Tom,
I would think, baring other modifications, that 10-15 horsepower, peak,
is expected. Increase the breathing capacity of the motor with bigger
valves, hotter cam, higher compression, and more cubic inches, and those
headers will add more horsepower, giving them more flow to pass.
The peak horsepower at your "4,500 rpm" range may not be significantly
different, but your horsepower in the peak torque region of 2500 - 3500
rpm will certainly be noticeably higher, which is where you want your
power, anyway.
Steve
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Steve Laifman
Editor - TigersUnited.com
Tom Witt wrote:
> I'm just curious if anyone has ever dyno-ed their Tiger before and after
>ONLY installing headers (and tuning mods relating to the headers - richer
>jets etc.). The reason I ask is that I have a Mopar 318. They did test on a
>360 that was mildly/moderately warmed over with stock 318 manifolds, 340
>HiPo manifolds and various headers up to 5,800 RPM. They did not use
>mufflers, only 24" of pipe off the manifolds. The end results were about a
>10 HP increase with exspensive ($800) TTI headers, and about a 5 HP increase
>with exspensive ($350) 340 HiPo manifolds over stock 318 manifolds! The end
>rating were in the 315HP to 325HP range. I would also think that the
>addition of mufflers would better work to the advantage of the lesser than
>the greater.
> I realize that every model of motor is different much less any
>modifications (cams, heads intake manifolds etc.). Regardless, for all the
>trouble headers seem to be, I wonder on a stock to mild Ford Small Block
>typically driven in the idle to 4,500 RPM range if a significant increase is
>noticable.
> I know that there are header power increases that are often stated by the
>manufacturer, but I don't doubt that the comparision is probably for a
>single exhaust car choked through a single factory muffler. Additionally,
>touring auto museums I often see boat and aircraft engine displays that even
>with attempts to have maximum horsepower still use a cast, log type exhaust
>manifold.
> I'm not trying to get down on anyone who installed headers (you all
>deserve a purple heart for doing so) but rather trying to take a balanced
>look regarding cost, effort perpetual problems and end results.
>Regards, Tom Witt
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