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Backpressure??

781 views 1 reply 2 participants last post by  4 Jaw Chuck 
#1 ·
I was reading all about the exaust sound questions, and I was goint to post this question under it... but I want this to be seen.. so I started a new topic.

OK, I understand that on a race car when noise is not a issue they run (many do) open headers.

But in the thread about getting THAT sound, a few mention back pressure for a street rod. WHY??
Is this just to control the sound levels?

I am finishing up my build. A `63 Noavss 400 SB with a few go fast godies. A pair of hooker super comp headers and I am looking to get a mandrel bent exhaust with either a X of H pipe dumping under the car just before the rear axel or turn outs just before the rear tire.
I was looking at Borla mufflers as no one around me has em.
Everyone runs FLOWMASTER or DYNOMAX sysytems.
Now as far as I know the BORLAS are a single straight threw free flow designe.. so what of BACK PRESSURE??
Do I really need to wory about this on a 11:1 compression car?
(no cats are needed,, and I am not looking to add em.)

Any help with this would be great.. cause I am right now in the mind set to run free flows. Boys in blue are pretty slack around my parts unless you start running hard on the street.
 
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#2 ·
Backpressure improves torque production below the peak torque curve and assists in smoothing torque impulses which reduces vibration and combustion pressure spikes in the combustion chamber by the action of exhaust dilution...up to a point.
 
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