B-body Hemi mufflers performance vs. aftermarket

Posted By: 6PAX

B-body Hemi mufflers performance vs. aftermarket - 02/17/09 01:42 AM

Does anyone know how reproduction 68-70 style B-body Hemi mufflers compare performance-wise to aftermarket mufflers like Flowmaster three chamber mufflers (mufflers that are similar in width and length)?

Posted By: amixon

Re: B-body Hemi mufflers performance vs. aftermarket - 02/17/09 12:10 PM

I have to take a stab at this, you mean the original 1968 style mufflers? I would say the restriction would be very high and the flow capacity of the factory style stuff would be very low. Scotty Brown used to have a flow chart with that stuff up there, but I can not locate anything similar to that today.

I did find this little site it has some information on flow testing but they only go up to a 2.5 pipe size...hope it helps some

http://www.broaderperformance.com/muffler_flow_tests.htm

I liked the sound quality of the DynaMax, they tend not to drone like the Flowmasters and such.

What is it you are looking to do?

Posted By: 6PAX

Re: B-body Hemi mufflers performance vs. aftermarket - 02/17/09 04:16 PM

I am going to be buying some mufflers for my car and I don't want anything loud but I do want the best performance I can get at the same time. I like the sound of hemi mufflers like those on my 70 GTX so if their performance compared to whatever the quietest aftermsrket performance mufflers are wasn't that much different, I would go that route. If there is a significant difference I will go with whatever the quietest aftermarket performance mufflers are that are available.

Posted By: None2Slow

Re: B-body Hemi mufflers performance vs. aftermarket - 02/17/09 05:53 PM

Borla, Dynomax and Magnaflow all sound nice, depending on what you get, but sound is in the ear of the beholder.

Posted By: DPelletier

Re: B-body Hemi mufflers performance vs. aftermarket - 02/18/09 12:24 AM

Many of the top runners at the Pure Stock drags ( www.purestockdrags.com ) use Walker/Dynamax Ultra Flows so I ordered a set of 2 1/2" Ultra Flows to go with my 2 1/2" mandrel bent TTI exhaust system. The Ultra flows perform very similar to the Hooker Max Flows in the chart posted above. This isn't surprising as they share the straight-through design.

The stainless ultraflows are crimped similar to the stock mufflers. They are also available in aluminized versions, but then they use welded construction. You won't fool anybody into thinking the s/s ultraflows are NOS mufflers, but if you turn them so the stamped "dynomax" logo is facing the floorboards, then they look semi-correct.

I'm told they are fairly quiet, but I haven't fired mine up yet. If you want something that looks sorta stock, but performs way better then I would recommend the ultra flows. They are a little pricey, though.

http://www.dynomax.com/products/ultrafloss.html

Dave

Posted By: gch

Re: B-body Hemi mufflers performance vs. aftermarket - 02/18/09 02:47 AM

Check with accurate ltd.I believe he produces resto correct "hemi" mufflers with stock and improved flow as well.

Posted By: minivan

Re: B-body Hemi mufflers performance vs. aftermarket - 02/18/09 05:20 PM

Quote:

Check with accurate ltd.I believe he produces resto correct "hemi" mufflers with stock and improved flow as well.

I have Accurates "improved flow" hemi mufflers on my 67 coronet with a 440.. Just a little louder than stock..

Posted By: BELVEDERE67

Re: B-body Hemi mufflers performance vs. aftermarket - 02/18/09 08:06 PM

I'll add my

here. On a mildly built motor, Dynomax ultraflows would be faily quiet. But on a modified motor,they are quiet at idle but not at WOT. I love my ultraflows but with mine, x pipe installed, they are not quiet. In my mind, they are perfect. I love the sound, but quiet it really isn't. If you drive it like you stole it, you may want something else. Just trying to be fair here. I'd do mine the same all over again tho.
There have been threads with sound bytes previously. You may want to check the archives.

Posted By: Tom Hand

Re: B-body Hemi mufflers performance vs. aftermarket - 02/18/09 09:20 PM

Here are typical after market replacement HEMI-sized mufflers.

