How much do headers help a stock hemi?

[dammstrate]

My 66 Coronet Hemi tribute has stock manifolds and 2 1/2" all the way back through some Dynaflows with and an "H" pipe. The 472" Hemi pulled 425 at the wheels, which is probably close to 500 at the crank. So maybe it's a "+1" from a stock Hemi. How much would headers
improve this? Would I even notice?

 

[Imperial One]

See Nick's garage dyno test:

426 HEMI Stroker - Headers VS Manifolds




MOPAR Dyno Battle - Headers Vs Manifolds

 

[Rusty knuckles]

Excellent videos above and very apples to apples for your engine I would think. That was a lot of HP lost. I'd think 3" exhaust would help you a lot too.

 

[Bighouse]

The difference is an entire VW bug.