Re: Choosing the Right Header Primary size
If you are going with the same brand headers there will be no change in HP between 1 3/4 and 1 7/8.
The difference is, when you put your car on dyno you will find the difference, with smaller primaries you will get the higher HP on lower rpm than bigger primaries diameter.
Example, 400 hp on 5000 rpm and 1 3/4 headers, 400 hp on 5300 and 1 7/8 headers.
But if you are planning for more mods then go with bigger primaries