hi guy's recently rebuilt my buddys 440. basic rebuild with ported 516s 509 cam etc... we got it all together went to fire it off for cam break in and it runs for bout 5mins and dies like someone turn the switch off. wont restart unles it sits for a few mins. any ideas changed coil carb is good n cool full of fuel 7psi fuel pressure. could the msd be takin a dump?