I am going to change the header and exhaust on my D16. I was thinking of doing a powercore header which would have a two and a quarter inch collector. I am going to have my exhast custom piped, with most likely a magna flow muffler. I was thinking that it would be logicall to have the piping in two and a quarter inch piping to keep the exhast flow velocity higher. Is there any reason to have the piping two and a half? Please let me know what other characteristics to look for and what you think the best way to go about the header and exhast set up is for this application.

 

ttt

 

I would say that for the horsepower output for that particular engine you have no need for the larger diameter piping. 2.25" will be plenty, just make sure you get a 2.25" cat as well so that the exhaust flow has a straight and even path.

2.5" would be over kill and 2" would be restrictive. Let us know how it turns out.