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PostPosted: Thu Mar 14, 2019 6:09 am 
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Location: Raleigh, NC
Thank to all for some very good information. Turns out we are also replacing the exhaust in our vintage MGB so this is great info.

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PostPosted: Thu Mar 14, 2019 9:38 am 
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Joined: Fri Aug 12, 2011 4:03 pm
Posts: 207
Location: Northeast PA
DavidBednarz wrote:
jimmypet wrote:
Mine was an Oval "Dynomax Performance 33274"

There is a picture of the Walker post race / failure on my Instagram: https://www.instagram.com/p/BKD75E0hLKS/

I posted a picture of the Hooker as well, that failed much more spectacularly: https://www.instagram.com/p/BJJIgvtBMzv/

I have a Dynomax bullet on my other race car and it is pretty much indestructable,,, but its also too loud. I wanted a quieter option.
The Hooker Max Flow that I had was perfect for years until if finally failed.
The Walker sounded great, but failed really fast.
As I posted the Flowmaster 40 series race muffler thats in the car now is living on pretty well at a pretty decent volume level.

Cheers
jimmy p



Thanks for sharing the photos. The part number should be 17xxx or 24xxx. It appears to be an Ultraflow welded, that failed by the shell emboss. The shells thin slightly from the "lettering" emboss, and this becomes the weakest point. I have experienced this myself.

Round shapes have higher natural frequencies than oval shapes, and are more durable for this reason. Rounds are also more durable from impacts for the same reason. Production engines that rev to 9K RPM create strong pulses. This assumes you have the package space to fit the round that you need. Oval mufflers exist so you can get more muffler volume in a flatter space, with some risk too.

I assume your exhaust pipes are likely in the 2.25 or 2.5" range. The mufflers I suggest for your application:

Dynomax 17230 6" round 2.5 inch pipe - most volume = most sound control - if you can fit a 6" round
Dynomax 24215 or 24236 4" round 2.5 inch pipe - if you can only fit a 4" round
Dynomax 24244 5" round 2.25 inch pipe. - in the middle for muffler size. I personally use this one.


Thank you for the thoughtful reply David. I took that part number from the Summit invoice, I guess thats their internal part number.
That failed muffler (as well as all the others I noted) were all 3" in / out centered.

So far I am doing well with the current Flowmaster in place, its reasonably quiet and seems to be holding up very well.
Thanks for your advice on round versions. Thats great information.

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PostPosted: Thu Mar 14, 2019 9:57 am 
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Joined: Wed Oct 28, 2009 9:24 am
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I use the 24244 Dynomax muffler on my Scirocco - light, inexpensive and great sound reduction. As is my habit I invested a ridiculous amount of research to find a good light muffler that was inexpensive. The cylindrical 5" can on this muffler provided more than twice the packing volume of my previous 4" drawn tapered "bullet" muffler and took ~10dBA off the sound reading!

Note - the pics on Jegs and Summit of the 24244 muffler are wrong and show a "bullet" shape. Amazon shows it correctly.

I don't think anyone has addressed diameter of pipe - I have no hard facts but 2" sounds a bit small for a race 1.8 liter. Header collector diameter may be a factor of course.

Al


Last edited by Al Seim on Thu Mar 14, 2019 10:09 am, edited 2 times in total.

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PostPosted: Thu Mar 14, 2019 10:00 am 
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Location: Raleigh, NC
Al:

You are correct. I am looking at 2 1/4 or 2 1/2 ID systems. Just need a new collector.

Rick

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PostPosted: Wed Mar 20, 2019 7:09 am 
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Joined: Sun Nov 01, 2015 10:21 am
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Location: North Florida
The Maniflow race header I bought from APT has a 2" OD collector.


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PostPosted: Wed Mar 20, 2019 7:32 am 
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Location: Raleigh, NC
Jacko:

My Maniflow does as well. Recent engine dyno work by the vintage MGB team suggests that 2 1/4 is the better way to go.

Rick

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PostPosted: Wed Mar 20, 2019 12:29 pm 
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Location: North Florida
My engine is going to be pretty mild, so I think I will try to get by with this, budget is tight.


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PostPosted: Wed Mar 20, 2019 2:18 pm 
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Joined: Wed Jul 06, 2011 3:48 am
Posts: 590
Location: Florida
Ran a Maniflow for years on our 1275s. Rearranged the molecules to run through the tunnel and it still works great. Nice piece. Do remember the 18" for the tubes if you modify one for the A series engines.

Bob

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