stock headpipe change only? Dyno?

[98sierraslt4x4]

I know there are 10,000 threads talking about the press bend in the stock head pipe. But I can't find anything about real numbers comparing mendrel bent. Has anyone replaced the stock 1 7/8 head pipe and dynoed before and after to see how much a gain it actually gives? No headers just head pipe with the press bend. That 1 7/8 bend is pressed to 1 5/8s so it's

1 7/8 ID vs 1 5/8 ID= 1/4 inch ID diffence.

 

[GaryCCR]

I seriously doubt it's much. You should watch the engine masters series and the test different exhausts. They beat the heck out of some hookers (headers). Almost no change to dyno numbers. It's on youtube, good way to kill an hour.

 

[98sierraslt4x4]

Yeah I have seen it. That's what makes me really wonder.. You just see lots of people talking about how bad it restricts. But I haven't seen any real number results.