aquanuke

JPI, would headers for left hand drive also fit on a right hand drive car?

Hermosa

I find this hard to believe. Fluid dynamics would show a lot of turbulence in those pits and edges which equal friction/resistance which is less flow.

Who else has these and are all of them that rough on the inside? I would probably get someone to fill in the inside with more weld and then polish them down.

I am trying to contact the manufacturer. I wonder if they can make compact equal length headers.

aquanuke

Sorry about the large images, I thought I would keep them original size to make it easier to see the welds.

Hermosa

Are the stock headers the same for the SC400, GS430, and the SC430?

Also, can you resize those pics? It is really easy to in even MSPaint.

aquanuke

Ive resized them

D-MAN63

I want to do these bad.. but afraid of cracking and its a pain to install.. but the sound is sickening .

JBrady

The quote of mine you used above refers SPECIFICALLY to the FINAL welds where the 3 bolt flange welds to the collector. The welds on the inside of the tube probably HELP flow since the inlet to the catalyst at that point is smaller than the collect inside diameter on the S&S. I had actually wanted a 2.25" collector but that made manufacture difficult so 2.5" was selected. So, the weld on the inside actually reduces the sharp edge transition from the collector to the catalyst inlet.

Make sense?

Not only unlikely but unnecessary. Very short pipe tune at very high RPMs. You would never reach the tune RPM for equal length shorties. That said the space limitations in the car as such that not much else will fit. All street parts are compromise. The S&S compromise is not perfect but much better performance than stock.

Hermosa

I doubt those welds would help flow in any manner. Changing diameters does alter flow as well especially if it is abrupt but obstructions hurt alot too.

You are right that these will still be better than stock though. I guess I just look at it from an optimized point of view. I admit I am a bit frustrated when it comes to exhaust fabricators because the potentially good ones probably all work in labs and not in automotive shops.

JBrady

I refer back to this thread from time to time and send others here to help them understand the answers to their questions.

I know Lee intended to update the server links to many of the non-working pictures in this thread and if he gets time that would be great.

Regarding the specific question above I have meant to make a response but always seem to be distracted. Here goes:

Often a welding bead (especially MIG) is raised and rounded. This is the case with the internal weld in question. This weld is on the inside of the collector and joins the 2.5" collector pipe to the 3 bolt cat flange.

Since the weld bead is raised and rounded it slightly reduces the inside diameter. This actually HELPs because the cat INLET diameter is less than the 2.5" collector pipe inside diameter of apx 2.37".

This means that instead of the high speed exhaust gases colliding with a sharp step leading into the cat they instead get a slight "help" in this transition from the raised and rounded MIG welding bead. This is kind of like the aero dams atop 18 wheeler cabs to help transition the air from the cab to the otherwise 90 degree trailer.

Now, this was not the engineered intended reason for the placement or design of the weld but it does in fact end up helping. To what measureable extent that has not and probably will never be measured but every bit helps.

It would be nice to do some engineering trials with optimized exhaust manifolds and systems for these engines but the end result probably would not be practically packageable in the car. From a compromise standpoint (everyting is) these headers work pretty well.