Help quiet down this LT4 please

[69hugger]

I recently bought a '71 Blazer with an LT4. It is a stock crate engine with stainless headers into a 3" dual exhaust with X pipe. Has Magnaflows on it and tailpipes all the way straight out the back. Sounds great at idle, but is so loud under even medium throttle, something needs to done about it.
I am not up to date on what the go-to mufflers are for those of us who want a reasonable sound level inside and for the neighbors when I leave home.
Seems to me I read something somewhere that Hooker Blackhearts might be what I'm looking for. While I want some rumble, pretty much the quieter the better.
Thanks for any help on this.

[WSSix]

What length are the Magnaflows? They might make a longer version of the same muffler. Also, add catalytic converters if you don't have them already.

[camcojb]

Yes, the longer ones are quieter. Seen good luck with resonators inline in the pipes.

[69hugger]

They look like they are the 5x8x18 size. Can’t measure them right now but based in the 3” pipe size, they look like that size to me. https://uploads.tapatalk-cdn.com/20240407/43cf8582c8779ccb28e28ab7e585223d.jpg
Can’t go much if any thicker as the truck lays frame. Could add cats or resonators if they would provide significant sound reduction.


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[srode1]

No personal experienc, but testing and other people's reports I have seen says Borla Pro XS will be your best bet for quiet and power. I have seen a couple posts from people on other sites about blackheart being too loud for their tastes.

[dhutton]

Resonators as mentioned above.

[Ns RS]

I recently bought a '71 Blazer with an LT4. It is a stock crate engine with stainless headers into a 3" dual exhaust with X pipe. Has Magnaflows on it and tailpipes all the way straight out the back. Sounds great at idle, but is so loud under even medium throttle, something needs to done about it.
I am not up to date on what the go-to mufflers are for those of us who want a reasonable sound level inside and for the neighbors when I leave home.
Seems to me I read something somewhere that Hooker Blackhearts might be what I'm looking for. While I want some rumble, pretty much the quieter the better.
Thanks for any help on this.

Running stock lt4 with black heart exhaust 3” x pipe etc and I had the opposite problem as you - the black heart system is great but was too quiet with resonators so I cut them out and they work great - so yes resonators

[Hotwire]

Unfortunately it's the 3" exhaust that's getting you. I've run into the same issue with my car.

I ended up putting 3" high flow magnaflow cats on the collectors of my longtubes and it greatly reduced the sound level in the car, can carry on conversations easily while cruising now. I am also running an Elgin E1839P cam, has a lot of overlap, and the exhaust stank at idle, the cats cleaned it up, don't smell like I mowed the lawn after driving around now.

[bk2life]

Unfortunately it's the 3" exhaust that's getting you. .

This right here.

amazing going from 3 inch to 2.5 inch would be.

Cats help alot, as theyre 'mini' mufflers, and you can always add a second muffler.

Some people like resonators, but, those are straight through 'glass packs' and they will tone it down, but, theyre still plenty loud.

Your exhuast system looks nice, but, it needs to be redesigned for what you want.

[rstone]

Another thing to consider is a blazer is not the same as a car or a pickup, as the passenger compartment extends all the way to the back bumper. Cars and Pickups have a separation from the exhaust tips. Insulation in the floor of the bed is essential to deadening the sound. I had a 76 blazer with no sound deadening. It sat 4" off the ground and had cam with a lot of overlap and the old flowmaster 5 chambers on it dumpt to the ground in front of the rear end. You could carry on conversation in it. all though it did set off every car alarm I passed.

[69hugger]

All great points.
As I just bought the vehicle and have hardly driven it yet, I am going to give it some miles before I commit to a major redo of the system. A couple different mufflers I could see doing. But a more major change will probably have to wait.
Thanks for your input.

[WSSix]

I completely forgot about asking where and how the exhaust exits. That's a great point. Does it go past the axles and exit past the body or under the body?

[srode1]

All great points.
As I just bought the vehicle and have hardly driven it yet, I am going to give it some miles before I commit to a major redo of the system. A couple different mufflers I could see doing. But a more major change will probably have to wait.
Thanks for your input.Borla Pro XS swap would be your easy to try swap, and would give me a nice preview of how they will sound on mine if you do it! :)

[69hugger]

I completely forgot about asking where and how the exhaust exits. That's a great point. Does it go past the axles and exit past the body or under the body?
The exhaust goes full length out the back, under the bumper.

[67_camaroRS]

wow here i am, thinking magnaflow mufflers were too quiet. Borla ATTK hit the spot. :lol:

[PTAddict]

I had a complete 2.5" magnaflow exhaust system on my 67 Chevelle 'vert with a stock LQ9 (hi-po truck LS). It was too loud and droned obnoxiously between 1500 and 2500 RPM. I replaced the Magnaflow mufflers with DynoMax Super Turbos - much quieter and the drone is almost gone. Hard to exaggerate the difference.

[71OLDS]

another vote for DynoMax Mufflers. I have them on my 468 Olds motor in my 71 442 with 3" pipes and they are fairly quiet until you go WOT. Here's the details including the part #s on the mufflers:

Hooker SuperComp Jet Hot coated 1 7/8" tubes, 3 1/2" collectors, into a 3 1/2” down to 3” reducer, into a 3” X crossover, into 3” in Dynomax Ultra Flow welded Mufflers(17229), into 3” tail pipes, into 3” Olds trumpets

[PTAddict]

another vote for DynoMax Mufflers. I have them on my 468 Olds motor in my 71 442 with 3" pipes and they are fairly quiet until you go WOT. Here's the details including the part #s on the mufflers:

Hooker SuperComp Jet Hot coated 1 7/8" tubes, 3 1/2" collectors, into a 3 1/2” down to 3” reducer, into a 3” X crossover, into 3” in Dynomax Ultra Flow welded Mufflers(17229), into 3” tail pipes, into 3” Olds trumpets

Just to note, the Dynomax Super Turbo is a quite different design than the Ultra Flow. The Ultra Flow is a "straight through" design, and will likely be a fair bit louder than the Super Turbo.

[X.K5]

Blazers were known to have exhaust fume problems running them strait out the back, gets sucked under the tailgate and hatch, if you have it on. Maybe somebody else knows if a turn down on the end would help..