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Old 12-27-2020, 08:31 PM
brodad brodad is offline
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Default Cadillac quiet performance exhaust?

Is there such a thing? I have a 64 LeMans that I'm putting a mild 400 in. I am using 2.25'' Ram Air Restoration manifolds and plan on using 2.5'' mandrel bent tubing for exhaust any thoughts on mufflers? I installed a layer of Dynamat style sound deadener and a layer of thermal barrier over the interior also new carpet. H pipe X pipe no crossover any info is greatly appreciated.

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Old 12-27-2020, 10:31 PM
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2-1/4" is a LOT quieter than 2-1/2". Run largest Dynomax mufflers and resonators.

Also, 2-1/2" pipes on 2-1/4" manifold are a royal pain in the ass to do the nuts.

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Old 12-28-2020, 12:45 AM
brodad brodad is offline
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Thanks for the reply. I hadn't considered the larger pipe diameter being an issue . For my power level 400hp tops I'm sure 2.25'' will be enough.

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Old 12-28-2020, 01:09 AM
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My 71 Lemans had a shop bent setup with large mufflers and cross pipe; quiet and good flowing.

Then I got a bug to refit with mandrel bent 2-1/2" and X-pipe - much louder. I may mod it to take resonators in the 1968 position after I finish with the refit.

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Old 12-28-2020, 11:57 AM
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Cadillac quiet and performance is a tall order.

I agree with Scarebird though, you'll want the largest set of Dynomax mufflers you can fit. The 20" case Dynomax turbo mufflers are probably your best bet. The Ultraflows are a little louder but still very pleasing by my ears.

They are probably the best flowing mufflers out there while creating the least amount of noise.

I prefer to run X's on all my stuff and don't notice any significant sound differences as long as I'm running the Dynomax mufflers.

What I have noticed though, switching 2 of the cars here back and forth between ram air manifolds and full length long tube headers, is that the manifolds actually produce a noticeable increase in the noise level out of the tail pipes, especially through the mid range. When long tube headers are installed it quiets things down quite a bit from 2000 to 3500 rpms, especially noticed during cruise and light throttle. I actually thought it would be the other way around but apparently the scavenging affect of the headers helps. The manifolds package a lot nicer though.

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Old 12-31-2020, 01:14 PM
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My GTO has headers, 2 1/2" head pipes, 2 1/4" tailpipes and Waldron resonators. The mufflers are the long Dynomaxs. It also has an H pipe. Its really quiet. At WOT the air intake is still louder. Use Remflex header gaskets; they really seal well. If you want a little GTO style throb to the exhaust don't use an H pipe or an X pipe. The X pipe makes the exhaust note a little higher tone. I have one on a different car. They also reduce noise.

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Old 01-01-2021, 05:58 PM
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I used to use Cadillac 1977 mufflers on my 340 barracuda. They were 2.5" in and out, very fat, and were used with out Cat converters (I think) so they really toned it down. I'll see if i can find the Cad they were used on.

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Old 01-04-2021, 08:23 PM
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Walker 21856 is very close to what we used to use. I suspect it sounds good and works pretty well since it was used as a single muffler n the 1977 425 cu in Cadillac.

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Old 01-04-2021, 09:48 PM
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quiet walker super turbos 3" mandrel system on a 455

https://youtu.be/qHEQ2nuhYyQ

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Old 01-05-2021, 07:26 PM
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Thanks for the help guys. I greatly appreciate all the input every time I ask questions.

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