Back Fire - when should it?

When should your early 911 back fire - if at all?

I was in heavy traffic today for about half an hour.......once I got a bit of clear space and hit the flyover and started to acceralte from 2nd to 3rd gear, got quite a loud back fire with a bit of black somke.....is that ok?

thanks
Derek

and then what happened ?

are you running a sport exhaust ?

mfi or carbs ?

I suspect the car understood you wanted to get up and go, so the engine decided it needed to clear it's throat ......

The only time my 911 backfires is when the carbs are not adjusted properly.

standard exhaust. Has MFI.

I too think it wanted to just clear itself ........car was find after this.