[android 211]

After a prolonged wait I finally have my 1969 GTO convertible. Power is a 455 with '96' heads and 068 HO cam. Log manifolds. I bought the Pypes 2 1/2" headpipes. There is a 2 1/4" inlet mated to the manifold which immediately flares out to 2 1/2". The 2 1/2" pipes go back to long case Dynomax mufflers. I think they're 17449s. After that I had a reducer made to connect to the Waldron's 2 1/4" tailpipes that have resonators since all automatic 1969 GTOs had resonators. Without asking me the installer welded in a H pipe. The result is super quiet. Out on the highway the exhaust is a low hum. The H pipe eliminated that GTO gargle noise as Motor Trend once called it. I'm not sure if I'll change it. I'm sure I have low restriction. Just wanted to warn people seeking more of a performance sound. I used the same mufflers with 2 1/4" inlet/outlet and no X or H or resonators on a friends '67 Lemans with a mild 400 and it sounded pretty good. I think the H pipe is what really quieted the car down.

[Gator67]

I replaced the Race Pros on my 67 convertible with long Dynomax to get rid of drone.... they are a lot quieter, especially at cruising rpms. Much more enjoyable to me.

[leeklm]

Yep, I like those mufflers for a street cruiser where you want to listen to the radio, but for a "performance sound", it is tough to beat the Dynomax ultraflows IMO.

In my 73 with big motor, had the long case ultraflows with 3"x pipe and full headers, sounded great, but maybe a little loud for driving to church. When selling the car, I installed the stockish 400 with log manifolds, but left the x pipe and mufflers installed. Was of course quieter, but still had a nice tone.

My firebird build will have same motor, but now with 3" everything, H pipe, and 14" ultraflows. I am looking forward to hearing the results. Hopefully in 2-3 weeks!

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[Lee]

Originally Posted by android 211

After a prolonged wait I finally have my 1969 GTO convertible. Power is a 455 with '96' heads and 068 HO cam. Log manifolds. I bought the Pypes 2 1/2" headpipes. There is a 2 1/4" inlet mated to the manifold which immediately flares out to 2 1/2". The 2 1/2" pipes go back to long case Dynomax mufflers. I think they're 17449s. After that I had a reducer made to connect to the Waldron's 2 1/4" tailpipes that have resonators since all automatic 1969 GTOs had resonators. Without asking me the installer welded in a H pipe. The result is super quiet. Out on the highway the exhaust is a low hum. The H pipe eliminated that GTO gargle noise as Motor Trend once called it. I'm not sure if I'll change it. I'm sure I have low restriction. Just wanted to warn people seeking more of a performance sound. I used the same mufflers with 2 1/4" inlet/outlet and no X or H or resonators on a friends '67 Lemans with a mild 400 and it sounded pretty good. I think the H pipe is what really quieted the car down.

Or maybe the resonators are the reason it is quiet.

[NeighborsComplaint]

I put an H pipe in mine and immediately noticed the loss of that nice “cammy” idle sound I had from my RA4 spec cam. It sounds like a police cruiser now.

The first thing I will be doing this spring is a trip to the muffler shop and new set of individual exhaust pipes.

[OCMDGTO]

You guys are crazy, quiet is good on a street car. Especially on a road trip for a few hours. I wouldn't change a thing, drive and enjoy!

[Formulajones]

I prefer a little bit of quiet these days. I really like the Dynomax 17449's and the Ultraflows. Both have a pretty nice mellow sound, and I always run an X-cross over on all of them.

It's most likely those resonators at the tails that really quieted things down and the fact that you reduced the tailpipes size to 2 1/4" also helps to tame things down.

Usually when I have a system that is a little on the obnoxious side I'll reduce the tailpipe size. Takes some of the deep droning sounds out and mellows things down. Did that on our Camaro and my wife went from hating the exhaust to now loving it.

[GT182]

I have the H pipe with 2.5" pipes from just in front of it back thru Cherry Bomb mufflers. 2" off the stock exhaust manifolds then into the 2.5" pipes. That will be changed later this summer I hope. My 400 has a nice little rumble because of the cam and it gets louder the more you mash the gas. When you let off from really mashing the gas it pops and crackles as it should.

The Cherry bombs are loud enough going down the highways but not so bad that you can't hear yourself think or hear the radio with the windows down. And not as obnoxious as some I've heard.

[Scarebird]

Originally Posted by Formulajones

...It's most likely those resonators at the tails that really quieted things down and the fact that you reduced the tailpipes size to 2 1/4" also helps to tame things down...

We have a 70 GTO here in ABQ that still has the original
exhaust - very quiet.

[Formulajones]

Originally Posted by Scarebird

We have a 70 GTO here in ABQ that still has the original
exhaust - very quiet.

Yep, when my father bought his 69 GTO new, first thing he did was pull off the resonators because it was too quiet. Still have those in a box.

Our 69Z still had it's born with exhaust system intact until last year when I pulled it off for a 2 1/2" Pypes setup. The original system was pretty quiet even though it had what GM called a "deep tone" muffler on it. Wife was happy with the sound level but I was looking for a performance boost. So on went the Pypes system, however I was able to get the sound to an acceptable level by installing factory 2" tails on the Pypes system and made my wife happy.