with the timing light at idle, the crank pully showed 15-16 degrees. and continued past 40 under free rev. the tru times show +4 themselves and each mark on the cam is equal to 2 on the crank so i'm technically advanced like 20 degrees at idle right? how do i turn the tru times back to 0 without taking off the timing belt? and do i have to zero the crank timing before i do so? thanks for all the help guys!!!