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Discussion Starter · #1 ·
I am building a 67 camaro right now And just wondering if i'm over killing it with a 3.5 in exhaust.

its a built sbc with a big roots blower tuned on e85 with upwards of 20-25lbs of boost. I got 1 7/8" headers with 3.5" collectors and i was going to run collector extensions to an xpipe to dual borla xr1's then 3" tailpipes out of the mufflers to the rear of the car. Its a street car.

thoughts?
 

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Discussion Starter · #4 ·
It's not about "need". It's about "want".
i dont really care about what it ends up with, just want to make sure i'm not doing pointless things. If a 3" is fine that may be the best way to go. Now if a 3.5" will gain me additional power then it would be worth it.
 

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With forced induction, there's no such thing as too big, only too small.

The overlap in the cam purges the cylinders with boost pressure. Exhaust does very little, if any, scavenging.

Try it with the exhaust, then try it open headered. Make sure you adjust jetting for the exhaust change. If it picks up, the exhaust is too small.

Personally, even with a SBC, with it having that much boost, I think the 1-7/8 primary pipe is too small. 2" would be better for sure.
 

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With forced induction, there's no such thing as too big, only too small.

Personally, even with a SBC, with it having that much boost, I think the 1-7/8 primary pipe is too small. 2" would be better for sure.
agreed. i would go with 2" or even 2 1/8" primaries along with the 3 1/2".

also, what do you mean by a "big roots blower?" do you mean 10-71, 14-71...
 

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WJ is right. Once you boost something, its pretty much a non critical issue. It will be louder though through larger tubing, so if its something you'll drive on the street, I would stay with the set-up you described and no bigger.
 

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I'm with .gearhead, its a want. The bigger the pipe, the better it looks!
I just built a 3 1/2 system for a 67 BB Camaro with the same mufflers. This car is prostreeted and I was able to run the exhaust over the axle and out the rear sheetmetal under the bumper. Made stainless steel trim rings where the pipes come out.
 
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