When i bought this 84 K5, the guy said it was a crate 350, with roller rockers??? anyway, it sputters at times and i get an occassional backfire, but more of a misfire and you can really smell the fumes then. It has a 600 cfm edelbrock carb (which i know sucks, but thats what it has). Maybe the carb is too small. but will that cause it to sputter and misfire??? i have timing light, at idle its alittle above 12. is that good?