OHSIXX

Second question: Is a 3 percent hp gain reasonable with headers?

Corey_68

The noise will increase some because you are push more air out. I find the tone is usually deeper.

BSeery

yes, and I hope changing to headers and duals from my factory restrictive manifolds and wonderfull 2 into 1 system will give me more than 3% HP increase.

It better for the $1000 I have invested in the exhaust alone.

vettfixr

Yes headers do change the exhaust tone especially under throttle. I think the tone tends to be deeper. You will also hear a difference because of the material used in the header vs cast iron manifolds. Cast iron manifolds tend to quiet down the exhaust while headers tend to have a mild ringing to them. I would think that your gains should be around 10% (30 horsepower improvement on a 300 hp engine) but I guess that depends on how restrictive the original system really was.


[Modified by vettfixr, 8:57 PM 2/4/2003]

Michael Tucker

ohsixx,
i think your getting that 3% from Jet-Hot coating and what i think they mean is that you get 3% more hp over non coated headers?

Mike

Les

I was thinking of posting this info anyway, so now's a perfect time- I hope it's not a dupe.

In the March 2003 issue of Chevy High Performance they did a section on power bolt ons. On page 38 they discuss headers, and their results should silence those who say headers don't make a performance difference. They compared two 350's- one was fairly mild & the other was fairly stout. They ran both motors w/ stock cast iron manifolds vs. headers.

Mild 350 w/ manifolds- 321 lb/ft torque @ 3800 RPMs, 239 HP @ 4200 RPMs
Mild 350 w/ headers- 349 lb/ft torque @ 3600 RPMs, 255 HP @ 4400 RPMs
Stout 350 w/ manifolds- 340 lb/ft torque @ 5000 RPMs, 382 HP @6200 RPMs
Stout 350 w/ headers- 406 lb/ft torque @ 5000 RPMs, 438 HP @ 6600 RPMs

As you can see, the more fuel & air a motor is capable of using the better the results. This should at least give you an idea of what you stand to gain.

zwede

I dynoed with and without headers (graphs on my website) and gained 60hp and 100 ft-lbs of torque. This was a 454, though.

Headers do make for a tinny sound but I found that headerwrap will get rid of it, making for a more pleasing sound (atleast to me).

desi

Boy am I ever glad to read this post.... :)

I just bought Hooker Comp Headers. I had no idea that the performance would increase by 10%. I really bought them hoping to improve a little on performance and a lot on sound. Can't wait to put them on! :smash:

TedH

The increase will vary. If you have a stock engine and add headers, duals and Turbo mufflers, you may see 25-30 hp. Add those headers to an engine that has also been rebuilt/augmented with performance heads, intake, cam, pistons, carb and ignition and HOLD ON TIGHT!!! You will be amazed!

OHSIXX

Mike: Right! I think it came from the JetHot site. ;)

Mac

In my experience, the change of exhaust tone was only partially due to the less restrictive nature of headers. The other aspect is the material itself which is much thinner than normal cast exhaust manifolds. If the header is made of thicker material, the change of exhaust tone is less drastic, particularly the 'ringing' underhood noise which is charactoristic of headers. The exhaust note (at the tailpipe) still depends on the rest of the exhaust system.

The reason many header companies use thinner materials is because it's cheaper and easier to bend & weld. Quality headers cost more for good reason.

The performance gains are relative as having less restrictive exhaust is only part of the performace equation. If your old exhaust system was restrictive and the rest of the engine is ready to run, headers will make a great difference. If your engine is undercarbed or undercammed, headers won't make much difference at all.

Alwyn678

Bingo.........The headers really add more to a performance engine :yesnod: