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.

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.

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.

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.

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.

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.

quiet walker super turbos 3" mandrel system on a 455

https://youtu.be/qHEQ2nuhYyQ

Thanks for the help guys. I greatly appreciate all the input every time I ask questions.

The Dynomax Super Turbo #17749 is one the best mufflers I ever used. At first, they sound too quiet but after they wear in the sound starts to come out of them.. After a few years and 10,000 miles or so of use, they really sound great..

Three years ago I bought a 69 el Camino with a stock 1978 truck 454. Turbo 400, 2:87 rear end.. It had a 2-1/2" Pypes system with Pypes mufflers and X pipe.. While driving home I couldn't get that X pipe off fast enough! lol.. After removing the X I found out the issue was also in the mufflers too. I had two 17749 mufflers in the shed. I went to the local Meineke muffler shop and had the tech make me up two down pipes. I buttoned everything up. Put a zip screw at each connection along with Walker exhaust pipe sealer and Walker stainless clamps for lap joints.. Tightened everything up and let everything dry for 24 hours.. By the way I also squirt a qt of cheap transmission fluid into each muffler. I make sure it gets into every corner with the sound deadener getting thoroughly soaked.. Once this burns out and stops smoking the car will sound fantastic and it will keep getting better and better sounding..
This old Hot Rodder showed me this when I was a kid helping him change the exhaust system on his 49 Merc.. He showed me this oil trick on the Smithy glass packs he was installing on his Merc... I remember him a couple years later saying' look at those mufflers, they still look like new. Its from the oil I soaked them in"... That Merc had a big 1958 MEL 430 motor.. Wow did it sound nice!! It also sounds great on my 454...