Popping on overrun.
 

I just tuned and balanced the carbs (webers) on my 71 2.2. I'm happy with the tuning as the plugs look good and it drives well, except that I get popping/firing in the exhaust on overrun when off the throttle. Is this due the mixture being too rich and how can I determine which cylinder it is?

Any advice would be appreciated

Bump...anyone.

Too lean actually, but not necessarily due to the carb tuning. Either you've got an exhaust leak or intake leak. Check all your flanges/mating surfaces to see if you can find carbon tracking. Paul Abbott advises the same problem sources on his recommended tuning tips

Weber Carbs Technical

(Go to Performance Tuning at the way down bottom of the page)

Thanks for the reply and the link. I'm hopeful it's the tuning, as it was fine before I balanced and tuned (or should that be mis-tuned) them, though it was definitely running richer before. That's a great article. I shall go back through his tuning process and see how I get on.

Thanks again.

Don't be TOO sure it is a tuning issue. I had a very bad afterfiring issue with a very small exhaust leak. Good luck.