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Are the inlet/outlet pipes of the stock cats 2 1/2 " ?

I'm debating stainless works 304 SS long tubes w/a 3" collector which would kinda force me to go w/their 3" high flow cat X pipe but on the other had if I go w/JBA Nickle chrome plated 409 stainless headers , their collector is reduced to 2 1/2 which I am assuming is the inlet / outlet of the stock set up.

Even with the supercharger I figure 5" of flow is adequate. If the Stock set up is in fact 2 1/2 cats & I up the boost to say 10lbs You techs think the stock Cat set up is OK ?
 

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I may be wrong here, but I thought the Cats were welded into our exhaust systems right below the manifolds?


'I havent really taken a good look under there in a while.
 

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roboz said:
Are the inlet/outlet pipes of the stock cats 2 1/2 " ?

I'm debating stainless works 304 SS long tubes w/a 3" collector which would kinda force me to go w/their 3" high flow cat X pipe but on the other had if I go w/JBA Nickle chrome plated 409 stainless headers , their collector is reduced to 2 1/2 which I am assuming is the inlet / outlet of the stock set up.

Even with the supercharger I figure 5" of flow is adequate. If the Stock set up is in fact 2 1/2 cats & I up the boost to say 10lbs You techs think the stock Cat set up is OK ?
1) The stock system is all 2.5" but as Kyle F said the stock cats are welded to the H-Pipe and cannot be used with either longtube setup unless you want to do a lot of cutting and welding. In general the H or X pipe sold by the header manufacturer are the only ones that will fit. for example the JBA H-Pipe has a much wider spread between the 2 pipes over the stock setup.

2) In Geometry you cannot say 2 X 2.5"=5" when circles are involved

The formula for the area of a circle is as follows
Pi x (RxR) or 3.14 x (1.25x1.25)= 4.91 Square Inches per side x 2 sides = 9.82 Square Inches.

R=Radius or 1/2 Diameter

The same formula would yield an area of 3.14 x (2.5x2.5)=19.63 Square inches for a single 5" diameter pipe.

Quite a difference between 9.82 Square inches and 19.63 Square Inches

3" duals would yield 2.14 x (1.5x1.5)=7.07 Square Inches per side x 2 sides = 14.14 square inches or an increase of around 44%
 
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