430 Had to cut new fabspeed headers

I don't know how comfortable I would be having one pipe a different diameter

 

I would have just gone with challenge headers since the OEM headers fit your modified 430 with the supercharger.

 

It's likely very negligible impact. People have done tests denting the crap out of them with no real impact. It's not ideal but I'm sure it's just fine.

 

Wish we lived closer together - I’m a moderately skilled welder and have made many sets of motorcycle/chopper pipes - coulda hooked you up for a beer!

Kevin

 

It is not a critic, just to be clear: as for me it is a job wonderfully done buy I can not stop to look at it like a malformed limb in a wonderful creature.

 

Thread title reads like a knock against fabspeed.

 

The headers should still have the same flow rate with the constriction. As long as the internal area is the same, you should see no difference at all. Many cars have this (see the Maserati GT/Cambio - the stock exhaust does the same thing in order to clear the steering rack).

The main thing is the length. That will affect the sound as the detonation order at the tip depends on the speed of sound and will vary slightly depending on the length of the tubes. You can take a cross-plane engine and make it sound like a flat plane just by modifying the headers. Velocity AP mastered this with the Aston Martin DB cars.

 

Certainly not the same internal area once the tubing is squished. Not likely a huge problem but I think cutting it out and rebuilding as the op is doing is the right way to go. It will barely change the length.

 

Deleted

 

There are plenty of knocks against Fabspeed on this forum. Some well deserved, some not.

 

I used to think dents in the headers would hurt power and be really bad.

But this makes me think otherwise

 

was about to post this. Yes, it's basically a non-problem

 

Correct - the speed of sound doesn't change, it's the arrival time at the tip. "Equal length" isn't always appropriate depending on the application and sound you want. That's why you can have two sets of SS headers on the same motor that sound completely different. I love to use the Aston Martin example with Velocity AP. I had full custom exhaust on my V12 and nothing, and I mean NOTHING, compares to their headers. The length of the tubes was just right.

 

This is true because if you dent or squash the metal, it keeps the internal area the same as the same amount of material exists. If you were to restrict it in a venturi design (bottle neck) using less material, then you'll have issues.

 

Shape influences area. Take a 2" diameter circle for example. The perimeter = 2*pi and area = pi. If the same perimeter was applied to a square shape, each side = pi/2 and area = pi^2/4 which is less than pi. Same material per unit length in each since the perimeter is the same, but different areas result.

My guess for why the dented tube doesn't impact power that much is that the exhaust gas is a pulse flow, so as it travels through the dented tube it has space in front and behind the pulse it can expand into. If it was continuous flow like water coming out of a garden hose, the result would probably be different.

 

Incorrect, you reduce the internal area. If you flatten it completely it's the same amount of material and well, doesn't flow great.

 

Ok good call lol. I could have made a more valid point by saying as long as the internal area remains the same to some degree, there should be no change. But yes, there will be a tipping point where flow would be impeded but I'm not sure where in the process of changing the shape that would be.

One concern I'd have is the temperature increase at the corrected area, being that the this would be so close to the block. The Maserati squished the pipes downstream, but this one is right where the heat is at its highest. I'd suspect that the change in flow direction internally would build excess heat in and around that area.

 

^Yes. What to consider is, on a mandrel bend the idea is to maintain a consistent inner diameter but still, it is smaller ID in a bend and also, a bend.

By that I mean directional change is a flow restriction, much less so on larger bend radius.

So going back to denting a straight section, it inherently flows better because it’s straight and you can compress it to some degree before that section inner diameter is as small as the ID within a bend.

Agreed not likely to make a big difference but I think best to avoid if you can