Cabin drumming with extractors vs iron manifold

[bigmal 225]

Question re cabin drumming. I have iron manifolds with 2 1/4" pipes and balance tube on my 351 Cleveland. There is a bit of drumming when going up hills.

I am thinking of going with extractors. Has anyone gone down this path and noticed the difference to drumming? Is it likely to get worse, reduce, or stay the same.

I like loud, but drumming is annoying.

Thanks,

 

[Shep69 149]

When I’m cruising around Mal I find it ok but at idle it’s sometimes a bit annoying. I run extractors. Could be to do with resonance frequency at idle rpm though. 

[unilec 57]

Mal, sounds like you have exhaust drone issues. You can fit "J" pipes to your exhaust to help eliminate this problem, unfortunately you need to know where to fit them and the correct length, but worth doing some research into.Do you have a "X" or "H" pipe joining both exhausts together?

[Mach1 Driver 560]

You may need 1/4 wave resonance tubes to kill the drone. There's a good post on VMF. Search for "Drone help" and see post #3 for the formula. A resonance tube is a specific length of exhaust pipe added behind the muffler. It branches off of the existing exhaust pipe and is a dead end. You calculate the length of pipe you need based on the speed the drone occurs. The sound wave zips down the pipe, bounces off the end and returns to the main pipe at exactly the same time that the next sound wave is coming down the pipe and they cancel each other out. Pretty nifty. We used to do the same thing to cancel out microwaves in microwave oven door seals- its the same principal and is called a 1/4 wave choke. Don't worry, its simple math and any good muffler shop can do it.

[1969_Mach1 333]

What type of mufflers are you using?  Chambered mufflers, especially the small two chamber mufflers tend to cause resonating inside the cabin (more interior noise).  Flowmaster's Delta Flow design chambered mufflers are a little better (less interior noise) than the non Delta Flow chambered mufflers with regards to resonating inside the cabin.

[barnett468 418]

Headers will have zero affect on "drone", but they will add a LOT of additional noise to the cabin.

"Resonators will not eliminate drone in a car that has chambered mufflers like typical flowmasters, which are the ultimate in drone, but it will reduce it if they are the correct size etc.

 

 

[bigmal 225]

Thanks for the suggestions. As I would like to fit extractors I just wanted to see if the drone would be affected. I don't mind if the exhaust is louder (prefer) but I just don't want to increase the drone. I added the pictures so you can see what I have now.

[1969_Mach1 333]

Are those basic old school turbo style mufflers?  If so, those are some of the more quite design for both interior and exterior noise.  Is your exhaust well insulated from the car at the hangers so vibrations are not transmitted into the car?

Barnett468 is right, headers will increase exhaust noise a lot to the interior of a car.  Shorty headers are not as bad as full length headers.

[bigmal 225]

4 hours ago, 1969_Mach1 said:

Are those basic old school turbo style mufflers?  If so, those are some of the more quite design for both interior and exterior noise.  Is your exhaust well insulated from the car at the hangers so vibrations are not transmitted into the car?

Barnett468 is right, headers will increase exhaust noise a lot to the interior of a car.  Shorty headers are not as bad as full length headers.

Not sure about the design of the mufflers. The hangers are rubber insulated and I have resomat throughout. The headers I am looking at are basic design for an Australian Falcon. They will need to be modified to fir with the RRS steering rack. Not a lot of options with the limited clearance.

[1969_Mach1 333]

I missed the fact you currently have stock cast iron exhaust manifolds installed.  With those mufflers and stock exhaust manifolds I'd think the exhaust note is fairly quite. Is the motor stock or does it have an aggressive cam with early exhaust valve opening?  More aggressive cams increase exhaust noise.  As exhaust valves open earlier more of the combustion explosion is heard through the exhaust.

[bigmal 225]

30 minutes ago, 1969_Mach1 said:

I missed the fact you currently have stock cast iron exhaust manifolds installed.  With those mufflers and stock exhaust manifolds I'd think the exhaust note is fairly quite. Is the motor stock or does it have an aggressive cam with early exhaust valve opening?  More aggressive cams increase exhaust noise.  As exhaust valves open earlier more of the combustion explosion is heard through the exhaust.

Hi, I am not to knowledgeable on cams so have attached the details. A little choppy at idle but not too much. Has a 600 Holley but that's about it. FMX and 3.25.

[barnett468 418]

5 hours ago, bigmal said:

Not sure about the design of the mufflers.

It looks like there is lettering on the bottom of the mufflers, if so, what are the letters?

[aslanefe 333]

One of my cars with chambered mufflers, I wrapped fiberglass insulation around the muffler which reduced the drone and interior noise.

[bigmal 225]

17 hours ago, barnett468 said:

It looks like there is lettering on the bottom of the mufflers, if so, what are the letters?

Not sure. I will need to get under there on the weekend.