backfire

[model a vickey]

i have a stock 1930 roadster with a rebuilt carb(also have switched carbs from my other model a) and every time after driving,i turn the key off and it backfires(loud).what is the problem.it drives great,idles great.thanks ted

 

[Mike V. Florida]

Mine was timing. I could get out of the car before it would go bang.

 

[model a vickey]

thats my thinking too.is it retarded or advanced.ted

 

[steve s]

When the motor is shut off, the exhaust system starts to cool and sucks air into a system that is then at the right temperature and composition to ignite. Three things contribute: Air comes in thru leaks or cracks in exhaust system/gaskets. Too retarded spark will cause the exhaust system to get too hot. Unburned fuel can accumulate in the exhaust system due to too rich or too lean a fuel mixture or weak ignition spark.

 

[Purdy Swoft]

Steve nailed it exactly on every count.

 

[model a vickey]

thanks,that gives me a place to start!ted