I have a mustang with 289 just dropped a 4 barrel 600cfm Edelbrock preformer carb in it, after shutting it off the engine diesels. I pulled off the air cleaner and found out that when the engine turns off gas sprays out the carb! Any help appreciated.
"Dieseling" or after run can be caused by numerous things. Among them are idle speed too high, mixture too lean, timing retarded, engine temperature too high, fuel octane too low for engine or wrong heat range plugs installed. If you have had the heads rebuilt, the valves may be too thin or the compression too high which can be caused by carbon buildup in the cylinders or build specs. It is normal to have some back spray when this occurs as the ingnition is not controlled in any way resulting in pressure in the intake. The back spray is not of itself an indication of a carb problem. It has been my experience that the Edelbrock and other derivatives of the old Carter AFB design tend to run a bit leaner than other designs and must be properly calibrated. Overall, IMHO, this is a more efficient design for a daily driver vehicle with better reliability than some others and tends to "stay in tune" better once you get it there.
Check your timing. The gas spraying out could be from the intake valves being open when the compression stroke starts.
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