Flapper Removal Questions on 2019 Silverado 6.2L V8

kodiakdenali · January 1, 2021

On 8/22/2020 at 8:31 PM, TNTSilverado said:

If you guys don’t want drone you gotta step up and get a full cat back. Borla, Corsa are 2 that have none.

I just installed the ATAK catback on my 6.2L I'm very happy with it. The sound at cold start up is louder than I'd like, but that may be largely due to the fact that I have to back into my garage and most of my cold starts are there, with the walls reflecting the sound back at me. once its warmed up, which takes only a minute or two, the sound smooths out and its very nice. you can hear it at all speeds, so far I've detected no drone at all and I've had a car which did drone, so badly I had to change exhausts, so I've been there. Everyone's tastes are different, for me if the exhaust forward of the catback stays stock the ATAK is a nice fit for what I want, its loud, but its not crazy loud. And Apparently you can easily and cheaply transform the ATAK into an S-Type by buying one part that replaces one of the pieces in the system with an additional muffler, just in case the ATAK is too much for your liking.

I did the install on ramps/stands. The hardest part was removing the stock tips, but even that wasn't too bad.

It costs a bit, but buy it right the first time so you don't have to buy it twice!

BluegrassMotorsport · January 2, 2021

I left both flappers in when I did the muffler delete on my 6.2. It helps keep down the drone a lot. I still get some drone on slight inclines but overall it's great. The downside is you don't get the added throttle response or increased air flow from a full catback system. For those reasons, I'm stepping up to the Corsa system soon (thanks, stimulus). Some 6.2 guys delete the rear flapper but leave the front one. That will make a little more drone but also increase air flow. There's also ways to play with the resonators in the rear to make the sound different but I haven't looked too much into that.

Edited January 2, 2021 by BluegrassMotorsport

HistoryTeacher2020 · January 4, 2021

I had a Magnaflow muffler installed. The flapper was also removed. The shop cut out the OEM muffler and installed the new one. BTW- I tried a Flowmaster 40 series but it was way too loud.

204Denali · January 5, 2021

From what I have read and researched, the down stream flapper is the one you want to keep if your only keeping 1 and looking to reduce drone. Keeping both will reduce drone more but then your restricting air flow significantly so really what is the point of the muffler swap then.

Loud factor for Borla Touring/XS (same as GM perf) < S-Type < ATAK, some find the ATAK far too loud just fyi

I have the ATAK in a custom setup. I removed both flappers in my setup, but left the screens in. I'm hearing mixed opinions that taping the screens will help with drone but then others say it does not. So no idea.

If your not going to shell out the money for a full CB, you are going to deal with drone to some degree with the Borla mufflers, its just what happens with crate mufflers. I personally do not see the CB being worth the price (and no its not that I wouldn't pay the money, I have a full Corsa/ARP setup on my vette) but it really is the only way to remove drone completely.

JohnH4260 · January 12, 2021

On 12/31/2020 at 10:20 AM, flyingfool said:

i left my flapper in, just locked it in the open position with 2 fender washers and a 2.5" long 1/4-20 screw. i found a thread on here that shows you how to do it years ago. i believe it was also a tsb update by GM tech to reduce truck fires caused by the flappers stuck closed

Do you have a link to the thread that shows how to lock the valve open? Thanks.

flyingfool · January 12, 2021

nope, search bar....

flyingfool · January 13, 2021

its simple, find the closed position, and rotate the flapper bracket open on the exhaust til it stops, now you should be able to slide your 1/4-20 x 2-3" long bolt thru the two square brackets, this is where you need the large fender washers to hold both sides together. tighten it up, and bamm you got more horsepower for $.75 of hardware

Edited January 13, 2021 by flyingfool

JohnH4260 · January 13, 2021

10 hours ago, flyingfool said:

its simple, find the closed position, and rotate the flapper bracket on the exhaust til it stops, now you should be able to slide your 1/4-20 x 2-3" long bolt thru the two brackets, this is where you need the large fender washers to hold both sides together. tighten it up, and bamm you got more horsepower for $.75 of hardware

Thank you for the information, I’ll give it a try when my truck arrives in March 2021.

JohnH4260 · January 14, 2021

Found this today on how to temporarily lock open the flapper. Photos included.
https://static.nhtsa.gov/odi/tsbs/2014/MC-10137883-9999.pdf

flyingfool · January 14, 2021

thats it!!!

RStrain56 · January 14, 2021

With my 6.2 I am wanting to do a muffler swap but may remove the 2 resonators and leave flappers in. I haven't seen any post on just a resonator removal. I would like to hear a sound clip of stock with no resonators.

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I was curious if you had done this as well? I did a muffler swap and removed the flappers, but I'm debating putting them back in. The drone isn't unbearable, just not ideal. I was also considering removing the resonators like you mentioned here as well when doing this.

Figured it was worth a shot to see!

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Denali_Joe · February 11, 2021

Get your hands on that Borla muffler if its in your budget, my truck already had the "performance package" installed when I bought it. There is NO drone and no flappers. The flowmaster in my last truck had drone, it was also louder with a glorified glass pack going straight through a "muffler"

RStrain56 · February 11, 2021

I think I'm just going to go back to the stock muffler. I enjoy a good exhaust note, but I def didn't mind it being quiet either. I've got my performance car that's modified a bit to enjoy that when needed, haha. I personally would rather spend more money tinkering with the car at this point than the truck.

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Descartian · February 14, 2021

Maybe this is too simple of an answer but it sounds like from the OP’s comments that the drone is caused by the truck going into a DFM mode. Why don’t you just turn DFM off and remove both flappers?

204Denali · February 23, 2021

On 2/14/2021 at 10:13 AM, Descartian said:

Maybe this is too simple of an answer but it sounds like from the OP’s comments that the drone is caused by the truck going into a DFM mode. Why don’t you just turn DFM off and remove both flappers?

Removing both flappers will not help with reducing drone