I recently rebuilt a sbc 350 engine. Its just a stock rebuild w/ rebuilt 350 heads, edelbrock intake, & a new edelbrock 600 cfm carb. The problem is that I'm getting a grayish smoke coming out of both tail pipes (it has true dual exhaust). I've adjusted the rockers several times, reset the timing multiple times, adjusted the carb multiple times & I'm still getting smoke out of the pipes. Does anyone have any idea on what my problem could be???