ok ill try and get all info i can to help answer my question..
after running/driving my car whenever i shut it off it back fires, the motor is brand new just built by my local machine shop the carb is new from summit(those street strip carbs its a 650. now the car used to be a carb'd 2.8 and is now a 350.Have a new distributor,plugs,cap,and wires
what could cause the back fire or short continue to run for .02 seconds after the key is shut off?
possibly carb not tuned properly? mechanical fuel pump going? timing off?

any info will be great thanks!

 

Its timing, 9 times out of ten.

 

all right ill give that a try thanks!

 

start with timing. does it have a bigger cam in it? you will probably want to be anywhere between 7-12 degrees BTDC

 

this is the cam in it http://www.summitracing.com/parts/lun-00010lk

 

you need to be at around 12-15 degrees BTDC

 

alright ill give that a shot thanks