Help quiet down this LT4 please
 

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.

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.

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

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/202...b7e585223d.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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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.

Resonators as mentioned above.

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

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.

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.

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.