[Formulajones]

On my 454 pickup I ran 3" dual with no cross over at all and had race pros on that. It was so loud everyplace that my wife simply said I had just ruined that truck, lol. I swapped for a set of street pros and the truck became so docile sounding everyplace you wouldn't think it had a nice running 454 in it.

I restored a 69 Mach 1 mustang for a customer and did a complete 2 1/2" Pypes system on it with "X" and race pros. Was a nice roller cam 351 W build. It was loud but sounded good, I think the Fords sound better with it, but it had drone right around 2,000 rpm. Ended up switching that over to street pros and they were much happier with the car.

Anymore, I skip the race pros and go right for dynomax ultraflow mufflers. I've never had an application with those mufflers to date on any type of car that was excessively loud or had any drone to speak of. They are more expensive but I've been more impressed with the sound quality and control of those mufflers.

On the transverse systems we are limited. Pypes sells one, and it comes with a crossflow muffler with a racepro design. The other one on the market is made by Thrush with a dynomax muffler.
Something about the crossflow design however that the racepro isn't excessively loud, doesn't exhibit any drone and produces better sound quality than the dual muffler race pro setup. I run this system on 2 cars here and like it. On my wife's car she wanted it a bit more quiet. I also wanted stock appearance with factory tail pipes. So I grafted the 2" factory tail pipes into the transverse muffler. That small change completely changed the sound of the car everyplace. To the point that when cruising, inside the car, you hear the engine in front of the firewall more than the noise out the tailpipes, which makes a very comfortable car. But it will bark a bit when you stand on the throttle. I've been impressed with that change.

All kinds of stuff you can do to affect sound.

[1stgenbird]

I have a similar Pypes setup with Racepros on my 67 Firebird 400 with LB manifolds. No drone at all. Love the sound.

[78w72]

Originally Posted by Formulajones

On my 454 pickup I ran 3" dual with no cross over at all and had race pros on that. It was so loud everyplace that my wife simply said I had just ruined that truck, lol. I swapped for a set of street pros and the truck became so docile sounding everyplace you wouldn't think it had a nice running 454 in it.

I restored a 69 Mach 1 mustang for a customer and did a complete 2 1/2" Pypes system on it with "X" and race pros. Was a nice roller cam 351 W build. It was loud but sounded good, I think the Fords sound better with it, but it had drone right around 2,000 rpm. Ended up switching that over to street pros and they were much happier with the car.

Anymore, I skip the race pros and go right for dynomax ultraflow mufflers. I've never had an application with those mufflers to date on any type of car that was excessively loud or had any drone to speak of. They are more expensive but I've been more impressed with the sound quality and control of those mufflers.

On the transverse systems we are limited. Pypes sells one, and it comes with a crossflow muffler with a racepro design. The other one on the market is made by Thrush with a dynomax muffler.
Something about the crossflow design however that the racepro isn't excessively loud, doesn't exhibit any drone and produces better sound quality than the dual muffler race pro setup. I run this system on 2 cars here and like it. On my wife's car she wanted it a bit more quiet. I also wanted stock appearance with factory tail pipes. So I grafted the 2" factory tail pipes into the transverse muffler. That small change completely changed the sound of the car everyplace. To the point that when cruising, inside the car, you hear the engine in front of the firewall more than the noise out the tailpipes, which makes a very comfortable car. But it will bark a bit when you stand on the throttle. I've been impressed with that change.

All kinds of stuff you can do to affect sound.

i trust your experiences with them, just saying my experience. each person/car is different it seems, some love the racepros & say they dont have drone, some say they do. pypes themselves say the street pros are louder & most videos ive seen including the ones pypes has, seems like the street pros are louder, at least at idle & low to mid rpms. at WOT the race pros are probably louder since they are straight through open design. but again, every application is different with too many variables that determine final sound.

strange the dynomax ultra flos would be such a dramatic difference vs the race pros, they are essentially the same muffler physically, just have slightly different packing.

[Formulajones]

I think where the Dynomax gain their sound control is with that larger 20" case muffler, they are much bigger than the Racepros.

