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MG MGB Technical - Still running rich

I have been getting ideas from this list and the email list. I am not sure what step to take next. The car ('73 B minus emissions) has ran rich since it was purchased. So far I have adjusted the timing (10 static), replaced the plugs, wires, cap, and added a pertronix, adjusted the valves, and adjusted the floats. I have also run a compression test on the car. Everything came back okay, but it smokes now after working with the carbs and it still runs rich. I have tried diconnecting the tube for the crankcase ventilation and the car runs a little better but still not that well. Upon replacing plugs the car runs very well until the plugs get fouled. Any other ideas/tests?

thanks
Zach

Zach,
If your cold start enrichment device "O" rings are shot, you will run rich and foul your plugs.
Cheers,
Gary
Gary Cash

I guess i have to ask a stupid question..you never mentioned that you tried balancing and adjusting the mixture screws on the carbs...though probably just forgot to mention..I just finsihed setting up my SU's that I rebuilt yesterday and put her on the road for the season...she runs great! :)

PS I have a 73 too!
Eric

Another thing to note is that the SU carbs often run a little rich when idling at low RPMs. That's why you need to do a good run at higher RPMs, pull over, and then examine the plug colors.

Paul
Paul Tonizzo

Thank you for the responses.

Gary-what 'O' ring are you talking about, I have tried to find it in the book and am not clear as to what you are referring to.

Eric-yep, forgot to mention that I have adjusted the mixture screws.

Paul-upon replacing plugs I took it out and drove it, letting the engine spin up a few times. When I just let it sit, and blip the throttle it smokes black.

thanks again
Zach

Zach,
I've "E" mailed you a page from the Victoria British catalog showing an exploded view of a HIF4 carb.
The "O" ring is item number 45. It took me months to figure out the problem these things caused in my HIF4s.
Good luck.
Cheers,
Gary
Gary Cash

Another thing worth checking if all else fails is the bimetalic temp comp gizmo in the float chamber. Sometimes they get tired and fail. You wont find this until you rebuild the carbs, though.
gerry masterman

As well as the choke O ring failure. If HIF carbs have done more than 70,000 miles they will need new jets & needles. Because the needle is spring biased against the jet they wear badly if the car has had a lot of town running. A look with a magnifying glass at the small chamfer at the top of the jet shows the wear. If the jet has to be raised much above the jet block it usually means thay are worn. After working on the carbs shut the bonnet & run it for 10 mins or go for a decent drive & then reset the mixture as the bimetaliuc strip leans them off when the CARBS get hot not just the motor.
Garth.
Garth Bagnall

This thread was discussed between 04/04/2002 and 06/04/2002

MG MGB Technical index

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