I put the Dynomax turbo mufflers (short ones) on the GS400, to replace the max-drone, echo-chamber, flow master copy mufflers that were on it. They helped this issue a ton, but it still drones some from 1500-1900 RPM under load. The exhaust turn-downs sound like an interesting thing to try. Currently they're 90 degrees, pointed at the road. I may try some 45-degree ones and see how that works. Oh... 2.5" Pypes system with X-pipe and TA down tubes on stock manifolds.
I run the Flow -master Delta Flow 50 series on my 69, Part # 942553 , There a little expensive but even buddies of mine who like it loud have used them & been happy......
Well folks, thanks to this post I’ve confirmed that the placement and direction of my tailpipe exits are a big contributor to the unpleasant drone. I drove over a nearby drawbridge and once I hit the steel grate deck, the car went quiet. Once back on pavement the drone resumed. I’m now on a mission to aim my exhaust exits elsewhere. Some baffled tips arrive tomorrow. I’ll need to adjust hangers to get the tails out from under the bumper a bit and probably cut the turndown ends off.
So maybe the exhaust needs to just go straight out from the bumper. Now that makes me wonder if the thru the bumper exhaust has less drone or none. The X pipe did help mine my exhaust goes out the back but does point down after the muffler. Wonder if the outlet was bigger on the end of the tail pipe cut more off the bottom of the pipe make it more egg shaped but keep the end tip pointing down.
The exhaust tips I ordered came this evening. They’re going back. I found a tip that would work if the pipe were the right diameter. It’s a shame coz I think it’d look nice. It’s a simple chrome 45 degree elbow that could be attached to the turn down ends of the pipe and the extension goes straight back. Can’t find a 2.5” version. I think I’m going to try making my own extensions. I’ve got some small pipe segments I may be able to weld together so I can add them to the ends of my tailpipes.
I cut the downturned ends off the tailpipes where the tailpipe is straight, and slipped on a 45 degree elbow so the exit sits at the end corner of the bumper, right under where the quarter meets the side of the bumper. It’s angled a little bit downward but not pointed right at the ground. Actually looks pretty cool there. But I still have about 60% of the drone I had before. It’s gone driving over the drawbridge grate, and standing directly behind the car it’s quieter with the engine sitting in the RPM drone zone. they point away from each other so you hear the note they’re playing when standing at the corner of the car facing the rear marker light. Since I don’t like how low the exhaust is sitting now I’m going to see if I can put the resonators along side the tank before the exhaust tips, so I can tuck everything else up better. I think having the resonators at the end will work better than up front. Quiet the note the system is playing right before the sound exits. Like a trumpet player holding that rubber plunger-looking thing over the horn’s bell. if that doesn’t do it, then I’ll try building a j-pipe resonator to capture and return the sound waves out of phase for noise cancellation. Probably should have done that at the get-go. Live-n-Learn. you may be asking “why don’t you just change the mufflers already?” And the answer is because I’m stubbornly hanging onto the idea that since what I had before (plain old exhaust shop mufflers) also droned, I’ll get another set and find the same issue because it’s the configuration of the pipes, the car body, engine, whatever just making that note amplified. I’m not gonna re-pipe the whole thing. I also have this issue with not letting inanimate objects get the best of me. bear with me. I’m going to reach exhaust utopia
There is another physics approach besides the J pipe. Just a T with a pipe at 90 degrees. Vary the length as you would would the J pipe but easier to install. I plan to try this using a "H" pipe kit like: https://www.walmart.com/ip/Universal-Dual-Exhaust-H-Pipe-Balance-Tube-Kit-2-1-2-Inch/106771867 . I think putting it before and above the rear axle might work.
Add one of these on each pipe somewhere. It will kill the drone. https://www.summitracing.com/parts/...x3UQjtPpQk_k1Cfq4u_h7iRaZGii-AmsaAsRfEALw_wcB
I would have gotten the exhaust situated the way I want it today, but last night my wife’s CR-V - that we just made the final payment on - left her stranded. I was in the garage when she called and brought a battery and some tools. She was a mile from home. This morning I replaced the alternator. Then I resumed working on the Buick. But since I was exhausted I gave up and it’s still not done. However… There are some Dynomax Race Bullets waiting to go in. I tried them by slipping them over the turnout elbows I’d added. They totally eradicated the drone. Yay. I’m trying to put them along side the tank, and they’ll exit out from under the bumper I guess. They’re kinda long. So from the back of the car they’re not going to be hidden, exactly. They might end up being visible from the side of the car as well. I am leaving the vibrant ultra quiets in, near the front. The 17749s before the rear end, then the bullets at the end. Not sure how it’ll work out. Maybe I’ll swap the bullets and ultra quiets, not sure if they’ll be more or less visible. Putting the bullets between the ultra quiets and the 17749s seems like an option but not sure if it’ll stop the drone or not that may be coming in part from the tailpipe shape. When I tested them on the ends of the tailpipes they made the car really quiet but I liked the way it sounded. It’s going to be ugly weather-wise this week so I guess this isn’t getting done just yet. Sigh.
That may be possible. I took a video of on the road drone after I put the ultra quiets on, but not before. The drone was reduced but still there. I’ll see if I can put something together.
Six is better. It’s an even number. Half dozen. At least the Vibrant ultra-quiets and the Dynomax bullets are straight-through. No decrease in diameter inside. They’re really only there for disruption of sound waves. The 17749 super turbos are probably the most restrictive part. If I had to do it all over again from scratch I’d have gone with an OEM-style exhaust. 2.5” was overkill for my needs. With 2.25” and some quality mufflers I’d have been done already for a lot less money. I already put EFI on the thing so what’s a few more bucks I’ll never get back. It’s a car that’ll hopefully remain in the family. Nobody else will want this cobbled-together-from-multiple-Skylarks abomination anyway.
If you go to Holley's website you can see which mufflers are the quiet ones After the Delta flow 50's there is another 50 that is called SUV and is quieter than the Delta 50's There are actually 3 others that are quieter than the Delta 50's I went there to buy the headers that were on sale and I looked at the Flomasters while I was there too since I need a set also.
Non-Flow thru, non performance, stock mufflers are your answer. It will sound quiet & smooth and ride like a Cadillac. If you run headers, you'll have just a bit more hollow tubular sound from the multiple thin tubes that I personally like. Yep, post vid & let us know what you end up with and how much you spent plus time and effort for the result. Maybe buy an electric car? They're quiet with no drone...
