Four Mufflers?
Thread Starter
Le Mans Master
Joined: Aug 2000
Posts: 6,273
Likes: 14
From: Austin TX
Four Mufflers?
Last Saturday I stopped by to see Zwedes beautiful 71 coupe with a 454. He cranked it up with a new cam and I was surprised at how quiet it was. He explained that he had 4 mufflers - 2 in the normal configuration and two glasspacks in place of the exhaust pipes between the trans cross member and the differential.
The idea is the glasspacks partially quiet things down without adding backpressure before the exhaust pulse hits the regular turbo muffler.
Seemed to be working for Zwede. Anyone else tried this? if so, what were your results?
The idea is the glasspacks partially quiet things down without adding backpressure before the exhaust pulse hits the regular turbo muffler.
Seemed to be working for Zwede. Anyone else tried this? if so, what were your results?
Drifting
Joined: Nov 2001
Posts: 1,804
Likes: 0
From: Gettin crazy with the Cheez Whiz! OK
Re: Four Mufflers? (flynhi)
Wouldn't glasspacks cause some back pressure too? It seema that any thing that causes a reduction in sound causes backpressure. If I'm mistaken somebody correct me.
Jason
Jason
Le Mans Master
Joined: Jul 1999
Posts: 9,206
Likes: 17
From: Sewell NJ
Re: Four Mufflers? (flynhi)
I'm not sure about other years but 74s came that way from the factory. Just behind the crossmember were a pair of resonators (factory term for glasspacks or expansion chambers)which then lead back to the normal mufflers. Replacement pipes do not have the resonators and just use a straight pipe back to the mufflers. If you look under a 74 you will see heat shields behind the crossmember where the resonators should be.
Le Mans Master
Joined: Nov 1999
Posts: 5,768
Likes: 3
From: San Diego CA
Re: Four Mufflers? (inferno-vette)
Never heard about glasspacks causing backpressure, after all cherry bombs are glasspacks. (the inner tube in the GP should be the same as the pipe.
Paul
Paul
The reason:
The perforated core of these mufflers have little edges protruding into the exhaust flow - to in effect catch the exhaust and force it into the fiberglass packing around the core - these little protrusions create an amazing amount of turbulance in the muffler body and hence backpressure. Cherry bombs are about the worst.
The only benefit to the glass packs is that they are loud, obviously shorter sections are less restrictive than longer ones, I would have no problem using 12" glasspacks as a resonator of sorts.
However, apart from volume, Turbo mufflers have glasspacks beat hands down.
I do not know if this applies to the newer generation of straight through, fiberglass packed mufflers such as the Ultra-flow, the edelbrock design or the Borla types. This does apply to the classic old Cherry bombs and the woody woodpecker Thrush mufflers.
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
Re: Four Mufflers? (fauxrs)
some if not most glasspacks are the most restrictive type of muffler available. A test was done a few years ago which showed that the classic glasspack design - straight through with perforated core - was much more restrictive than the classic turbo muffler.
I'm thinking about removing them and instead using the disc inserts in the header collectors. Reason is that although the bullets are only 4" diameter, they hit on big bumps.
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Melting Slicks
Joined: Feb 1999
Posts: 3,078
Likes: 1
Re: Four Mufflers? (flynhi)
A couple things.
First of all, I have a pair of turbo mufflers on a custom dual exhaust on an 86 IROC with a nonstock tuned port 355. Those mufflers are QUIET!!!
I cannot believe how silent they are. That guy literally did not need to add an extra pair of glasspacks.
I can make a good recommendation on glasspacks. I have a pair of Dynomax Ultraflows on my Shelby. They sound good without being overly loud, and they look great because they're polished. It's a straight thru design too.
[Modified by MoMo, 12:50 PM 5/30/2002]
First of all, I have a pair of turbo mufflers on a custom dual exhaust on an 86 IROC with a nonstock tuned port 355. Those mufflers are QUIET!!!
I cannot believe how silent they are. That guy literally did not need to add an extra pair of glasspacks.
I can make a good recommendation on glasspacks. I have a pair of Dynomax Ultraflows on my Shelby. They sound good without being overly loud, and they look great because they're polished. It's a straight thru design too.
[Modified by MoMo, 12:50 PM 5/30/2002]