[Lee]

Here is a dyno test I did on a mild, low compression (less than 8.0:1) 455 with stock heads, with headers.

First test had 2.5" pipes from the headers to a set of 3" FlowMasters, then to 2.25" tailpipes.

Second test is full 3" pipe, 3" 14" case Borlas ProXS mufflers, to mandrel bent 3" tailpipes. There is a 2.5" H-pipe ahead of the mufflers. First pull this combo made more power across the tested range, but the AFR leaned out big time. The test shown is after going several steps smaller on the primary metering rods (Qjet).

[besserspat]

Originally Posted by Lee

Here is a dyno test I did on a mild, low compression (less than 8.0:1) 455 with stock heads, with headers.

First test had 2.5" pipes from the headers to a set of 3" FlowMasters, then to 2.25" tailpipes.

Second test is full 3" pipe, 3" 14" case Borlas ProXS mufflers, to mandrel bent 3" tailpipes. There is a 2.5" H-pipe ahead of the mufflers. First pull this combo made more power across the tested range, but the AFR leaned out big time. The test shown is after going several steps smaller on the primary metering rods (Qjet).

It would have been interesting to see the 3" system with 2.5 tailpipes. I initially wanted the full 3" on my own 73( 461 9.5CR 232 238 HR 260 SD CNC heads and 1 3/4" dougs but my other 2 cars with 3" are loud AF.

I was hoping to run 2.5 muffs and tailpipes after a 3" pypes X pipe.. just for sake of keeping the noise down and easier fitting tailpipes than the 3" .

I spray another 200 so the 3" tails may prove beneficial.

How do.you like the Borla XS and the 3" system .? How loud , drone? Etc..
The XS were my choice for 3" dur to their slim case design that gives good ground clearance for a 3" muffler.

Thanks
Peter

[Skippy597]

My plan is to use the 2.5" flowmaster kit I got with some free flowing turbos or cherry bomb salute and then also have 3" cutouts before niecking down the the 2.5 kit so I can uncork it for the strip while being reasonable on the street. Kinda the beat of both worlds

[Lee]

"How do.you like the Borla XS and the 3" system .? How loud , drone? Etc..
The XS were my choice for 3" dur to their slim case design that gives good ground clearance for a 3" muffler."

They are ok, not very loud. They drone at around 45-55mph in my car. Here is how they sound from the outside: https://youtu.be/H0UPbZH9wfY?si=dBuUTmfkvbjYXjFB

I have large case DynoMax Welded UltraFlows (3") on another car (making ~100rwhp more) and LOVE them. I had the large case 3" RacePros on the car, and HATED them with a passion - super-raspy at full throttle, just obnoxious to my ears - but surprisingly quiet at idle.

Photo of my exhaust system attached

"with some free flowing turbos or cherry bomb salute and then also have 3" cutouts before niecking down the the 2.5 kit so I can uncork it for the strip while being reasonable on the street. Kinda the beat of both worlds"

or the worst of both worlds. If you tune the car to run best with the mufflers, then it will be really lean and run like crap when you open the cutouts. If you tune it for open exhaust, then it will be pig-rich when you close the cutouts. IMHO, the "best of both worlds" is using a quality muffler (welded UltraFlow, AP Xlerator, MagnaFlow, etc.) with a straight through design - it will make virtually the same power as open exhaust, and you only have one tune to worry about.

[besserspat]

Originally Posted by Lee

"How do.you like the Borla XS and the 3" system .? How loud , drone? Etc..
The XS were my choice for 3" dur to their slim case design that gives good ground clearance for a 3" muffler."

They are ok, not very loud. They drone at around 45-55mph in my car. Here is how they sound from the outside: https://youtu.be/H0UPbZH9wfY?si=dBuUTmfkvbjYXjFB

I have large case DynoMax Welded UltraFlows (3") on another car (making ~100rwhp more) and LOVE them. I had the large case 3" RacePros on the car, and HATED them with a passion - super-raspy at full throttle,

Its really weird the sound of the 3" XS Borlas on your car, I have put em on BBC and high strung SBC, they sounded completely different. Do you have a h pipe or x pipe? Probably the cam make it sounds quite different too

When you say large case Ultra flows , we ve used em profusely on older builds when they first came out. MY experience with magnaflow is they dont age well , I mean they sound mellow and fantastic when you put em on. But the glassmat packing inside gets packed rather quick.

