Spitfire Backfire

[Trevor Triumph]

Driving to Triumphest the Spitfire backfired through the carb. It was under light load- going up a mild grade. One cough and no more. We drove around San Rafael and drove the autocross with no problems. Upon returning to home the car backfired through carb four or five times during the two days- always under light load- not hard acceleration. Elevation does not seem to be a part of it- the first was on I 10 near the California border and other on I 5 and later on I 40 near Flagstaff. Does that sound like a carb, timing, or valve issue?

T.T.

 

[dklawson]

Whenever I have experienced carb backfires, I find it is from the car sitting for an extended period of time and fuel deposits nearly blocking all fuel flow through the jets. I have also experienced this on a non-British car when the fuel filter was almost completely blocked. If your car sat for a while, I would start with simple carb cleaning and new fuel filters. The timing should not be out unless you have recently worked on or with the distributor.