on a built 355(400 flywheel hp) how mush increase will i see going from 1 5/8" primary to 1 3/4" primary hooker super comp headers? the exhuast will also be going from true dual 2.25" and flowmaster 3 chamber to 2.5" with a x-pipe and flowmaster 2 chambers at the same time. this is all on a 1971 elky, so no cats?

 

You'd gain some horsepower but lose some torque.

 

c'mon
ttt

 

Do any of you know what that means? An engine is nothing more that an air pump. "If you can't get it out you can't get it in"
Does that make any sense to any of you?
Any time you increase air flow, you increase HP & TQ. The only thing you lose is back pressure. If you don't think so, find and read any dyno tests and try to understand what you are reading.
It may move the output around but you don't lose.
Some of you keep spreading these myths around and never stop to think what you are saying. It's all about combination and tuning.

End of rant,
Good day....
Don>>>

 

i know, i know. i was just looking for some estimates on the power gain. okay?

 

I agree it makes some difference, and technically you do not loose any TQ, but it may move the TQ where you do not want it on the street. In most magazine comparo's between 1 5/8 and 1 3/4 headers on built small blocks the gain is marginal. My car makes about 430 rwhp and I run 1 5/8 headers. I may switch someday but am happy for now.

 

that really isnt true. meaning, if the torque is moved so high up in the rpms you may actually ever get it back. just like an intake, you can move the power band up to a point where you may never actually see it, actually losing power. and actually the collector lenght would play a more important role unless you were right at the edge of power for the 1 5/8 headders. i would look at your hole system first before you mess with the headders.