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Username Post: Exhaust Drone        (Topic#332624)
Hugh in NC 
Contributor
Posts: 152
Hugh in NC
Loc: In my Recliner Rockingham...
Reg: 08-01-12
01-30-16 05:51 PM - Post#2605525    

I have a stock 1951 235 with powerglide. Single exhaust that looks stock, no special looking muffler or pipes. It has a pronounced drone around 50 mph. Is this a common problem with these cars? Or, is it just mine?

Has anyone had this problem before and what is the suggested solution?

Thanks in advance for your help.

Hugh

Miss Daisy - 1951 Styleline Deluxe 2 Door Sedan



 

56sedandelivery 
Dedicated Member
Posts: 5393
56sedandelivery
Age: 66
Loc: Everett, Wa.
Reg: 02-26-08
01-30-16 05:59 PM - Post#2605527    
    In response to Hugh in NC

Somethings making contact with something somewhere. How's that for not being specific enough. Get it up on a lift, and check it out. Wife got in a rear-ended car accident a few weeks back (he was uninsured!), and it bent the exhaust resonator pipe over the axle. Drove her and I nuts with the vibration against the under-body. I forced a folded up rag under where it looked the most obvious, and it settled it down a bunch. It's finally been repaired; she'd get home after driving on the freeway to come home from work, and she'd be all worked up because of that vibration. Happy wife, happy life!
I am Butch/56sedandelivery.





 
Bel Air kiwi 
"3rd Year" Silver Supporting Member
Posts: 4256
Bel Air kiwi
Loc: New Zealand
Reg: 04-24-14
01-30-16 07:01 PM - Post#2605548    
    In response to Hugh in NC

Hi Hugh, By your use of the word drone I presume you are not referring to a rattle or bang from loose or hitting pipes. So it is more likely harmonic rather than mechanical.
If it has come on slowly then on some occasions the change can be down to the internals of the muffler slowly failing. Alternately the system could have been installed with undue tension due to how its mounted.
When its cold have a look underneath and see if you shake it a little and if you can hear anything inside the muffler moving.
See also if its easy to move or really rigid as that will change harmonics.
If it all looks pretty new and sound and not tensioned up then you could try a tailpipe extension that steps up in size or has a bell flare and if that changes it you know its harmonic.
Have a look also and see how good the hanging mounts are as well.
Cheers Kiwi

PS Butch don't tie rags around the exhaust you are lucky it didn't fireball!

48 3100 RHD, 51 Deluxe 4DR RHD, 51 Bel Air parts car, 52 Bel Air P-Glide LHD. Others 23T, 32 Tudor, 58 Edsel pacer 4DR HDT, 79 F250 351C RHD. 69,70,82 Capri. No mobile, no TV, and no Jap cars.

And when it was laid to waste, they called it peace.


 
2blu52 
"17th Year" Silver Supporting Member
Posts: 18474
2blu52
Age: 84
Loc: Montana
Reg: 03-12-02
01-30-16 09:06 PM - Post#2605564    
    In response to Hugh in NC

Never had it with a single exhaust but with duals I had it with glass packs and when I changed to Turbos, it was less noisy but at 60 (3:55 rear gears)with the turbos it comes upwith a sound that is a result of the harmonics. I drive 55 now!!

"PEACE IS THAT GLORIUS MOMENT IN HISTORY WHEN EVERY ONE STANDS AROUND RELOADING"

THOMAS JEFFERSON


 
Bel Air kiwi 
"3rd Year" Silver Supporting Member
Posts: 4256
Bel Air kiwi
Loc: New Zealand
Reg: 04-24-14
01-31-16 03:17 AM - Post#2605582    
    In response to 2blu52

