QuestionHi, first a disclaimer: I'm not a car guy, but I'm trying to learn! I just bought a 1974 (built in Oct, '73) MGB 4 cylinder with a manual choke & dual carbs (not sure if original or ?). At RPMS under 2500 or under a load (eg, going up a hill), the car runs rough (almost feels like it's missing and I feel an occasional soft stutter through the seat) and will backfire through the tailpipe if I push hard on the gas. If I run full choke, the problem goes away and likewise, if I keep the RPMs above 3000 with no choke, it runs better until I hit a hill.
Any thoughts?
Regards, Bruce
AnswerHi Bruce. We all had to start learning at some time. Welcome.
Yes, twin carbs with a choke is original. Sounds to me that the car needs a tune-up.
First, undo the plastic nut on top of each carb and lift the damper out. Look down the hole. Can you see any oil inside? If not, fill the hole to about 10mm below the top with engine oil, and then re-fit the dampers. Go for a drive. Has the problem gone away?
You really need to check the spark plug gaps, the distributor points gap, and the timing. Do you know someone who could demonstrate to you how to do this? If not, find a garage that has someone who is old enough to remember how these things were done 30+ years ago.
Sorry if my reply is a bit vague, but I don't really have enough information to go on.
Get back to me if you think I can be of some more help.