However, I say that and run the smaller 14" dynomax ultraflows on my sons 5.0 mustang and love the mellow sound they provide. No drone, and not excessively loud like most fox bodies that run around. It has more of a mellow muscle car rumble that really doesn't grab much attention. Even removed the cats on it (it had 4 of them, lol) And generally the fastbacks tend to transmit more exhaust noise due to the fact that the rear cargo area is part of the passenger compartment (they don't have a separate trunk) yet the car is very comfortable to drive.

[78w72]

i can see that, but not really apples to apples to compare a 20" case to a 14" case. i'd bet the 14" dynomax is a very similar sound to the 14" racepros.

[Formulajones]

That's just it, the 14" dynomax case you would think would be louder but it's very docile. Extremely tame on my sons car. When I run the Racepro mufflers they are definitely much louder than a 14" dynomax.

I have a ton of idle, race, and cruise clips of different exhaust setups I've tried. When I get some time I'll post some video. But not sure what that would really accomplish since everyone has a different idea of what is loud, what is drone etc...so it's impossible to hash out the differences on a computer.

[78w72]

Originally Posted by Formulajones

That's just it, the 14" dynomax case you would think would be louder but it's very docile. Extremely tame on my sons car. When I run the Racepro mufflers they are definitely much louder than a 14" dynomax.

I have a ton of idle, race, and cruise clips of different exhaust setups I've tried. When I get some time I'll post some video. But not sure what that would really accomplish since everyone has a different idea of what is loud, what is drone etc...so it's impossible to hash out the differences on a computer.

fully agree, thats what ive always said about things like this... the member that posted this thread says his race pros have terrible drone & have to go... others chime in saying their race pros dont have any drone, are not loud & sound great! some people like red cars, & some don't.

[sjdiesel]

Got the dynomax st’s Installed. All I can say is wow! I am extremely happy with the outcome. Driving it is now a pleasure with no real drone. There is some slight drone below 20 mph but totally manageable. Nothing like the drone with the RP’s. Did a couple WOT runs and I can’t tell any performance difference. The car feels so much better now that I can hear myself think while driving. Here is a quick video.
https://photos.app.goo.gl/MDN7KUc72fwDgkhA7

Thanks everyone for all the advice.

[Formulajones]

Originally Posted by sjdiesel

Got the dynomax st’s Installed. All I can say is wow! I am extremely happy with the outcome. Driving it is now a pleasure with no real drone. There is some slight drone below 20 mph but totally manageable. Nothing like the drone with the RP’s. Did a couple WOT runs and I can’t tell any performance difference. The car feels so much better now that I can hear myself think while driving. Here is a quick video.
https://photos.app.goo.gl/MDN7KUc72fwDgkhA7

Thanks everyone for all the advice.

And that's pretty much been my experience with just about every brand of car here. Glad you got it squared away. Sometimes exhaust can be a frustrating thing to find what you're looking for.

[Gator67]

Originally Posted by sjdiesel

Got the dynomax st’s Installed. All I can say is wow! I am extremely happy with the outcome. Driving it is now a pleasure with no real drone. There is some slight drone below 20 mph but totally manageable. Nothing like the drone with the RP’s. Did a couple WOT runs and I can’t tell any performance difference. The car feels so much better now that I can hear myself think while driving. Here is a quick video.
https://photos.app.goo.gl/MDN7KUc72fwDgkhA7

Thanks everyone for all the advice.

I too have RPs & x-pipe on my 67 and have the same drone as in your videos. Thanks for posting the video with the dynomax mufflers installed, sounds much better, will be ordering two! Did you get the 14” or 20”?

[Formulajones]

Originally Posted by sjdiesel

Got the dynomax st’s Installed. All I can say is wow! I am extremely happy with the outcome. Driving it is now a pleasure with no real drone. There is some slight drone below 20 mph but totally manageable. Nothing like the drone with the RP’s. Did a couple WOT runs and I can’t tell any performance difference. The car feels so much better now that I can hear myself think while driving. Here is a quick video.
https://photos.app.goo.gl/MDN7KUc72fwDgkhA7

Thanks everyone for all the advice.

