For the 55-57 235 motors the bb is TDC for timing purposes. Now whether it is accurate or not on any given motor is another story. I have had them dead nuts, others a little off, some totally off. So when I am building a 55-57 235/261, I will set the motor up at tdc (which I do with the head off and a piston stop and degree wheel, or if in a pinch you can line up the dots on the cam and crank gears, this is tdc for No. 6, then rotate the motor 180 degrees and that is tdc for no. 1) and then mark the back of the crank flange. Then when I go to install the flywheel, I can look to see where the bb is relative to tdc, and remark the flywheel if need be. Others have a bb but also various markings for setting the timing, a triangle or line for instance where the timing is set some degree in advance (I forget off the top of my headbut that might be 59 or something later) as the timing settings changed from time to time, from application to application, and even depending on whether the car or truck was a Canadian model.
Last edited by Dragsix; 03/01/2018 8:48 PM.
