Spiral mufflers anyone?



Spiral mufflers anyone?

Postby NOT A TA » May 14th, 2014, 10:28 pm

I'm looking for mufflers to use in my NOS Pontiac Hooker side pipes. The ones that came stock with the pipes look too restrictive. I'm considering Spiral mufflers from Spiral Turbo Specialties. Any thoughts or opinions welcome. http://www.spiralturbobaffles.com/index.html

Here's the side pipe setup I'll be using. And pic below of the stock mufflers.

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Re: Spiral mufflers anyone?

Postby 87vette81big » May 15th, 2014, 7:06 am

Your 1970 Bird will run best with No Mufflers.
Just Straight Headers & Open Side Pipes.
Wait for Grumpy, He knows what to use on BBC Sidepiped C3 Corvettes.

Pontiacs Set in all out Race Trim run best with 2"-2-1/4" Primary Header Tubes, 28"-32" Long, 3-1/2"-5" Collectpr.
True 3"-5" Mandrel bent exhaust.

I want 4" inch on mt 70 TA Eventual. 3" on now.
5" Can be done but it would have to dump right before the rear axle & 5" Turndowns.

1-7/8" D-port Header primary tubes are smallest acceptable I have found for 400-455. Ponchos.
Still allow WOT 7,000 RPM Pull in 4th gear.

Pontiac V8 engines hate restritive exhaust systems.

If non side pipe layout, The MOROSO Spiral Race Mufflers an excellent choice.
Last edited by 87vette81big on May 15th, 2014, 7:09 am, edited 1 time in total.
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Re: Spiral mufflers anyone?

Postby 87vette81big » May 15th, 2014, 7:08 am

The BORLA XR Race 4" In & Out Are killer nice.
Support 1500+ HP 5.0 Renegade Chi town racers tell me.
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Re: Spiral mufflers anyone?

Postby grumpyvette » May 15th, 2014, 10:05 am

if you measure that insert muffler it quickly becomes obvious that the internal baffles are highly restrictive too flow and just one look at that internal feed pipe being about 1.6" in diam can,t help but strangle the high rpm exhaust flow
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theses at least a dozen different muffle insert designs available, most are effective at reducing sound levels but most also restrict exhaust flow rates in the upper rpms making the power seem to hit a wall at some rpm level obviously dependent on several factors like cam, gearing engine displacement etc, most cars have an obvious power improvement if you remove the muffler inserts at the track.


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heres where some welding skill , owning a decent welder and having a willingness to think , research a bit and fabricate makes custom work on an exhaust well worth doing, all the commercial muffler inserts Ive seen are rather restrictive, Ive seen dyno chart results in the past where the difference was over a 50 hp reduction at peak power between the open headers, exiting into open side pipes on a corvette and the the same corvettes engine run with inserts, inserted.
I know when I had my 496 big block , I had hooker side pipe headers installed , we noticed a big difference in MPH with the inserts in place (something like a 3mph reduction) so we simply cut about 12 3.9" diam. circular baffles out of perforated sheet
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and spaced then with a threaded rod and 24 nuts and washers spaced about every 3" on a 3 foot long section of 1/2" threaded rod, and inserted them in each side pipe ,this perforated sheet we used had about 1/4" holes and about 50% coverage ,and worked reasonably well,at reducing the noise compared to open headers,and allowed us to make decent power , much better than the hooker inserts did, but the insert we made was not as well designed as i would make now, as back then, I had far less understanding of what we were really trying to accomplish, but still it worked.

IF YOU HAVE A DECENT MIG OR TIG WELDER and access to some metal fabrication equipment I think youll be far ahead if you take the time and effort to use perforated steel sheet and tube or pipe too custom build side pipe insert mufflers, similar to the spiralturbobaffles out of perforated steel sheet and steel tube, as the perforated steel tube and sheet material lends it self quite well to the application while allowing both good flow rates and good sound wave disruption, a custom pattern made from cardboard, for the baffles and the perforated central 1"-1.5" pipe would not be dirt cheap but would be available if you shop carefully and flow better than the spiralturbobaffles
theres also exhaust insert cones whose total open surface area exceeds the diameter , because the geometry of the surface area of a cone allows a greater surface area on the surface than the base but I think the smallest is 3" diam. that you can fabricate if you weld, these are expensive if you buy them but hardly difficult to fabricate

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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: Spiral mufflers anyone?

Postby grumpyvette » February 16th, 2015, 5:19 pm

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: Spiral mufflers anyone?

Postby NOT A TA » February 17th, 2015, 11:23 am

The laminar flow type muffler that combines 2 of the cones looks like something I could fabricate without spending too much time. This may be an option for me and help me save some money so I can get the car finished quicker.
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