Duh, I just noticed you have a video link, lol. Yes that's the mellow muscle car sound I was referring to earlier. Haven't really found any other muffler that captures that sound and I've used Racepro, Streetpro, Magnaflow, Flowmaster in at least 3 different chamber configurations, Thrush, SLP, Spintech, and quite a few cheap muffler shop setups, and probably a couple names I don't even remember anymore. I keep going back to the Dynomax and pretty much that's all I'll buy now.

[sjdiesel]

Originally Posted by Gator67

I too have RPs & x-pipe on my 67 and have the same drone as in your videos. Thanks for posting the video with the dynomax mufflers installed, sounds much better, will be ordering two! Did you get the 14” or 20”?

I probably lost at least one nights sleep trying to decide on the 14” or 20”. In the end I went with the 20” p/n 17749 and couldn’t be happier. I think the car sounds better than the RP’s and it is sooooooo much nicer to drive!!!! I just got back from running a bunch of errands with my daughter and I am very happy.

Good luck and post up a before and after video.

[Gator67]

Originally Posted by sjdiesel

I probably lost at least one nights sleep trying to decide on the 14” or 20”. In the end I went with the 20” p/n 17749 and couldn’t be happier. I think the car sounds better than the RP’s and it is sooooooo much nicer to drive!!!! I just got back from running a bunch of errands with my daughter and I am very happy.

Good luck and post up a before and after video.

Thank you for the part number. I like to drive my car, but on trips longer than 45 minutes or so, I've always found it a bit fatiguing. Really look forward to the change.

[leeklm]

This discussion is timely, as I weigh options for my 68 firebird. I ran the 20" ultra flow in my gto with 3" mid and headers, 600hp, and was very happy. Same engine going into the 68 and plan on the 3" Pypes X.

I thought the 1st gen fbody may need a 14" case, but sounds like the 20" case should work?

I was considering the complete kit from Pypes with either the Street or Race Pro- but after reading this- thinking I will stay with dynomax and the pypes mid section. I also like their Super Turbo, but sounds like it is not a true 3" muffler. Someone reported the ST input flange is 3", but internals are 2.5". Probably not a huge deal for me, but if buying 3", I want 3" !

Sent from my SM-G965U using Tapatalk

[69f bird]

I had a similar drone in my '69 Firebird convertible. I had the Pypes 2 1/2" system with an X, with 14" Dynomax Race Magnums. It was too loud, we could not hear each other talk while driving the car, and the drone was obnoxious.

I replaced the mufflers with 16" Dynomax ST's this fall. I love it. Still sounds like a muscle car, but no drone and I can have a conversation in the car! I bought 14's, 16's and 20's, hoping to install the largest that we could fit without major modifications.

[Gator67]

Originally Posted by sjdiesel

Got the dynomax st’s Installed. All I can say is wow! I am extremely happy with the outcome. Driving it is now a pleasure with no real drone. There is some slight drone below 20 mph but totally manageable. Nothing like the drone with the RP’s. Did a couple WOT runs and I can’t tell any performance difference. The car feels so much better now that I can hear myself think while driving. Here is a quick video.
https://photos.app.goo.gl/MDN7KUc72fwDgkhA7

Thanks everyone for all the advice.

I just replaced the 14" Racepros on my car with the 20" Dynomax STs hoping for the same outcome. Bingo! So much nicer at cruising rpm. Only downside is a little less snarl when doing a WOT blast...a very good deal for less than $150!

[sjdiesel]

That is great! Glad it worked out for you too.

[OCMDGTO]

Great info & sounds like 20" is the way to go. I'm going to run my VTs till they fall off but now I know what to get. Nice car and combo sj, you ever take that car to the track?

[sjdiesel]

Originally Posted by OCMDGTO

Great info & sounds like 20" is the way to go. I'm going to run my VTs till they fall off but now I know what to get. Nice car and combo sj, you ever take that car to the track?

No track time yet. I just got it running in early December and am working out the bugs.

[Formulajones]

Originally Posted by sjdiesel

No track time yet. I just got it running in early December and am working out the bugs.

Bring it out to Pontiac Heaven. Paul is usually there if he can find the free time and there are a handful of us locals that like to race our street cars. Usually a light turnout so you get all the passes in you want, great opportunity to find what the car likes and get things dialed in.

I believe the next event is scheduled for November.