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MG MGB Technical - #2 cylinder richer than the others

After a 3000 mile rebuild, I have noticed that the #2 plug is darker than the others which are all a nice tan color. I have swapped wires, caps, and plugs to eliminate electrical considerations and use a pertronix igniton system. I'm going to check the valves next but have a question or 2 first (I'll will follow the "rule of nines" procedure by the book). Is it possible my #2 intake valve is opening for a little too long? Would this mean the valve is set a little too tight? Could the exhaust valve also contribute to the richness? I just want to get a clear idea of what to look for before I start. The car runs fine but with a little backfire upon deceleration and I have checked thoroughly for intake and exhaust leaks. Thanks.

Mike King
'69 BGT
Mike King

Mike,

Quite often the #2 and 3 cylinders run a little bit richer than 1 and 4. Normally one should set the mixture correct for 1 and 4 and allow 2 and 3 to be a tad rich, as it's better to be a llittle rich than lean. As far as the backfiring goes on overrun, do you still have the air pump and gulp valve installed? When doing the valve clearances, I would suggest checking the torque on the head studs again, then set valve clearances. If you used new studs and nuts, 3000 miles may have put them through enough heat cycles to stretch them just a bit, affecting the torques settings and valve clearances.
Paul K

This thread was discussed on 16/08/2002

MG MGB Technical index

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