Attached File

5035334-2.5muffdata.xls (452 downloads)

Posted By: Tom Hand

Re: B-body Hemi mufflers performance vs. aftermarket - 02/18/09 09:24 PM

Look at the stockers in the lower section of this chart. 21848 is the HEMI sized muffler. The ones from Waldron and others will flow better but this data will give you an idea of the stock replacements and how they react.

Note something else: it is easy to see why the old Corvair turbo muffler worked, in fact, they flow about the same as today's leading chambered muffler with significantly less sound levels.

Attached File

5035345-3muffdata.xls (381 downloads)

Posted By: DPelletier

Re: B-body Hemi mufflers performance vs. aftermarket - 02/19/09 12:12 AM

WOW, thanks for the great info!

I'm even happier with my Ultra flow decision based on that info.

Cheers,
Dave

Posted By: Streetwize

Re: B-body Hemi mufflers performance vs. aftermarket - 02/19/09 12:24 AM

Ultraflows can be fairly mellow at idle on milder motors without a lot of compression and especially without a lot of cam overlap. When you go big cubes, high compression and long duration they tend to get a bit louder.

I went with the Dynomax Hemi Mufflers because with big cubes, 12:1 and a big cam I felt the Ultraflows would be a "touch too much" for the neighborhood and town I live in. The Hemis are 3" all the way through and flow well, at least on par with the shorties. I believe the OEM style Hemi's are 2 1/2 to 2 1/4 ID, but I believe Accurate may make a 3" internal.

Here's a sound clip with 3" dmax Hemis:

http://www.youtube.com/watch?v=jd8GeXYYkKU&feature=channel_page

Posted By: DPelletier

Re: B-body Hemi mufflers performance vs. aftermarket - 02/19/09 12:31 AM

Quote:

Ultraflows can be fairly mellow at idle on milder motors without a lot of compression and especially without a lot of cam overlap. When you go big cubes, high compression and long duration they tend to get a bit louder.

I went with the Dynomax Hemi Mufflers because with big cubes, 12:1 and a big cam I felt the Ultraflows would be a "touch too much" for the neighborhood and town I live in. The Hemis are 3" all the way through and flow well, at least on par with the shorties. I believe the OEM style Hemi's are 2 1/2 to 2 1/4 ID, but I believe Accurate may make a 3" internal.

Here's a sound clip with 3" dmax Hemis:

http://www.youtube.com/watch?v=jd8GeXYYkKU&feature=channel_page

That sounds great!

I was going by what the other guys with similar setups were saying; 440, 10.75:1, stock(ish) legal cam, iron manifolds = fairly quiet, esp. at idle.

If not......the only neighbors I have are deer!

Cheers,
Dave

Posted By: patrick

Re: B-body Hemi mufflers performance vs. aftermarket - 02/19/09 01:51 PM

Quote:

Ultraflows can be fairly mellow at idle on milder motors without a lot of compression and especially without a lot of cam overlap. When you go big cubes, high compression and long duration they tend to get a bit louder.

I went with the Dynomax Hemi Mufflers because with big cubes, 12:1 and a big cam I felt the Ultraflows would be a "touch too much" for the neighborhood and town I live in. The Hemis are 3" all the way through and flow well, at least on par with the shorties. I believe the OEM style
Hemi's are 2 1/2 to 2 1/4 ID, but I believe Accurate may make a 3" internal.

Here's a sound clip with 3" dmax Hemis:

http://www.youtube.com/watch?v=jd8GeXYYkKU&feature=channel_page

those are the dynomax 17769's I presume? the large body ones? I have one in a big single config on my 5th ave with a dynomax race bullet in the tail and it's not bad.

if you are looking for a little quieter or don't need the 3" straight through, the 17748 & 49's are the 2.5" version.

adding the race bullet in my tail as a resonator made a big difference in knocking the noise level down, especially in the interior of the car.

Posted By: ademon

Re: B-body Hemi mufflers performance vs. aftermarket - 02/19/09 03:37 PM

I went with the dynomax large body hemi muffler, also used a pair of magnaflo 4" round by 24" resonators/mufflers right before the tips, they look like the stock resonators used on hemis from the rear, nice and quiet! can hear the carb suck air when you stand on it!