1 5/8 vs. 13/4 primaries headers

[shurur]

never seen that anywhere in this thread, but ill take your word for it.

It's sprinkled in amongst discussions in the terminator and newedge threads.

Also supposedly even the NA 3.7" BB blocks need 1-7/8" headers (per NASVT)
EDIT: may have been 1-3/4" headers..can't find my source...
But I'd like to see a dynos proving that as well.

 

[GodStang]

Over the years with the right build I have seen decent gains with 1-3/4" over 1-5/8" and have seen gains with 1-7/8" over the other two. Both dyno and track numbers. You will also get peeps that say I upgraded and lock 300 hp so who knows.

 

[TRQJUNKIE]

once up to a certain power level and depending on the forced induction you have is when the 5/8 vs the 7/8's come into play. your average twinscrew 600 hp car is fine with 5/8 but when you get up in the 800 range with turbo and centri you need bigger. if not you will create the term choking aka starving the motor. this is what is happening to me at the moment. 1 5/8s and 2.5 is killin my centri built motor setup. many threads on certain mustang forums via google search has proved to gain 20-40 ish hp when making the big exhaust switch, again depending the setup.

Are you saying typically gains are between 20-40rwhp when switching from an exhaust setup similar to yours over to a 1 7/8 header and 3" the whole way back?

That just seems a little high of a number unless additional boost was added.

 

[evolve]

I've seen a ~25rwhp gain from going from 2.5" to 3" x pipe and catback. I wish I could recall where, but the guy was using 110 octane (with a big whipple) and simply swapped his x pipe and CB and threw it on the rollers. Conditions were very similar that day and it was on the same dyno.

 

[GodStang]

I've seen a ~25rwhp gain from going from 2.5" to 3" x pipe and catback. I wish I could recall where, but the guy was using 110 octane (with a big whipple) and simply swapped his x pipe and CB and threw it on the rollers. Conditions were very similar that day and it was on the same dyno.

Seen similar gains plus nice gains at the track

 

[TRQJUNKIE]

Very well

 

[broke7]

My car made 744whp on a 2.8H thru some 1-5/8th MAC's, 2.5" Xpipe and Bullets.


Here is something scary. I ditched the MAC's for my new build, before I sold them I measured the ID of the header collector and it was about 2.25-2.3" in most place. Not anywhere close to the 2.5" X-Pipe. After seeing that mess im pretty sure there is some power to be had which I will see with my new motor.

The quickest twin screw combo in the land for 03/04's is using ARH 1-3/4 x 3" if that tells you anything. If these cars were choked out by "small" exhaust you would see it exploited way sooner. Then again I can remember making 690whp on my stock manifolds.

 

[JrSVT]

It really all comes down to what your pocket book can handle. Will the 1 5/8" primaries give you gains over the stock manifolds - yes...will the 1 3/4" primaries give more gains over the 1 5/8" primaries - yes... Obviously there is power to be had elsewhere and most people have already done those upgrades (ie bigger blower). If you have a bigger blower and are pushing it into it's sweet spot then yes the larger headers will net a little more power.


Jr.