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Old 07-10-2019, 06:41 AM
71 T/A 71 T/A is offline
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Default Quietest 2.5" Mufflers for 69 GTO?

I have a SD Stump Puller cam with ported 62 heads and about 450hp in the 468 in my 69 GTO. Currently, I run AP Xlerator 2.5" mufflers with 14" case. I want to quiet the car a bit. These mufflers have an offset inlet and center outlet. I could go to the 18" case Xlerators. Would that be worth the swap or is there a quieter muffler with center outlet?
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Old 07-10-2019, 08:16 AM
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leeklm leeklm is offline
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I ran a very similar motor with the Dynomax Super Turbo in a 14" case. Very mellow tone. If the longer case version fits it should be even quieter.

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68 Firebird-- Street/Strip - 400/461 Eagle Forged Bottom End & Ross Flat top pistons. KRE 305 CFM and Old Faithful 2.0 from SD Performance. Crower Solid roller lifters and stainless rockers. TH400 w/low gear set. Ford 9" w/3.50 gears. Not much track time yet- but best times to date: 1.55 60ft, 6.84 @ 104mph. Hanging around 10.7's @ 125mph.
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Old 07-10-2019, 11:24 AM
RAIV55 RAIV55 is offline
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Same here, ditched the flowmasters and went with Dynomax turbos. Don't sound quite as good from outside but infinitely better from inside the car. Lost all the resonance it had before.
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Old 07-10-2019, 12:56 PM
Murphman Murphman is offline
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After 3 years the work has been completed (paint, interior, engine) with the exception of the exhaust system on my 69 GTO convertible which has been in family since ne with all matching numbers. It has the standard 350 hp with turbohydramatic with hideaways and power rear deck antenna. I am looking at exhaust systems and was leaning toward the flowmaster (17119). I have the chrome exhaust tips (2/14 inch) and would like to match the original look. You have convinced me to look at the Dynomax Super Turbo. Is that part number ST 17749? I want to have a good deep sound, but I don't want it to overpower everything. Any comments about whether I should have an X or an H pipe? Many thanks.

Murphman
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Old 07-10-2019, 05:08 PM
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I have the 17749 Super Turbos on my '64 GTO convertible - they are a 2.5" inlet/outlet muffler. I have an X pipe and the exhaust is 2.5" all the way including the 2.5" RARE RA exhaust manifolds.

Selected these mufflers so that I didn't drive myself crazy with the top down (which it is 95% of the time).

I'm very happy with the results.
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Old 07-10-2019, 06:28 PM
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Recently switched out 14" Race Pros for 21" Dynomax STs. The car is so much more enjoyable to cruise in now, especially on drives longer than 10-15 minutes.
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Old 07-10-2019, 11:29 PM
tom s tom s is offline
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I would not ever consider super turbos quiet at all.Tom
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Old 07-11-2019, 09:12 AM
71 T/A 71 T/A is offline
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I had Dynomax Super Turbos on a 72 Formula and they droned big time at 2000-2200 rpms. Installed Goerlich Xlerators and drone is gone. No way would I used those mufflers again. Terrible drone.
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Old 07-11-2019, 09:34 AM
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"You have convinced me to look at the Dynomax Super Turbo. Is that part number ST 17749? I want to have a good deep sound, but I don't want it to overpower everything. Any comments about whether I should have an X or an H pipe? Many thanks"

From what you have said, I am sure you will like the super Turbo, especially the longer case version. I have run the ST on 3 different engine combos, and was never disappointed.

Regarding X or H... I have used both on my current engine, but it is not an entirely an apple's to apples comparison. With the X I was running the long case ultraflow, and with the H am running the short case ultraflow. As expected the short case is louder, but the H tends to create more of a deeper rumble as compared to more of a "whine" with the X. Think NASCAR'ish sound with the X. In hindsight, I would have used the X in my new combo due to the louder short case ultra flows.

Many here have way more experience in this area than I do, but that was just my experience from a limited field of test cases!

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68 Firebird-- Street/Strip - 400/461 Eagle Forged Bottom End & Ross Flat top pistons. KRE 305 CFM and Old Faithful 2.0 from SD Performance. Crower Solid roller lifters and stainless rockers. TH400 w/low gear set. Ford 9" w/3.50 gears. Not much track time yet- but best times to date: 1.55 60ft, 6.84 @ 104mph. Hanging around 10.7's @ 125mph.
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Old 07-11-2019, 10:00 AM
Murphman Murphman is offline
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Great information. Many thanks. I will look into the Dynomax Super Turbos 17749 with a possible X pipe and the 1969 chrome exhaust tips which I have. Does anyone know exactly the location for the exhaust tips in relation to the bumper jack insert? How far should the tips protrude from the bumper? From the pictures I have seen it is difficult to tell especially when the exhaust systems differ. I want to keep the original look as closely as possible.

Regards,

Murphman
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Old 07-12-2019, 09:03 PM
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Here's a pic of the tips from 1969 Accessories brochure-
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Old 07-13-2019, 08:06 AM
Murphman Murphman is offline
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Thanks for the pic. New exhaust sytem will be installed next week.

Murphman
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