine fires up and runs sweetly with decent acceleration for the first few miles/until the engine is hot. Then it begins to miss fire. The missfiring gradually gets worse. Recently if I for example pull up to some traffic lights as i put my foot on the accelerator to pull away the engine stalls and although it turns over will not fire. I have tried replacing the ignition coil and checked the electrics and all seems in order. The carbs have been reconditioned and set up correctly and the timing has been set correctly too. Suggestions please. This is driving me NUTS!
Mark Pollitt

Is there a heat shield between the carbs and engine?
Not familiar with SUs (We got the Zenith in the U.S.), but could be
vaporization in the fuel bowls.

But also try replacing condensor if points ignition, I saw you
replaced the coil already.
Ronald

The heat shield (asbestos I believe) on my '79B was pretty much gone just a little hanging on by a thread.
So I removed it entirely. Does anyone know what type of material is available today that will work in it's place. I am assuming the asbestos is no longer available. If they are still available where can one get one. I would like to replace the one that fell apart with whatever material will work the best.
Thanks,
John
John F

John F,

Moss has a replacement heat shield. It appears to be made of some type of compressed silica or fiber. Kind of pricey, but it works. I put one on my 77 when I rebuilt the engine 2 years ago.
Paul Konkle

Mark, Next time it happens place a wet or damp cloth over and around the float bowls on the carbs. If this cures the problem then fuel vapourisation is most likely the cause.
If not check out any vacuum line or lines allowing air into the tank and fuel system. These can age and collapse causing fuel starvation and also the symptoms you mentioned. Remove the fuel cap and listem for a "sucking" sound when you do if you hear one then a partial vacuum is probably being formed by the fuel pump pumping fuel out and air not being allowed in to replace it. If the problem disappears immediately and occurs again shortly after then this is a possible cause. Cheers, Pete, Sydney, Australia.
(A long, long way from Lancs !)
Peter Thomas

Thanks for your suggestions. I will give them a try and let you know the outcome.
Mark Pollitt

This thread was discussed between 16/01/2002 and 18/01/2002

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