Does anyone know what the stock exhaust size is for a 1986 F250 351W C6 automatic? I want to remove my cats since it's emissions exempt and the cats do not even work and are plugged up.

 

2WD or 4WD? 2V or 4V?

 

Most are 2 1/4".

 

it is 2wd 4V

 

Mine was 2.25.

 

It must be since 2 1/4" I accidently bought a 2 inch muffler and it didn't fit, (had to make that one fit lol)

 

Well my applogies...the Parts Catalog contains demensions for many of the mufflers on these trucks...but not for the one in your truck.

But like Dave states...the vast majority of the ones listed are 2 1/4".

Best to just go out and measure it.

 

Yup.

There is no telling what may have been done to it over the course of 3 decades....

 

Well, I can tell that this truck has never had any major exhaust work done to it from behind the cats, only mufflers and tail pipes. The cats and pipes behind the cats look very old.