> So, when the crank mark is at 5'oclock on the oil pump mark and lined up, is > that alway 0 degrees BTDC? Not always. If you have the top timing cover off and turn the crank you will see that on one revolution both the top timing gears will be at 12 o'clock when the crank mark is at 5 o'clock or 0 degrees. The next time around they will not be at 12 o'clock. Paul