Seeking a quiet muffler
 

Gentlemen: I have a 1967 GTO equipped with a 500 hp stroker motor, TH 400 transmission and turbo mufflers that I can no longer stand because they are much too loud. Any recommendations for a free-flowing, quiet muffler for my car? Thanks for your input!

Dyno max super turbos. Quiet and flow good.

Borla, straight through, but quiet till you get on it. Normal driving is like stock.

Most exhaust shops work on modern vehicles... they wont know what is quiet on a 500hp stroker engine. Guys on a forum that own or build these engines will have more experience than the average shop these days.

Also, "quiet" is very subjective, one persons quiet can be another persons loud. is it drone at a cruise RPM or the sound at idle that you dont like?

If you already have turbo mufflers and dont like them, its doubtful going to another brand of turbo mufflers will be any different. But they do make a longer case turbo muffler thats supposed to be quieter than the short ones.

Most straight through mufflers will be louder than a turbo muffler just by design, if a turbo is too loud a straight through will most likely be louder.

A muffler has a hard time making a 500hp engine with headers and big pipes be truly quiet and free flowing usually is louder than more restrictive quiet mufflers, so its gonna be a trade off for sound vs flow.

If you do have headers, the biggest sound reduction will be using manifolds, even the high flow RPM manifolds are quieter than headers. Also I found that an X pipe in the system will help to quiet the exhaust while providing better performance.

i have 3" walker super turbo with headers its real quiet can have a conversation in the car no problem (and its a convertible)

A friend of mine is running headers to 3" mid pipes with an H pipe, reducing to a pair of 17749 large case dynomax super turbos, then 2 1/2" tailpipes. It's running a healthy 467 with an 041 cam, and has no godly reason to be as quiet as it is now. It runs and sounds great.

The 17749 mufflers are my favorite.

Almost as quiet as a factory muffler and great performance.

I run them with a Flowmaster mandrel bent aluminized 2-1/2” system with H-pipe on both of my 1964 A-body Pontiacs.

Not all turbo mufflers are created equal, the cheaper/generic ones can be too loud and annoying.

Good timing on this thread, I am in the same boat. I am done with a stupid loud obnoxious car. I also came across the Dynomax ST's in my web travels mentioned on other sites. I'm almost ready to get a pair of factory style low-flow mufflers.

I'll be tuned in to this to see how it develops.

Glad to see you posting again!! I missed seeing a lot of your work and ideas.

I am also tracking this, as the glass packs need to go soon. They don't play well with others...

Another vote for dynomax. I'm running them on 2 cars one making almost 800hp and they do an excellent job of taming noise. I'm not a huge fan of obnoxious loud either but I am very performance oriented and dynomax is probably one of the best at both of those categories.

You can do the dynomax turbo and even their ultra flow design is relatively quiet compared to other mufflers if that caliber that I've tried

I've been running a 2.5" exhaust with X pipe with the DynoMax 17749's in my '64 GTO convertible for 10 years. I primarily drive with the top down and the exhaust is far from loud. I put these on after installing my 462 in 2013. This exhaust replaced the 2.25" exhaust system that I had put on in 1994 when I was running the stock 389. Figured bigger motor needed a bigger exhaust. I'm very happy with it.

Get the longest case Dynomax Super Turbos you can fit. They will be the quietest.

BTW, if you have 3" or larger tails, you're simply NOT going to have a quiet system.

https://www.youtube.com/watch?v=PMunVfwROfk -Super Turbos

https://www.youtube.com/watch?v=ly5IlDyXFbo -Goerlich Xlerators

Eh, that's not always the case. We have 2 cars here with complete 3" systems and they are among some of the quietest and comfiest cars to cruise in the whole fleet. No drone, easy conversations, and you can actually listen to the radio on a low volume.

Hands down 17749s are the best quiet choice out there. It's my go-to.

You might be able to squeeze a longer case than 20" under there but you have to check. I don't think you need to, the 20" ones are pretty dang quiet.

I ran the Goerlich for a while, liked them, but went back to STs.

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A buddy had Dynos on his 62. They were loud. Borla, straight through, stainless steel, million mile warranty, packed with stains steel wadding, and quiet. You can’t do better than that. Unless you want it to sound like a mustang lol

Here are some tables from Jim Hands Muffler Test:



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You might look to the OE's. There are numerous vehicles out there today with as much or more horsepower that are able to pass government noise standards. You may have to get creative with mufflers and resonators like they do. I've heard several people recommend late model Cadillac mufflers.

Thanks. I'm done with racing. My co-worker got working on his 66 Barracuda, it it resparked my car interest. I was an inch away from trading for a 77 TA clone with t-tops, but cancelled the deal.

Now I have to detune my 67 FB to make a comfortable cruiser. Gotta start with making it quiet and spider free so my wife will go on a few distance cruises with me. Part of that will also be gearing back from 3.73 to 3.08, maybe lower.

Thank you for the data. I was hoping to find something like that.