Muffler recommendations
 

Just had a new exhaust installed on the firebird and don't like the sound, too loud and it just drones. I wanted something a little louder than stock but now I want something quiet. Any recommendations? Its a 69 firebird with a 350 manual trans and stock exhaust manifolds.

Dynomax Super Turbos - No drone, very efficient and would fit your desire for a "little louder than stock".

I agree with above answer. Just wondered what’s on it now?

I have Dynomax Super Turbos that I am planning to put on my car because I want it to not be loud, but I'm surprised to hear folks saying they are efficient and don't hurt power too much. There have been episodes of Engine Masters which show the turbo style mufflers were significantly restrictive and down on power compared to chambered style mufflers. Agree that if you just want something for a cruiser that is a little louder than stock, turbo style mufflers are a great option. But I'd stop short of calling them efficient.

Also FWIW, the 2.5" Dynomax Super Turbo mufflers actually neck down to 2.25" inside, but the Summit brand turbo mufflers are a true 2.5" all the way through.

-The straight-through mufflers with packing (flow piping doesn't do 180* turn) flow the best.
-Turbo mufflers where the exhaust has to 180* and back again, are less efficient.
-Chambered mufflers vary a lot by manufacturer design. They rarely, if ever work as well as straight through. But comparing to turbo-style some are occasionally marginally better, many often worse.

Turbo mufflers were installed, not sure of the make.

As far as the Dynomax recommendation, what you want for quiet is the 17749 long case super turbos. I have regular 14" ones on my Catalina now and will be switching up soon after riding in a friend's 64 Catalina with the long case ones. He has a Len Williams 455, 041 cam, Rhoads lifters and long tubes. Exhaust is 3" with H pipe to the mufflers and 2.5" tailpipes out the back. The car is damn near silent inside even cruising at 3k rpm.

I have a 78 T/A with a complete RAIII and RAIII manifolds. In the 80's my car would blow exhaust manifold gaskets constantly. I tried every kind of gasket to no avail. I always thought I needed to bring the manifolds to a machine shop to have them cut. I came across a set of Flow Master two chamber mufflers and put them on. I never blew another manifold gasket again, its been 40 years. Point is, Turbo mufflers not as free flowing as one would think.

Jim and Tom Hand would dispute your claims. Per their extensive testing on Jim's '71 Le Mans 455 powered wagon, the Dynomax 17749 had one of the lowest backpressure ratings, the lowest sound level, the fastest speed in the 1/4 mile, and the 2nd quickest time of all the tested mufflers.

https://www.pontiacstreetperformance...p/exhaust.html

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Love my Borlas, straight through, but not loud. Million mile warranty too.

It also had the largest body, which is also a factor. But if you compare similar sizes like the 17734 and Cyclone Turbo, the straight-through Borla did better in backpressure and 1/4 mile ET.

The chambered flowmasters were all on the low end of performance. Supertrapps are kind of their own animal since they're essentially a tunable tailpipe. Not sure what the AP Xlerator or discontined CVX muffler designs were like inside.

I put 17749s on my brother's 1970 LeMans vert with a 530 Hp motor and 4 speed. Was going to go with the Dynomax Ultraflows, but it would have been too loud with the top down. The 17749s are perfect sound wise and no drone. I used a Pypes 2.5" mandrel bent system and 2" headers.

With a Torque Tech mandrel bent, with band clamps that didn’t bent the pipes, I didn’t like how Pipes puts their Logo on stuff, you can’t remove it easily, and they were very thin tips at that.
The ones I saw at a show were out of round they were so thin. I had a custom 2.5” set made.

amcmike

I run the 17749's on the GTO. Why look at anything less efficient and/or more expensive - regardless of brand name?

Besides, it's what the OP poster is looking for.

The 20” case 17749 is my go to for both of my ‘64 A-body Pontiacs, however they’re simply too long to fit in the recess under the back seat floor pan of an F-body.

I used a pair of the 14” case 17734 mufflers on my ‘76 T/A and they were a good fit, I suspect your ‘69 has similar space constraints. They were a little more aggressive sounding than the larger 17749 mufflers but still good for something you’re driving a lot. Smaller 2-1/4” tail pipes would tone them down a bit without sacrificing performance.

Ground clearance with dual exhaust and these fairly large mufflers isn’t that great. If a low profile muffler with good sound quality is available I’d be looking into those. There just isn’t much room under the floors of an F-body.

I think one of the tests I saw the TV guys do they were stunned at how well the Super Turbos actually flowed. Not sure they had done lot of studying to see how the flow directors work but likely as not, they did not have time nor desire to advertise one brand over another. They were learning that the front pipe diameter is more important than muffler style, assuming the mufflers are close in flow capability.

On an early Bird, I'd go with a free er flowing crossflow muffler due to ground clearance. Today, I would check with Waldrons for just such a mellow soundling free flowing crossflow mufler. Years ago under my '68 400 Bird convert, I sourced a walker dynomax crossflow w 2 1/4" inlet/outlets (was originally spec'ed for a Buick GN). Worked well but engine was not a max effort 400 build.

Have used numerous pairs of DynoMax 17747's & 17749's under A-body's, & have more 17749's to install on own A-bodys. Both of those part numbers are the longer 20" case, but are fairly thick & under an F-body, unless ones into the Bootlegger look, or the cheap springs/ 4WD look, ground clearance is limited.

As far as Jim & Tom Hand's EXCELLENT exhaust comparison articles, one also has to understand that research is near 25 years old, there are several comparable 2.5" inlet/outlet high flow mufflers avail today which provide excellent flow & sound quality & are of slightly smaller case design & of lighter weight.

One not mentioned is spin tech. Can’t speak to back pressure but they sound pretty good and don’t have any drone. That’s what RARE suggested for my system.

There was a statement about efficiency of turbo style being less than chambered (which I believe the opposite to be true most of the time). I simply categorized the 3 main types so there was no confusion, and then how they typically perform relative to each other.

Then you said the Hands data contradicted my general statements, and I pointed out how they actually supported my statements. The brand names I used in my follow up post was simply to identify and relate back to the performance of the test, to show my original statement was valid. I never implied one brand was better than another. Nor did I say there's anything wrong with Dynomax or that turbos don't flow well.

I didn't realize we weren't allowed to correct information, support our statements, nor add technical content beyond an OP's original question.

The most interesting thing about Jim & Tom’s testing was that they used a single exhaust setup to get that much performance difference out of them.

Oh, I might add that their CD is still more all time favorite music c! ��