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MG MGB Technical - engine problem

I have just finished a major engine rebuild on my 72 roadster. Re bore, Pistons,Main and Bigend shells, Oil pump. etc. Starts and runs great. Very quiet compared with how it used to be.
Took it out for the first time yesterday and today and its fine apart from it is occasionally coughing back through the carbs, It is not doing it all the time, just now and again when under light acceleration.
I suppose it could be that the engine is tight but wondered if any thing else could be affecting this. Your views would be welcome.
Trev
Trevor Harvey

A bit too advanced?
Art Pearse

Re-check all the settings for carbs and ignition. Maybe run it very slightly rich initially.
J Tait

Could be almost anything. Does the tach flicker with the cough? If so an ignition LT problem is indicated, like points or a bad connection somewhere.

Other than that it could be a valve sticking, HT problem, or almost anything to do with the carbs, points, plugs, timing, distributor etc. etc. I wouldn't expect the tightness of a newly rebuilt engine to be the cause.
P Hunt

My guess is that the timing is slightly retarded and when you accelerate lightly you remove the vacuum from the vacuum advance, which causes the timing to retard further and backfire through the carbs. RAY
rjm RAY

You may have an induction leak at the inlet manifold or carb gaskets. Check this out before going any further.
Iain MacKintosh

This thread was discussed between 02/03/2010 and 04/03/2010

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