Quieter upgrade?

[someotherguy]

Different kinda noise though. Headers let more of a tick tick through than an actual rumble that a muffler can quell.

Noise regardless, and I hate 'em. I'm fine with a loud muffler, but I hate the sound headers make. Then the tick gets louder when they start leaking..

Richard

 

[L31MaxExpress]

My LS7 lifters are louder than my headers are. I can hear the stupid lifters at 75 mph.

The headers on my van made it quieter than it ran with manifolds.

 

[L31MaxExpress]

Both of my stock manifolds were cracked almost in half when I removed them.

This was with manifolds, could of been cracked already. This was with the junk 4L60E in it too.

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This was after the Tri-ys went on. Big gains in torque with the Thorley tri-ys.

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[NMNorsse]

What I'm telling you, is that headers are louder because they are extremely less good at attenuating noise due to the differences in material composition.

So, if modern car quiet is a priority for you, anything tubular might be a step in the wrong direction. Holley makes some higher flowing cast iron manifolds that might be an optimal compromise in this case. I would also consider thick wall exhaust tubing, I feel like my 14ga stuff helped quiet things down.

Thank you for clarifying that. I'll check out those Holley cast manifolds and see if there is thicker walled tubing out there. Today I was thinking about looking for a lower mileage late model suburban/silverado muffler and resonator at the treasure yards or something similar. Or maybe on offerup or facebook someone is listing the oem muffler etc they took out to put in a louder catback.

New OEM stuff gets the job done but is very spendy.

 

[L31MaxExpress]

Thank you for clarifying that. I'll check out those Holley cast manifolds and see if there is thicker walled tubing out there. Today I was thinking about looking for a lower mileage late model suburban/silverado muffler and resonator at the treasure yards or something similar. Or maybe on offerup or facebook someone is listing the oem muffler etc they took out to put in a louder catback.

New OEM stuff gets the job done but is very spendy.

My van has a walker quiet flow muffler on it. Quiet considering what it is muffling.

 

[Schurkey]

You have ONE factory-installed catalytic converter on that truck now.

You can install ONE new catalyst, in the same location as the "born-with" catalyst. Not two, unless you can find parts having CARB or EPA exemption. That was a legal upgrade for certain older Camaros--GM sold the pieces to do it and provided the exemption number. I'm not aware of anything like that for the GMT400 vehicles.

 

[Erik the Awful]

If I were trying to make a mostly-stock 60k mile truck run Tesla-quiet, I'd go with a set of performance-oriented cast iron manifolds. As far as I can tell, the manifolds all have a 2.5" outlet, so make sure your exhaust pipes are at least that big from there on out.

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Run dual 2.5" pipes into a Y with a 3" outlet. This will either be a DIY exercise, or a task for your muffler shop.

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Throw a 3" free-flowing cat on it.

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Put a Walker bus muffler between the cat and the rear axle.

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If you really want it quiet, put a second bus muffler after the rear axle.

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Run the exhaust out to your rear bumper and angle it downward a little.

 

[95burban]

Go to your local exhaust shop and have them build a 3in single exhaust with a large factory muffler from the scrap pile, guarantee they have tons of large factory mufflers from newer trucks.

 

[Komet]

I agree with Erik's design, it's a reasonable combo that should provide a very adequate amount of flow for a mild engine while prioritizing quiet. After the second muffler it would likely rival any modern stock vehicle.

 

[NMNorsse]

You have ONE factory-installed catalytic converter on that truck now.

You can install ONE new catalyst, in the same location as the "born-with" catalyst. Not two, unless you can find parts having CARB or EPA exemption. That was a legal upgrade for certain older Camaros--GM sold the pieces to do it and provided the exemption number. I'm not aware of anything like that for the GMT400 vehicles.

I have no doubt that is how it works in some US states. Not where I live though. At 35 years old, the truck becam exempt from emissions requirements in 2023. I can remove the cat. Since there isn't a downstream O2 sensor it won't impact the ECU.

I do want to take it with me if I move somewhere someday. So thank you for pointing out that in CARB states you've got to follow the original design.

I have to say it's insane to think I couldn't put double the cats in it.

Toyotas with a 5.7 come with 2 tubes from the header to a "2 in 1 out" muffler. Each tube has 2 cats for a total of 4.