Small Block & Big Block Chevy Specific - 1 3/4" headers vs. 1 7/8"

I know this has been argued to death and I'm not asking for opionions or trying to make a decision. I'm just looking for flow numbers or fact for the sake of an argument between me and a friend.

Does anyone know where the numbers are about the headers and about exhaust tube sizes.

He is currently running a small block 350 (old school) he has a somewhat agressive cam (I'm not sure how big but not killer), he is running an edelbrock intake, 750 carb, with 1 3/4 headers and a true dual 2" exhaust all the way back (74 Nova btw).

He is convinced he can add 1 7/8" headers and 3" pipe all the way back and make more power. I'm trying to tell him the expense wont be worth the small if any gain. Can you all point me towards the fact? Or am I the one who is wrong?

I can't point you to the facts, but if he already has 1 3/4 headers, I would leave them alone and put 2 1/2 exhaust all the way back. Esp if it's a street car. He will just be wasting his money with bigger headers.

I agree 1 3/4's are just fine IMO get... i'd do 3 in with an X-pipe and good mufflers.

I picked up 15 rwhp and 25rwt with open 3in/18in collector extentions over my 2.5in duals with h-pipe and two chamber flows.