Stock manifolds vs. HP manifolds, vs. headers.

[TruckDriver]

How much more horse power do the HP manifolds give you over the stock manifolds?

And, how much more horse power do headers give you over the HP manifolds?

[firefighter3931]

DCG ; Depends on the combo. Headers on a stock engine are usually worth 25hp. The more power it makes, the more it needs to breathe (exhale). Stock manifolds are poor, HP's much better and headers sized appropriately are the best.

Ron

[Chryco Psycho]

 I agree , , I have seen similar engine builds make up to 40 RWHP using headers over HP manifolds 

[charger01]

440 + headers  = major headaches............go hp manifolds

[Charger_Croatia]

After some thinking I would go with HP manifodls on my 400.
Ken (cudaken) got one pair of 74 HP for me and he has conversation with Ron regarding that issue. They both agreed that for mild 400 motor HP manifolds would work fine and no headaches.
As I understood if you go with 400+ horses on motor than headers would justify investment.

[TruckDriver]

After some thinking I would go with HP manifodls on my 400.
Ken (cudaken) got one pair of 74 HP for me and he has conversation with Ron regarding that issue. They both agreed that for mild 400 motor HP manifolds would work fine and no headaches.
As I understood if you go with 400+ horses on motor than headers would justify investment.

That was more less the answer I was looking for. I would like to get between 400 & 500 hp out of mine.