View Full Version : Headers

08-03-2010, 04:59 AM
Car ST185
Part Headers

Bought some headers off ebay
The internals don't look smooth.
Should they be?
Will this affect performance

08-03-2010, 05:08 AM
If you drive a 185 you shouldn't have a header. You should have a turbo manifold. He inside being rough isn't gonna affect the 2 or 3 hp you may get.

Be careful though. Assuming you drive an N/A car your primary cat is located inside the stock manifold downpipe. So you will have to get an inline cat if where you live have emmissions testing.

08-06-2010, 05:59 AM
I have st1844 all track
Ok manifiold/headers from the exhaust to the turbo.
i have a 3" downpipe with no cat as well.

08-06-2010, 06:05 AM
you have header(s)??????

08-07-2010, 11:24 PM
How do you have headers with a turbo??

ST185 is Alltrac - ST184 is not (I thought??).

anyway - if you don't have a turbo then headetrs are good (better) in most cases - you get more flow and you can maybe get more power by advancing the ignition timing a bit more.

Yet - as mentioned by Grot - if you have emissions testing - you will need to get a aftermarket CAT before your next test.

Hipster Lawrence
08-08-2010, 06:20 PM
How do you have headers with a turbo??

Like this.

08-11-2010, 05:24 AM
is that the manifold...maybe I see why the runners are not smooth on the inside

08-12-2010, 03:11 PM
no it looks a little different to this
But I have seen that design also
mine has shorter lengths

08-12-2010, 03:26 PM
moving to turbo section

08-13-2010, 06:38 PM
there is not aftermarket MANIFOLD better than stock for the ST185. custome will have to be it.

08-18-2010, 04:07 PM
The ebay / SS Autochrome exhaust manifolds have a reputation for not being well assembled. Most that have installed these have not noticed any improvement in performance, however I can't say that they are losing power either.

I wouldn't say the stock EM is the best you can get, however the only people to really demonstrate gains have had their manifolds custom built to match their engines.

Anyway, if you could provide some pics we'd be able to help see if it would be an issue or not.

banshee 101
08-31-2010, 06:32 PM
also if your running the stock top mount intercooler the ss autochrome one will not clear the intercooler

08-31-2010, 07:13 PM
To address your first question about the slag inside the manifold. It wont greatly affect your performace BUT...if a little peice of slag breaks off and enters your turbine? bad news!

I recently had one of those manifolds in my hands (shipped to me by accident) and all the welds inside had been cleaned up quite nicely. Its my guess there are a couple companies selling that design and some are putting more time into them after the welding and polishing. Sounds like you got a bad one.

I would make an effort to clean up as much as you can before taking a chance on something hitting your turbine wheel at full boost.

08-31-2010, 08:10 PM
Car ST185
Part Headers

Bought some headers off ebay
The internals don't look smooth.
Should they be?
Will this affect performance

Yes, they should be smooth...

smooth intake ports and manifold= bad
smooth exhaust ports and manifold= good

please see below;
"A mirror finish of the port does not provide the increase that intuition suggests. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow and in the interest of minimizing exhaust by-product build-up. A 300 - 400 Grit finish followed by a light buff is generally accepted to be representative of a near optimal finish for exhaust gas ports.

The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO (see boundary layer and laminar flow). This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past, which develops a velocity profile (or gradient) across the duct. For surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this."
quoted from wikipedia.org

08-31-2010, 08:20 PM
The section you just quoted has more to do with fuel atomization, surface tension and airflow within the head itself and is being extremely nitpicky (+/- 1%).

Welding slag on the inside of a tubular turbo manifold might create a little chaotic air flow but I doubt it would be noticable on a dyno. Again, the main concern is the likelyhood of some of that slag breaking free. Flow might still be a valid reason to remove it, but polishing it out would be overkill imho.