Thread: 400 small block chevy keeps coughing

Tweet

my 400 chevy small block idles fine and doesnt cough any when you are gentle on the pedal but if you floor it at any speed or rpm it coughs and hesitates and if you have it in park and rev it up it back fires up the carb into the air cleaner. it has a brand new 600 cfm edelbrock carb new fuel filter new fuel pump new gas please help!!!!

and also it wont even spin the tires at all from a dead stop to the floor not even a little squeal

Put a 750 holley on it

Sounds to me like your accelerator pump setting is too lean, assuming you've got it jetted right. Have you gone through the Edelbrock tuning procedures?

Sound like you may have a warn down camshaft lob,that will make it do what your saying.

If it pops once or twice when you floor it, then revs up and runs better, its a lean carb.
If it pops repeatedly at cruising speed when you hold it to the floor, its probably a cam lobe gone.

Retarded ignition and vacuum wrong going to the distr.

are you sure you don't have a square bore carb/spreadbore manifold???? or faulty adapter plates/gaskets?????

did it do it before you put the '' brand new " carb on it ?

Originally Posted by rspears

Sounds to me like your accelerator pump setting is too lean, assuming you've got it jetted right. Have you gone through the Edelbrock tuning procedures?

i have gone through the tuning process before and no luck

May be time to check the base timing, verify your carb connection for the vacuum advance, and if not that pull the rocker covers and look for a flat lobe (minimal rocker action on one rocker).