Technical What Mufflers Do You Run On Your Hot Street Car?

And that's the sound I am looking for my build THNX !

 

If you can figure out how to keep these resonators from blowing out your rearend, they really cut the drone with just the right amount of backpressure. $2.99 for a 3-pack at my local ShopRite. 8^) Jack E/NJ

 

https://www.jalopyjournal.com/forum/threads/the-right-sound-choosing-a-muffler.1118367/

 

Jnaki, I really enjoyed your story about the 58! My cousin in the USMC has a 58 Biscance and he will really enjoy reading that. As for the offroad mufflers, that is yet another period muffler that I hadn't came across. Sounds like I'll be looking into them

 

smithy's on the shoebox, superturbos on the '72.

 

Hey S,
Thanks for the nice comment. In order to be somewhat competitive, we even had a set of dual pipe scavengers made to bolt on to the down, exhaust flanges under the stock headers. It was louder than stock, but a different sound. There were others that did the same. Finally, someone complained to the tech committee that those were direct exhaust cut outs that were open, giving an advantage over other "through the muffler" stock cars.

So, those scavenger pipes were outlawed at the drags for the stock class. If left on, we could have gone to the Gas Coupe/Sedan class, but the scavengers did nothing to the speed or times. They were used several more times on the street/cruising, but ended up in the rafters of our backyard garage until 1998.

The direct down pipe, cut outs were loud and did have an effect on the speed and elapsed times. But, in order to stay in the stock class, they had to be capped up. The tube mufflers were also an advantage in times and speeds.

Jnaki
Speaking of 1958 Biscaynes, here is a half-time intermission fun race staged while the elimination races were being charted in the tower at Lions.

A 1958 Biscayne with his open cut outs, racing against one of the newer 335hp , 4 speed 59 Impalas in the famous Le Mans style races.
1959 lions dragstrip

That 58 Biscayne had 315 hp and was one of the top racers in our class. Eventually, he went to the Gas Coupe and Sedan class with more mods.

 

Mild BBC with 2.5" exhaust, an H pipe and Flowmaster Delta 50's

https://www.facebook.com/video.php?v=499675440418896

 

Quiet ones At the age of 17 I came to the conclusion that loud ment look at me I need a ticket.

 

Smithy's

 

Smithy's for me. Ceramic coated but still that great Smithy sound. I think these are 25" long?

Piped out the back, no h pipe -true stereo sound, flathead supplying the input

 

Not big HP but amazingly quiet. 2.5" with custom X-pipe and 15" SS Kook's race mufflers.

 

Running some stainless glass packs on Taboo. Got them on sale through summit. They don't sound too bad, the gear drive makes more noise than the exhaust.





I have Cherry Bomb's on my 68 C10, they were on the truck when I bought it and I want to toss them in the dumpster.

 

Look at Flowmaster "conical" round muffler technology .... you will be glad you did !!! MERRY CHRISTMAS !! best present you got today !!

 

Is that the HP-2 muffler?

 

Smitty's from day one or Porter's.

 

I run flowmaster 40,s on my 54 with headers ,turned down in front of rear end.They have A nice throaty sound.
I run flowmaster super 44,s on my 72 Buick skylark, pretty throaty,even with manifolds.
I have been seeing videos of Black widow mufflers, they got A great sound too me.

 

Since I did a few favors for Borla I got them to do 2 systems for me. One on my 1964 Ranchero with a hot 302 and another on my 1952 Plymouth Suburban with a hot 392 early hemi. The systems are all stainless from the long tube headers back and have Borla mufflers. They both sound great !!!!

Jan in Ojai, Ca.

 

I put these on a flow bench and they were terrible! I was trying to get under 95db with a minimum CFM rating ! they weren't good at all.

I also tried dimpled baffles and they stalled the air as well.

The best type were Vee shaped central baffles with inverted Vee so the sound waves cancelled each other

seen here on a patent application [on the RH side of the pic]
It flowed a lot of air and just creeped under the 95 decibel limit on my Road Race Corvette

 

I assume these are the oval style muffler. Did you test any round, small diameter muffler's? I am building an under chassis exhaust system in a tight space.

 

Having had a fair amount of different car/motor combos. No muffler/exhaust sounds quite the same from car to car or motor to motor. But here are a few I have come up with in the past. Had a 350/370 in a '68 Nova...used 2.5" exhaust and mufflers from a CJ Jeep 304 single exhaust. Sounded really nice and the mufflers are very compact. 440 in a '67 Coronet...3" exhaust and Dynamax turbo type with turn downs at the rear axle. This also sounded very good. My current car has a 426 wedge with fenderwell headers. I capped them off and came out the side of the collector to mufflers out of Vette side pipes. I have them hidden under the running boards. Really does sound like a 427 Vette. Plus I can uncap the headers very easy at the track. Gene.

