Where are headers measured?

[jamesjedi]

It is the inside diameter that is measured, but where?.....at the collectors or the pipe that goes to muffler? Should these measurements be the same?

Thanks for the replies
JC

[ttweed]

Actually, many people specify header size by the outside diameter of the primary tubing, including manufacturers like George Narbel of European Racing Headers. If you specify 1-3/4" headers with him, the ID will be 1-3/4" minus twice the wall thickness of the tubing, or approx. 1-5/8".

The secondary tubing, after the collectors, is always larger than the primary tubing.

TT

[jamesjedi]

Perfectly answered...Thanks.