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MG MGB Technical - Rough running / no idle after warm up

79 mgb roadster with twin HIFs and original 45D distributor (manifold vacuum). Was running great except front tappet chest cover was leaking oil. I removed the carbs/heatshield to get at the cover and reseal it (new gasket, high-temp silicon sealant) no leaks now. HOWEVER--
Starts right up without choking and idles at about 750. But, right after the coolant temp needle moves off the peg, idle drops to zip, and rough running with pops and snorts ensues. (Will eventually quit altogether with strong fuel smell and will nto start unless left for hours). Switch off the engine and pop off the air filters, and exhaust is dribbling out of the carb throats.
Throttle linkage and choke linkages are correct and functioning properly, and I didn't mess with anything else.
Any ideas?

Thanks!
Chris Foleen

Sounds like the carburetor floats may be binding, or they could be be filled with gas. Do you know what type fuel pump you have? If a non SU it may have too much pressure.

Clifton
Clifton Gordon

Hi Cliff,

That thought had occurred to me. I installed new floats two years ago during a rebuild. Was hoping I wouldn't have to disassemble but perhaps it's the thing to do.
Chris Foleen

Forgot to answer your other question, Cliff: Fuel pump is stock (probably original) and seems to be functioning properly.

Thanks!
Chris Foleen

This thread was discussed on 21/08/2006

MG MGB Technical index

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