Big Block Exhaust 2.5"? - Impala Tech
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post #1 of 6 (permalink) Old 10-09-2009, 09:51 PM Thread Starter
Join Date: Oct 2008
Location: Jacksonville, FL
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Big Block Exhaust 2.5"?

Finally got the car on the street but the 3" bolt on glasspacks are way too loud so I gotta spend a little more to get it ready for my wife and little girls. How large exhaust pipe should I go with? Its a warmed over 396 .30 over with a decent cam, big heads (square port - probably too big), 770 Holley street avenger carb. I really need something thats not going to scare my girls, they are 2.5 and 2 months. I was thinking 2.5" exhaust dumping behind the rear wheels with Magnaflow mufflers. Priced local shop at $450.00. Same system, w/ X pipe for $570.00 and H pipe $$500.00. Any thoughts guys? May swap the cam and heads out later for a lower RPM range in the distant future.
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post #2 of 6 (permalink) Old 10-10-2009, 10:07 AM
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2.5 is about right for a mild 396. I would avoid the exiting behind the rear wheel idea in my opinion. It makes for a smelly ride especially when sitting in traffic idling. My flowmaster system on my 66 396 is perfect. It's loud when I'm on the gas but when cruising it's quieter. My tailpipes run straight out the back under the bumper, so all the "noise" is behind me. Your noise tolerance may be different than mine, but my two boys don't mind it at all! My oldest is 3 1/2 and the youngest is not quite 1 yet. They are used to the sound of a big block!
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post #3 of 6 (permalink) Old 10-10-2009, 10:39 AM
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I favor a 2-1/2" system as well. Mine also exits out the back under the bumper and I have dual stainless steel bow tie exausht tips to give folks something to look at as they wonder why my car sounds different dfrom all of the other Impala's that they have experienced from the mid eighties. I am running a 406 so same number of cubes as far as noise generating capability goes.

Big Dave
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post #4 of 6 (permalink) Old 10-12-2009, 11:18 AM
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I have a .030 over 396 and a mild Summit cam in my sport sedan with 2.5 head pipes through Dynomax super turbo mufflers and full 2.25 tail pipes to the back. System has a little rumble to it but sounds great under accelaration and cruising. When I got the car it had turn downs before the axle and it was really noisy inside the car.

I also have Fatmat under the carpet and on the lower firewall. Really helps isolate road and engine noise and insulates too.

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post #5 of 6 (permalink) Old 10-12-2009, 11:25 AM
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I like 2.5 exhaust too that's what I run out the back though. I think my mufflers are 40 sires flowmaster sounds decent.

Make: Chevrolet
Model: Impala
Year: 1971
Doors: 4
Motor: 400 V8
Tranny: TH350
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post #6 of 6 (permalink) Old 10-12-2009, 05:21 PM
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Thumbs up

if it's a street driven car only, then yes go with the 2 1/2" .. but if your racing it go with the 3"

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