My ‘72 Skylark ragtop with a 350 and stock manifolds had an exhaust system on it that seemed to be cobbled together over the years by muffler shops in Brooklyn (where the car lived til I got it). Two different mufflers, two different outlet configurations, pipes that varied in diameter depending on the patched section being measured. It had one muffler that ballooned in a backfire incident. Needless to say it was time. And it droned. I wanted the right pipes so I ordered a 2.5” kit with downpipes from TA. They told me to buy offset inlet/center outlet. Nope. That was not gonna work. Those mufflers went back and I got the Dynomax Super Turbos 17749. I wanted quiet but muscular tone. I got that. Along with drone at anywhere from 1790 to 2000 rpm. That’s where I’m at while going down the road, so the drone wasn’t gonna do. I weighed my options and skipped the sound deadening material and skipped fabrication of some j-pipe 1/4 wave resonators. Instead I bought a pair of Vibrant Performance Ultra Quiet resonators. They ain’t cheap but the reviews are good. Amazon has them for $102 each. One arrived Saturday, the other on Sunday. I wasn’t sure I wanted to be cutting sections out of my new pipes to put these in so on Saturday I tried slipping the one of them I had over the ends of the slash cut turned down tailpipe from TA. It quieted things down at 1800 rpm. Then I disassembled one side of the exhaust, put it where the downpipe meets the mid pipe, basically in the notch of the crossmember, and propped up that assembled side on jackstands and it sounded pretty good at 1800. So I went for it. I’d contemplated trying to put the resonators at the tailpipe end but read that it’d be better to do some sound control up front before the mufflers so I cut and assembled. And today I finished the other side. When I started the car it sounded pretty good. Quieter. More reserved. It took away that wawawawawawa undertone it used to have at idle. Smoothed the sound out. Blipping the throttle sounded like understated muscle as well. I like it. Took it around the block and wouldn’t you know it… it still drones. Not nearly as loudly as before, and it was a short drive, but I think the range in which it drones is smaller. Those TA pipes are resonant. Musical when tapped on something. When I was at my bench grinder using the wire wheel to clean up my cuts the breeze caused by the spinning wire wheel blew across the open end of the pipe like you do over a bottle and the pipe started playing a low note. I am thinking I should have put the resonators at the tailpipe exits to squelch the harmonics. I really don’t want to take the whole thing apart and patch the sections I cut out for the resonators. I keep throwing money at this problem so I’m thinking I’d put some small resonators in the tailpipes too. Also, the rubber hangers that come with the kit aren’t very good. They’re kinda stiff. Probably doesn’t help that the way they’re situated the rubber is bolted to the bracket in a way that the “free” end is up against the trunk pan. Maybe there’s some sound transmission there. Also read that turned down exits that are just under the lower edge of the bumper may be an issue. Sorry for the novel… I’m really tired from three days on my (already bad) back in a cold garage and getting on and off the creeper. I’ll be back under there next weekend I’m sure. I think when I went around a corner something touched something else.
i said it time and time again on these forums that those mufflers drone. before you did all that stuff i would have changed them out to walker ss quiet flows. there quiet but have decent flow. an x-pipe might help but h-pipes will not.
In 1969, I had a 396 Camaro that had the chambered exhaust option. It consisted of no traditional mufflers but chambered pipe abt 4' long, like Vettes used on their side pipe exh option. It sounded very cool. I don't know if that chambered pipe is available but it was way different than traditional mufflers. Our cars are nothing compared to the Mustang and Mopar kids breaking the sound barrier everywhere they drive...
The Dynomax 17749s seemed to be the go-to for lots of people based on reading posts from owners of other V8 powered vehicles. Not many mentions of drone. Maybe I should have gotten the Walker SoundFx mufflers, they’re supposed to sound like stock. It would have been cheaper to try those than add $200 bucks worth of resonators. I’m not making the best decisions lately. There are a lot of things that come into play for unwanted harmonics. I guess I’ve got them. I need to replace the convertible top pump. Maybe when I do that I’ll add some sound deadening material too.
First, crank timing up. 12-14 initial. , then mill heads 30 -40 thousand. Crank compression up . Get a 2200 -2400 torque converter for small block. . A 3.08 rear gear. Totally change the setup
They do have rubber but straps but they’re really stiff. They’re thick multi-ply rubber with holes. At one end is a metal bracket riveted to the rubber, and that bracket goes under the exhaust clamp. The strap is bolted to the bracket attached to the frame, using a hole in the middle. There is part of the rubber that is sitting up against the body of the car. It probably could transmit noise. I think it’s a harmonic frequency, where at certain rpm the pipes play a note. I think a resonator at the tailpipe end might break up that note.
ask the tech people at walker they will tell you the dynomax will tend to drone and sound like there is a hole in the muffler under mild acceleration. walker sound FX mufflers are louder and flow less and will not last as long as the quiet flow ss walkers.
Do you have an H or X pipe crossover? DynoMax 17749 with resonator tail pipe tips. No Drone. Resonator tips: UNIVERSAL FIT ROUND 3-1/2"STAINLESS EXHAUST MUFFLER TIP PIPE RESONATED MT-2403 | eBay
Following. After my switch to duals, with a crossover pipe, I get a drone at 35 MPH. Seems to be a period vibration, as I can feel it, and see the mirror vibrate. The factory panel between the trunk and rear seat didn't help, but the summer project of new sound deadener made a difference.
I have Dynomax 17749's on both my '64 (nailhead) and '68 (BBB), the nailhead does have some drone about 1600-17000 RPM, but it is not a "place" I spend any time driving, so it really is not a problem for me. The '68 does not have any drone at all at any RPM. The '64 is manual, the '68 is auto, Not sure if that makes any difference of how the engine is making power to "hold" RPM on the '64 vs. any "slip" on the '68. The only other difference is the '64 pipes run all the way out to the bumper, and the '68 dumps right in front of the axle. (about 1 foot of pipe extending from the rear of the mufflers) The '64 is a convertible and I have Dynamat under the carpet. The '68 is a "coo-pay" and nothing under the carpet. (not even the old dead horse...) Both cars have H pipe. (if any of this helps)
