Bill. Thanks for the quick reply. The Circle is on one side, there are 3 straight lines, and then a triangle on the other. Assuming the circle is all that matters, how do I tell when the number one cylinder is at top dead center? As nearly as I can tell from the numbers on the motor, the engine was built in 1961, and was originally installed in a series 3100 pickup. But, I don't think that makes any difference. Allen