Hi 2blu52, That's one of two answers to change the harmonics. IE. change revs but usually they are only annoying because that's a speed you need to stay at constantly, if it happens at a rev range you pass through its much less obvious.
The other is change the harmonics, which is why I was asking if it was mounted very rigidly as that can amplify issues.
Basically the exhaust on these is like a great big Alpine Horn the Swiss, or some other folk play in the mountains, that stretches from the mouth to the ground. They can't change length like a trombone so they have a fairly low tone range and only work when you blow right. Ie certain revs.
All you need to do to move the frequency at which it occurs is change the overall length of the pipe or the area of sections of the system.
Unfortunately adding two feet to the tailpipe might make it sound like Barry White, but you will sound like Barry Gibbs when you walk into it. Cutting it short is very likely to explode your fuel tank and you will sound like one of the other Gibbs brothers
Stepping up the tailpipe will actually change the tone but not so much when it occurs.
If the car has always done this then something about the Pipe or Muffler is not quite stock, as we always put the frequency point somewhere other than speed limits. If its getting worse it is most likely internal to the muffler. And that fix is obvious. (Belt the can with a hammer either side of the spot welds to tighten the tin onto the baffles - too red neck for you then go buy a new one.)
The other correct fix is to fit what looks like a baby muffler somewhere easy up the pipe.
It's usually at the end of the front pipe at a convenient join.
Simply pipe cut and splice and weld or clamp. These small mufflers are actually called resonators and the reason two can systems became so much more common latter on was bigger higher compression engines and wider rev ranges which both made them necessary. All the resonator is trying to do is change the tuned length; it may make it a bit quieter also, but that depends on how its made.
Resonators can be as short as a foot long and only need to be a few inches in diameter. Unless you were a very bad person in a previous life its extremely unlikely you will change it and end up with the same sound, but if you did, it simply means you have gone from one order of harmonics to the next. There is a fix for that but it's very unlikely you will need it.
Cheers Kiwi


48 3100 RHD, 51 Deluxe 4DR RHD, 51 Bel Air parts car, 52 Bel Air P-Glide LHD. Others 23T, 32 Tudor, 58 Edsel pacer 4DR HDT, 79 F250 351C RHD. 69,70,82 Capri. No mobile, no TV, and no Jap cars.

And when it was laid to waste, they called it peace.


 
2blu52 
"17th Year" Silver Supporting Member
Posts: 18474
2blu52
Age: 84
Loc: Montana
Reg: 03-12-02
01-31-16 06:53 AM - Post#2605600    
    In response to Bel Air kiwi

Thanks KIWI, I am aware of some of this. In the 50s we always put the mufflers as far forward as we could making for a longer tail pipe and a change in sound. I have also put the tail pipes out the side in front of the rear wheels. At 82 I am not inclined to want to spend a lot of timeon my back under the car but next week I am going to change rear shocks and will take a look at the exhaust system. I purchased a kit with cast iron headers and have spent over 500 bucks rebending pipes, rehanging pipes, and correcting carb heating problems. Running the way I want it to now and can even talk to the wife going down the road.

"PEACE IS THAT GLORIUS MOMENT IN HISTORY WHEN EVERY ONE STANDS AROUND RELOADING"

THOMAS JEFFERSON


 
lilredfifty 
Forum Newbie
Posts: 5

Reg: 06-20-13
01-31-16 05:47 PM - Post#2605732    
    In response to 2blu52

Hey Hugh, research "Stop the Drone-Helmholtz Style"
I had a pickup I could not stand to drive because of the drone at 55mph. I did it myself and it made all the difference in the world. It's almost to quiet now. It's a "dummy pipe" welded onto your current exhaust and capped off. The sound waves go in and come back out and cancel the drone. It sounds crazy but it works.



Edited by lilredfifty on 01-31-16 06:02 PM. Reason for edit: No reason given.

