1 7/8 LT's Size difference???
 

I realize there should be an 1/8 inch difference between the size of 1 3/4 VS 1 7/8 pipe for exhaust headers.

But how is the pipe measured - inside diameter or outside diameter?

In other words is it 1 7/8 on the inside or 1 7/8 on the outside?

When I measure the hole in the flange should it measure 1 7/8 or less than 1 7/8?

Obviously if the measurement is outside diameter then the exhaust holes in the flanges will be less then 1 7/8 since the tube is welded inside of the holes in the flange.