At My Wits End With The Drone/Resonating!!

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Ehbody

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This should probably be in the "exhaust"section,but I'm hoping for more advice in "general". I have a "70 Duster 340 with edelbrock RPM Performer cam and heads, 10:5 compression, 650 thunder carb,833 4spd.O/D(cast housing, 3.91 Suregrip... and some other goodies.The computer program says I should be about 425HP.(haven't dynoed it yet). I'm using stock HP exhaust manifolds(I like the stock look) and dual 2 1/2" H pipes. I get a horrible drone around 2000-2400 rpm (I can't just stay out of that range as it is where the engine runs when I'm on the highway).I started with "FloPro" Super V's(similar to Flowmaster),then tryed "FloPro" Maxes(similar to Magnaflow...droned,but almost go quiet after 2400 rpm...weird). I've read the threads in the exhaust section...alot of people say that the Dynomax Superturbo's don't drone...I tryed them and the drone is just as bad as the Super V's:banghead:.I like a rumble at idle and when accelerating,but not at a constant cruise speed. Do I go back to the Maxes and put on resonators? Do I need to go "stockish"(although I don't want to constrict the system).I can't keep changing mufflers...please help. Thanks, Dan
 
you have the same combo i have as far as motor carb gears. i have 21/2 inch flowmasters with headers and no h pipe. mine is loud when you put your foot into to it but not to bad when cruising. you can always turn up the stereo. I had a kind of drone or maybe more of a vibration before i had the engine balanced. but it is way better since balancing the motor. good luck . oh yeah maybe a 323 gear would help at cruising speed.
 
EH, I would hate for you to spend your hard earned money crutching your system with add on resonators. If it were me, I'd go buy some Dynomax VTs and they will take care of the drone. I have two 2.5" ones here I'd sell but with shipping cheap from Summit, you can likely get them cheaper where you are. Mine we too quiet on guy's 383;they are essentially brand new and ready to run.

Truly, the VT's will take care of almost all the drone you have from 2000 to 2350 rpms. The ones on my brother-in-law's 12 second 360 68 Cuda are very quiet at idle and light throttle and then open up to sound powerful at WOT. They have zero resonation.

Tom Hand
 
Ehbody said:
This should probably be in the "exhaust"section,but I'm hoping for more advice in "general". I have a "70 Duster 340 with edelbrock RPM Performer cam and heads, 10:5 compression, 650 thunder carb,833 4spd.O/D(cast housing, 3.91 Suregrip... and some other goodies.The computer program says I should be about 425HP.(haven't dynoed it yet). I'm using stock HP exhaust manifolds(I like the stock look) and dual 2 1/2" H pipes. I get a horrible drone around 2000-2400 rpm (I can't just stay out of that range as it is where the engine runs when I'm on the highway).I started with "FloPro" Super V's(similar to Flowmaster),then tryed "FloPro" Maxes(similar to Magnaflow...droned,but almost go quiet after 2400 rpm...weird). I've read the threads in the exhaust section...alot of people say that the Dynomax Superturbo's don't drone...I tryed them and the drone is just as bad as the Super V's:banghead:.I like a rumble at idle and when accelerating,but not at a constant cruise speed. Do I go back to the Maxes and put on resonators? Do I need to go "stockish"(although I don't want to constrict the system).I can't keep changing mufflers...please help. Thanks, Dan
Click to expand...

How do you have the exhaust exiting car?

Troy
 
69340 said:
you have the same combo i have as far as motor carb gears. i have 21/2 inch flowmasters with headers and no h pipe. mine is loud when you put your foot into to it but not to bad when cruising. you can always turn up the stereo. I had a kind of drone or maybe more of a vibration before i had the engine balanced. but it is way better since balancing the motor. good luck . oh yeah maybe a 323 gear would help at cruising speed.
Click to expand...
I have Overdrive...3.23 gears would drop my rpm's too low for my liking...as it is I'm only 2300 rpm @60 mph. I like the rpm...just not the drone. As far as turning up the stereo,it would have to be pretty loud(my wife wears ear plugs when we are in the drone range). Dan
 
VOETOM said:
EH, I would hate for you to spend your hard earned money crutching your system with add on resonators. If it were me, I'd go buy some Dynomax VTs and they will take care of the drone. I have two 2.5" ones here I'd sell but with shipping cheap from Summit, you can likely get them cheaper where you are. Mine we too quiet on guy's 383;they are essentially brand new and ready to run.

Truly, the VT's will take care of almost all the drone you have from 2000 to 2350 rpms. The ones on my brother-in-law's 12 second 360 68 Cuda are very quiet at idle and light throttle and then open up to sound powerful at WOT. They have zero resonation.

Tom Hand
Click to expand...
I thought of them,but some folks are complaining about rattling inside the mufflers. Dan
 
Aves said:
How do you have the exhaust exiting car?

Troy
Click to expand...
About an inch rear of the bumper...I've read that exiting under the car causes drone( before I installed the exhaust),so I knew that wasn't going to work for me. I didn't have the H pipe installed at first ,but installed it (after trying the 2nd set of mufflers)...still didn't help much. Dan
 
Correct, some of the early ones or the lighter spring ones on larger engines had a clank at low rpm or idle but the later ones and the large spring ones work well.
They also have newer ones coming set up for really large engines with thumping cams but your set up sounds abut average to me (not saying it is low powered, just not a big thupin' window rattlin" cam 540 cu. in.)
Tom
 
had the same problem with my RR after a lot of research usually have to go with resonators just before the tips or headers, i went with resonators just like most of the 440/hemi cars had from the factory.
 

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dynomax ultraflows.i swapped my flowmasters out for these and am happy with the results.
 
Do yourself a favor and get a set of "real" Magnaflow mufflers. The best sounding and least droaning mufflers on the market. They are the only muffler we use on all of our builds.
 
The trouble with an a-body is you really can't fit the resonator on without doing some tricky fitting and adapting. It can be done , obviously, but it is tougher. :(
Tom
 
Have almost the same setup. Had the very same problem. Contacted Dynomax Mufflers and found they make mufflers with valves in them that open at full throttle and are only partially open at the 2000-2600 range which eliminated the drone altogether.
 
A340, Yep, Dynomax VT's.
 

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I posted in the exhaust section that Summitt has the VT's on sale for $85ea. Bought a set for my car but haven't installed them yet.
 
Put your car up on a lift and look over the whole exhaust system for any interference. You might have a pipe touching the chassis or a part of the suspension (rear shocks, etc.), or one of the hangers might be installed wrong.

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I have THESE mufflers (26" long "powersticks") on my '70 Duster in a 2.5" X-pipe system and got minor drone around 45 mph with 904 trans and 2.76 gears. Engine was stock 120k mile 318 shortblock with 302 heads, 4-bbl, and mild cam. It wasn't too bad because it was a very narrow RPM range where it hit (2400 I think) and giving a little more/less gas would make it go away. Highway was fine, surprisingly quiet and smooth, but I had a cruising RPM of 3000, not 2400 like you with overdrive. In the end I think it was due to the fact that the rear springs sagged and made one of the pipes contact the rear shock. If your chassis is OK you could try a pair of the short Powersticks and use them as resonators like they say on the site.
 
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