 
Bel Air kiwi 
"3rd Year" Silver Supporting Member
Posts: 4256
Bel Air kiwi
Loc: New Zealand
Reg: 04-24-14
01-31-16 09:27 PM - Post#2605791    
    In response to lilredfifty

Hi 2Blue52, Is that being able to talk to the wife a plus or minus, just curious?
The other posters reference to Helmholtz Resonators is entirely valid and they are in common use in main mufflers. But they are tuned so really only the solution of choice for OE or volume manufacturing.
In the one off situation the usual answer is to cut in and fix a non-Helmholtz type resonator which is usually just a little straight through perforated tube type with baffling Glass or Steel wool.
Cheers Kiwi

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Attachment: 141483620.jpg (73.77 KB) 21 View(s)




48 3100 RHD, 51 Deluxe 4DR RHD, 51 Bel Air parts car, 52 Bel Air P-Glide LHD. Others 23T, 32 Tudor, 58 Edsel pacer 4DR HDT, 79 F250 351C RHD. 69,70,82 Capri. No mobile, no TV, and no Jap cars.

And when it was laid to waste, they called it peace.


 
Bel Air kiwi 
"3rd Year" Silver Supporting Member
Posts: 4256
Bel Air kiwi
Loc: New Zealand
Reg: 04-24-14
01-31-16 09:51 PM - Post#2605797    
    In response to 2blu52

Hey Hugh, You didn't do this one did you? Actually I give you far more credit than that. The only fix for a Subaru's engine noise is napalm and lots of it.
If you are going to do a weld in short resonator this style has less problems with the ends than an old school lock and rolled seam can one like a Smithy, cause they break out the ends far too easy in long run pipes.
We only made lock and roll seam ones so we put a conical brace on each end for OE use and after wards just stitch welded it as it was always oriented the correct way plus we had them by the sack full as the tooling was from something else.
Cheers Kiwi

Attachment: maxresdefault.jpg (219.33 KB) 22 View(s)




48 3100 RHD, 51 Deluxe 4DR RHD, 51 Bel Air parts car, 52 Bel Air P-Glide LHD. Others 23T, 32 Tudor, 58 Edsel pacer 4DR HDT, 79 F250 351C RHD. 69,70,82 Capri. No mobile, no TV, and no Jap cars.

And when it was laid to waste, they called it peace.


 
2blu52 
"17th Year" Silver Supporting Member
Posts: 18474
2blu52
Age: 84
Loc: Montana
Reg: 03-12-02
02-01-16 06:36 AM - Post#2605843    
    In response to Bel Air kiwi

Now this may sound strange, but after 64 years (includes dating) we still have a lot to say to each other. The lady has supported me through 4 cancers, 2 heart attacks and is one of the best dirt bike riders around. How can you beat that!

"PEACE IS THAT GLORIUS MOMENT IN HISTORY WHEN EVERY ONE STANDS AROUND RELOADING"

THOMAS JEFFERSON


 
one4dad 
"5th Year" Silver Supporting Member
Posts: 1420
one4dad
Age: 75
Loc: Baton Rouge La
Reg: 01-17-10
02-01-16 07:32 AM - Post#2605858    
    In response to 2blu52

You can't congratulations on finding the "right one". My right one went to be with the Lord 15 years ago, still miss her.

Keep talking, Bill

Bill Wilson 50 styleline deluxe 2 door sold,- 51 styleline Deluxe 2 door ,'56 235 with dual carter webers on an Offenhauser intake, Fenton headers, 56 chevy rear end and 700R4 transmission.


 
Bel Air kiwi 
"3rd Year" Silver Supporting Member
Posts: 4256
Bel Air kiwi
Loc: New Zealand
Reg: 04-24-14
02-01-16 01:14 PM - Post#2605963    
    In response to 2blu52

Hi Guys, Glad to hear it, living proof that Angels walk among Us, Cheers Kiwi

48 3100 RHD, 51 Deluxe 4DR RHD, 51 Bel Air parts car, 52 Bel Air P-Glide LHD. Others 23T, 32 Tudor, 58 Edsel pacer 4DR HDT, 79 F250 351C RHD. 69,70,82 Capri. No mobile, no TV, and no Jap cars.

