Best be checking the Exhaust Valve margin diameter clearance to that 427 Block bore......not likely you have needed clearance at .600 lift......Edelbrock valve spacing allows a larger exhaust valve with that lift in a 427 bore....Shelby doesn't! Buyer/Installer beware! Your Edelbrocks were a much better choice.....remove the exhaust seats, install smaller seats and smaller valves on the Shelbys and start all over....
Have a nice weekend.....
Just my opinion!
Watch that exhaust valve diameter clearance to your cylinder bore at .600+ lift!
http://www.gessford.com/projects/ima...uto427-P01.jpg
George