 

They were in 5" round side pipes on My Corvette. [pictured below]
The car is off topic but this thread is focused on the mufflers, not the car.

I needed to get 1380 CFM per pair [690 each] to not lose any horsepower.

The spirals were expensive to make , and flowed not enough to meet the target [490 cfm if I remember correctly]
The Vee baffles flowed 688 CFM each which was close enough and the car was 95.6 Decibels
I eventually pointed the exhaust tips at the ground and the Decibels dropped to 94.

The Vee baffles were easy to make. We carefully slotted the outer tube and slid them in , spot welded them and trimmed them up. Then we TIG welded the slots and cleaned it up.

The mufflers were made in 1996 and are still going strong now.


You can see on the photo, I used truck Reducers and tips with 5" tubing in between. The went straight onto Hooker side-mount headers

 

On a side note:
Years ago, I was shown the results of some dyno tests where a manufacturers muffler actually picked up horsepower over open headers.
It was used by their spin-doctors for marketing.

What wasn't told, Is they had a special cam ground for the test. The cam had long exhaust timing that required backpressure to help it maintain cylinder pressure. [similar to 2 stroke technology]

So if you're wanting to use a race engine with mufflers, it is best to talk to a cam grinder that knows what he's doing [not a "we recommend what we've got" type salesman]

 

68-70 Camaro had a dual inlet/outlet muffler that flowed okay for the 355 cu in my coupe. Mounted immed. behind the pumpkin, quieter w/8 pulses than 4.

 

Single exhaust is now the standard in Road Racing. 8 pulses are a lot quieter than 2 lots of 4 [it smoothes out the pulses and also the flow]
With a good Big-Bore exhaust system they can make a lot of power.

Another thing we played with was an "Atmosphere Box" which is a box 3-1/2 times the engine capacity with 2 inlets and 1 outlet.
The box had no baffles internally but had external sound insulation wrapped around it.
It wasn't square or rectangular but tapered approx. 70 deg each side of the inlets .

This idea was to fool the engine, by dumping exhaust gases into an artificial atmosphere .
There was minimal loss in flow ,but it barely scraped under our 95db limit on a Smallblock Ford

Remember Gases Flow and Sound-Waves Bounce/Rebound

 

So, just to clarify, the spiral baffles you tested were baffles you made, not the baffles I posted a link to, correct?

 

@Kerrynzl, spin the tips inboard, preferrably pointed directly at one another (ASSuming they hang low enough). The exhaust pulses will be acoustically out of phase with the opposite side and partially cancel one another out. There will be a partial phase cancellation even if they can only be pointed mostly toward one another (ie, turned inboard to 45° angle). The key is to get the sound waves running into one another in some fashion. Also, some of the acoustic energy will dissipate into the bottom structure of the car (which may not be a very enjoyable sound, but... hey, it's a race car).

Obviously, this is just simplified commentary that may not be practically applied to your car, but I have a solid background in acoustical engineering, and specifically with sound damping methods... and the concepts are sound (bad pun).

 

2 1/2" steel packed Porter Shorty mufflers behind the 351C. With no carpet or insulation, they are pretty loud when you get into it.

 

Yes they were made to fit in 5" tubes. We started cutting out spirals to improve flow, eventually we only had 1 x 360deg spiral and it started improving flow.
We also changed the angle/pitch of the spirals .

We couldn't do this with a Corvette frame. The side pipes were raised so the lower edge didn't hang lower than the frame [the car was lowered]

If I could've done what you suggest, I would've done an 8 into 1 system. I didn't like the sound from side pipes .you can only hear one side, making it sound low revving [in the car was different, I shifted at 7200rpm]
Asphalt is a good sound deadener.
In NZ if you got pinged for noise, it was fix it or on the trailer

 

Thanks for the real world info. Cool Vette by the way!

 

BTTT. To summarize so far;

1. "Good sounding" is extremely subjective.
2. Pipe diameter, X- & H-pipes, and exit location all affect sound as much as muffler selection.
3. Chambered mufflers (e.g. Flowmasters) sound "modern".
4. Cherry Bombs are really loud, unless you use their longest version (~30"?) and run full tailpipes to the rear bumper.
5. Walker/Dynomax turbos & bullets seem to be a popular compromise between sound (loud) & performance.

Anyone else?