And when it was laid to waste, they called it peace.


 
Hugh in NC 
Contributor
Posts: 152
Hugh in NC
Loc: In my Recliner Rockingham...
Reg: 08-01-12
02-26-16 06:12 PM - Post#2611693    
    In response to Hugh in NC

The DRONE is GONE. Sorry for taking so long to get back with the solution. I was helping a friend do several small projects on his '55 Chevy. A 4 day job turned into a 4 week job. His '55 fought us all the way, but we won.

Now, back to my '51. Everything in the exhaust system looked good and stock except for the muffler. It was a 14 inch oval muffler. I ordered a 20 inch round stock muffler from the Filling Station. Got it on today and down the street we went. No 50 mph drone. My muffler man was concerned that the stock muffler would be much louder that the offset oval muffler. You can see straight thru the stock round muffler. When revved up sitting still the exhaust has a slightly "crisper" sound, but going down the road it is very quiet. I guess that the difference in construction and length was causing the drone. GM knew what they were doing when they designed the exhaust. Thanks for all the replies.

Hugh

Here is the old muffler.


Miss Daisy - 1951 Styleline Deluxe 2 Door Sedan



 
pearljam724 
Contributor
Posts: 761
pearljam724
Age: 42
Loc: SW Pennsylvania
Reg: 01-27-14
02-26-16 06:51 PM - Post#2611702    
    In response to Hugh in NC

Very funny, you mentioned this. I started my car today, for the first time in a few months. Without a doubt, I noticed a droning sound as well coming from the end of the tail pipe. No doubt it wasn't there before, no doubt I noticed it today. I too have stock exhaust, muffler, etc. My muffler is within a year old and several hundred miles. Only thing I could gather, is packing could be starting or has worked loose. A friend called me in amazement one day, describing what he said looked like horse hair dragging from his brand new vehicles tailpipe, dragging on the ground behind it. Went over to see what the hell he was talking about, it was fiberglass packing that worked its way out of the muffler. Funny, to see.

http://i420.photobucket.com/albums/pp282/pearljam 7...


Edited by pearljam724 on 02-26-16 06:52 PM. Reason for edit: No reason given.

 
G. Baker 
Forum Newbie
Posts: 27

Loc: Ontario Canada
Reg: 12-18-15
12-05-17 05:15 PM - Post#2716986    
    In response to 2blu52

Highest Praise for getting and keeping the right one.
I suggest you do away with any resonator, put on a stock factory oval muffler and change out all the rubber mounting brackets which may have become hardened over the years. You should have an Inch of clearance everywhere.
Also make sure all windows are up. I get unbelievable resonance in my 2013 Acadia Denali if one of the windows is down slightly. Good Luck and HI to the lucky Mrs. It takes 2..........



Edited by G. Baker on 12-05-17 05:17 PM. Reason for edit: No reason given.

 
Bel Air kiwi 
"3rd Year" Silver Supporting Member
Posts: 4256
Bel Air kiwi
Loc: New Zealand
Reg: 04-24-14
12-05-17 09:45 PM - Post#2717018    
    In response to G. Baker

Hi G? How come you don't like resonators. I know the stock system is adequate and period correct but there is potential to make them quieter if you want.
Anything with a packed interior or steel internals will degrade quite quickly, particularly if not used very often.

If you go to the trouble of redoing the floor with Dynamat etc then you can also make the car run and sound better, whichever direction your sound preference, with some modern tricks.
You can also make them so they don't rot out quickly.

Cheers Kiwi


48 3100 RHD, 51 Deluxe 4DR RHD, 51 Bel Air parts car, 52 Bel Air P-Glide LHD. Others 23T, 32 Tudor, 58 Edsel pacer 4DR HDT, 79 F250 351C RHD. 69,70,82 Capri. No mobile, no TV, and no Jap cars.

And when it was laid to waste, they called it peace.


 

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