exhaust pipe diameter for a mildly modified 340

ir3333 said
I thought a street engine needed some back pressure to keep lo rpm exhaust velocity up for low speed power?
Isn't that why street driven engines benefit from a small cfm carb and why the factory reduced the tail pipes
to 1 7/8" from 2 1/4"? This wouldn't apply for an open header race engine at 6000 rpm.
....but the question is how much power might be lost going from 2 1/4" to 2" exhaust? I'm wondering if there
may even be an improvement below 3500 rpm?

Your minimum pipe size is 2-1/4. Smaller pipes will not improve low end anything.

ir3333 said
I think it does, to a point. High velocity gasses exiting the exhaust will create some vacuum to help pull successive
exhaust pulses out and it also helps fill the next cylinder on the intake stroke.

Correct

Think of an engine that has no exhaust pipe..the fumes would just come out of the valves and blat haphazard against the atmosphere.

Ridiculous

This is why tuned headers only work on long duration cams

100% false

and why exhaust pipes that are too big hurt power.

There is truth in that.

For a street application and small cams this really only helps low speed power.

Not correct

ir3333 said
and will a 320 hp 340 only lose a bit of power above 5000 rpm?

Good question