Hi,
My '72 Valiant s6 still has it's original exhaust system. It swells in diameter just after the manifold connection. What size is it? I need to make a quick open exhaust mod under the drivers floor for the drag strip...Thanks, nico

If it's the 'OEM' pipe then it's 1.88 (1 7/8")... but you say it 'swells' after the manifold, sure it hasn't been replaced? Got a tape measure or a T-square, you should be able to see if it's close or if you're welding a bigger fitting into a 'bend'...

-D.Idiot

Thanks ! it looks like the pipe gets slightly larger just a few inches after the manifold but it could be the bend that makes it seem that way. I think it is original. I took circumference where I want to cut it and at the tail pipe and they are the same! 1-7/8" diameter it is, thanks again!