My setup: 2000 LS1 with MAC Headers/ORY, 3" Magnaflow Cat-back & a Cut-Out (Zed-Style)

Alright... 2 issues... I think I have an exhaust leak SOMEWHERE before the collector. I don't believe it is from where the headers bolt up to the head because 1. I can't hear it from in the engine bay, and 2. No obvious carbon buildup anywhere on the heads... I have checked the Y-pipe for signs of leak, but I can't find anything... the sound from outside the car is a rather obvious ticking noise, and from the inside of the car (while driving) is almost like a rushing air sound, with a little marble-in-a-can sound... almost like pining (A-TAP shows NO RETARD, so I don't think it is pinging/knock)... Any ideas on this? How would I track down an exhaust leak?

and Second, Without sacraficing too much of the VOLUME, how do I get rid of this damn MAC/ORY Rasp... I want to maintain as much of the loudness/volume to the exhaust tone (both capped and uncapped), but would like to mellow out the harshness a tad... any thoughts?

<img src="graemlins/gr_cheers.gif" border="0" alt="[cheers]" /> Thanks in advance!

 

Did you do the AIR tube restrictor mod? It's a plate that blocks the air pump check valve in that tube from fluttering with MAC headers. Sounds like you are describing that exact condition.

You could try Dynomax bullet mufflers in the ORY to lessen the rasp. Or just put some RT bullet cats in there if you have to pass emissions still.

 

Also, Mac headers have had problems in the past where the weld near the collector leaks. Thats something to check too.

 

Anyone have the link to the air restrictor mod?

 

Take some sheet metal, a pair of tin snips, a 5/16" and a 3/16" drill bit, and two sets of AIR pipe gaskets and make a pair of restrictor plates for the AIR pipe flanges where they bolt to the headers. The 3/16" restriction dampens the pulse that causes the flutter, but still allows the system to function normally and pass the OBD2 system diagnostic, meaning no SES light.

Worked for me. I got a machinist at work (I work in a refinery) to take some shim stock and we marked it off, drilled it and cut it to fit.

http://riptide63.homestead.com/restrictor.html

Les

[ December 06, 2001: Message edited by: 02 SOM WS6 ]</p>

 

If you're not **** about the looks, you can do it with some Lowe's sheetmetal and tin snips. Use a gasket as a template, cut, drill the three holes and install. I have to buy some gaskets because I reused the original ones. Not one of my better ideas...

 

A few months after doing the restrictor mod the fluttering came back. Only way to fix it for sure is to delete the whole AIR setup.

Hi Dr. Boost.

 

How does the Magnaflow sound with the cutout capped? I am thinking about going with the Magnaflow soon to replace what I have now. Just wondering how much difference you noticed with the magnaflow when you put the headers on.

GregM

 

[quote]Originally posted by JimTA:
<strong>A few months after doing the restrictor mod the fluttering came back. Only way to fix it for sure is to delete the whole AIR setup.

Hi Dr. Boost.</strong><hr></blockquote>

How is that possibile? Unless the plate that you used got damaged somehow there is really no way that it could just come back like that.

I've never heard of it coming back on anyone else's car before <img src="images/icons/confused.gif" border="0">

 

I would actually like to discuss this further. I’m planning on MACs in the near future and I’ve never heard of the restrictor mod not working/lasting. I’d like to know how many people this has happened to? This is the first case I’ve heard...

 

The Magnaflow sounds WONDERFUL... It is a nice throaty agressive sound without being obnoxious... 3" all the way back... <img src="images/icons/wink.gif" border="0">

If are in the mood for obnoxious, tnen open up the cut-out... WAAAAAY too much IMHO.

I have decided to install a total block off plate, as opposed to the restrictor plate. I plan to disconnect the hose from the air-pump BEHIND the Driver's Headlamp. It is my understanding that this will NOT throw a code... to remove the pump itself would, but to simply disconnect it from the rest of the system is fine... (I have a friend with a 99Z28 who has done this with success...) If it is the air system causing noise, this should eliminate it... Just to be safe, I am also replacing the EGR tubing assembly & gaskets to ensure that is not the root of my problem!!! <img src="images/icons/wink.gif" border="0"> Thanks for all your help.

 

I had MACS for quite a while, initially no restrictor and had the annoying clicking. I did the mod as descibed above and no more clicking. Lasted for the 8 months it was on with no problems. I came to really like the noise of the MACs but I have a Whisper Catback and it sounded a little different than some of my friends cars with MACs and other CATbacks. The only way I know of to get rid of the resonance is with a bullet style muffler after the Y comes together.
But then clearance issues erupt.

 

As for the restrictors...
I put that page together a little over a year ago after having good results experimenting with restrictors on my own car. Mine are still holding up after more than a year and 14,000 miles. I'd suggest using some reasonably thick sheet metal, as I've seen where some folks have had them burn out after a while when they used thin metal. Also, some have had to experiment with different size holes in the plates with different combos.

<img src="images/icons/smile.gif" border="0">

[ December 07, 2001: Message edited by: Riptide ]</p>

 

Bill, thanks for the info. You experiences seem to be in line with most others that I’ve talked to that have use the restrictor plate. Were you running the MACs in off-road version or with some kind of cats?

 

As far as the raspy exhaust sound goes, i installed dynomax bullet mufflers in my y pipe right behind the header on both sides. The improvment in sound was huge from this mod. It almost entirely eliminated the raspy sound. I also put a new collector on my mac y pipe. The car also didn't appear to lose any power from the install of the bullet mufflers either.

also, I installed restrictor plates on my air tubes and everythings been quiet around there ever since.

hope this helps

Jordan