Large case like more than 14 inches? Thats the main issue on Second gens , very hard to fit more than 14" muffs under the cars. Some guys were able to fit 17" muffler bodies under a second gen...

I ran a bunch of transverse systems in the past with limited success ( customers not liking the sound compared to " true duals") but sure liked the ground clearance though.

Thrush /dynomax has a super cheap transverse system that sounds a little tinny for me but decent material for like 300$ complete. Its a great system for 1st gens .

What a dilemma , its not so much about the sound quality but quietness, no drone and not leaving too much on the table either.


Peter

[Lee]

Peter,

"Do you have a h pipe or x pipe?" it has a 2.5" H-pipe.

"Large case like more than 14 inches?" Yes, 20", on a '72 A-body, plenty of room. https://www.summitracing.com/parts/WLK-17547 Replaced MVR36 RacePros (no longer available, I believe, 18" case, 3").

"What a dilemma , its not so much about the sound quality but quietness, no drone and not leaving too much on the table either." Yes sir!! I've pestered Tom Hand with muffler questions for over 2 decades now! On my '67 Firebird I did an experiment with Tom - he sent me a pair of the 3" Xlerators (still Georlich back then), 18" long cases I believe they were. I actually cut notches into them, welding-closed the "wounds", to make the mufflers fit my floorboard a bit better. My muffler guy was able to get them to fit my '67 Firebird.

It HAD 3" FlowMasters on it. The reduction in noise was astonishing! E.T. dropped nearly a tenth, and trap speed was up over 1mph. It also had a Dr. Gas X, but that was used with both mufflers.

[Formulajones]

As Lee already posted, I too also found the go to muffler to be the Dynomax Ultraflow welded cases for me. Relatively mild sound that idles and cruises nice, no drone, they do get a little louder at WOT as you would expect but that's typical. They are a straight through design and from what I've seen on dyno's and my own track testing they really don't give up much of anything, and I have electric cutouts on just about every car here.

I have a pair on my 786hp Chevelle with a complete 3" system and Dr. Gas X and 3" torque tech tails. It's very mild at cruise, easy conversations with passengers. Same exact system I ran on the previous engine that made 608hp and the level of noise difference between the 2 engines has hardly changed if at all, and they both use the same headers.

I run Dynomax on 2 other cars as well and have been happy with those. Some other cars have different setups and different systems, some transverse, some pypes etc....

[Skippy597]

Either one of you have a sound clip? How do yo think the long case cherry bomb salutes would compare? Theire stainless straight through and half the cost

[Formulajones]

I'll have to shoot a video and post on my channel for a current sound clip. There are a bunch of older sound clips that are still current on most of the cars with descriptions on my channel I can link to when a get a computer.

I haven't known anyone that has run cherry bombs in decades since mufflers now have become more refined with better high flowing design and sound control. Used to run those things in the 60's and 70's and they are very cackly and obnoxious but we've also gotten older since then.

[Skippy597]

Hey Jones, I was able to find your channel through the link in your description.

The cherry bomb salutes aren't a regular glasspack they are essentially a magnaflow knockoff with an oval case and a straight through perforated tube and steel wool and fiberglass packing. They're also under 40 bucks each.

[Formulajones]

I'll look those up, ya have me curious now. When you said cherry bombs that's an old name from 50 years ago so I immediately thought of, well, you know, the old cherry bombs lol. Which are still made by the way.

[Skippy597]

Originally Posted by Formulajones

I'll look those up, ya have me curious now. When you said cherry bombs that's an old name from 50 years ago so I immediately thought of, well, you know, the old cherry bombs lol. Which are still made by the way.

Oh ya, I've ran those on my old skylark and my k5 and while cool and sound good they are loud. I may be getting old but I like to hear myself think while driving.