Longtubes/catless y pipe sewing machine

scottie350 · January 14, 2019

Hey guys, so this is on a 16 Sierra 5.3. After going to LTs and catless y pipe i seem to have whats best described as a loud sewing machine sound. I know stock manifolds are thicker which equals more valvetrain noise but is everyone just dealing with this obnoxious noise?

I cheaped out a bit and went with pace-setters but i did have cause. Ive seen several dynos of huge gains on pacesetters on these trucks and reviews from guys saying theyve lasted them several years and still going, which by then id be into a new truck anyway.

Ive checked for a leak leak, loose plugs, caps, nothing i can find.

Thinking pacesetter headers and y pipe gauge size likely thinner ive been searching. Oddly enough PS are the same or thicker gauge than most recommended brands. Which is where im now stumped with this sound.

It doesnt come from the headers, it primarily seems to reverb through the y pipe area. Can hear it at cold start, or at higher gear low rpm cruising from beneath the front seats, like a loud ass sewing machine. Ive seen posts on the vette forums that this tends to be a tad normal over there with catless LTs, not much on these trucks tho.

So what, is this common and u guys deal or? PS uses 16 gauge on the lts and 16 gauge on the y pipe, kooks are 18 gauge LT and 16 gauge y pipe. Honestly super annoyed with the sound, ready to put the stocks back on thats how annoying it is to me.

300 Blackout · January 20, 2019

I have speed engineering long tubes, no cats, dual 3” exhaust with an x pipe. The metal is 304 stainless and 16 gauge. I do not have any such noise.

The engine itself, I can hear the valve-train doing its thing. Honestly, not really bothersome to me. The exhaust produces no such sound. Just a deep rumble.

I tuned out V4 mode so my truck is always in V8.

scottie350 · January 20, 2019

13 hours ago, 300 Blackout said:

I have speed engineering long tubes, no cats, dual 3” exhaust with an x pipe. The metal is 304 stainless and 16 gauge. I do not have any such noise.

The engine itself, I can hear the valve-train doing its thing. Honestly, not really bothersome to me. The exhaust produces no such sound. Just a deep rumble.

I tuned out V4 mode so my truck is always in V8.

Thanks for the reply. Mines custom tuned with v4 shut off. Sound doesnt come from engine, dominantly radiates from the y pipe.

Something ive been considering is where it ys into single pipe causing the increased noise. Because it seems to be radiating from the y pipe this seems logical.

Ive been wondering myself if going to duals with an x pipe would drop this off. By your setup i could be on the right track.

Im going to take the truck to the custom exhaust shop and have him take a look and then see what he thinks.

Barman84 · January 27, 2019

On 1/19/2019 at 10:18 PM, 300 Blackout said:

I have speed engineering long tubes, no cats, dual 3” exhaust with an x pipe. The metal is 304 stainless and 16 gauge. I do not have any such noise.

The engine itself, I can hear the valve-train doing its thing. Honestly, not really bothersome to me. The exhaust produces no such sound. Just a deep rumble.

I tuned out V4 mode so my truck is always in V8.

What did you do about your rear 02s???

DirtyMarcus · January 27, 2019

Most LS and LS based engines make the "sewing machine" sounds. Its usually the rocker arms making the noise. Not an issue just noise. However, if you want to fix it due the trunion upgrade. https://www.texas-speed.com/p-5982-che-lslt-trunion-kit-for-stock-rockers-bushings.aspx

300 Blackout · January 27, 2019

What did you do about your rear 02s???

I disconnected them and am running with a check engine light for now. I put money down on a supercharger and the tune that comes with it can be modified to shut off the rear O2s. Unfortunately, the truck was just rear-ended last week and I’m in a rental until I find out if they are gonna replace my frame.

scottie350 · January 29, 2019

On 2019-01-27 at 11:15 AM, Barman84 said:

What did you do about your rear 02s???

Clipped mine to keep the plug in so it doesnt ruin the plugs in the harness, then tuned them out. If ever need to i can splice the o2s back on.

scottie350 · January 29, 2019

On 2019-01-27 at 1:04 PM, DirtyMarcus said:

Most LS and LS based engines make the "sewing machine" sounds. Its usually the rocker arms making the noise. Not an issue just noise. However, if you want to fix it due the trunion upgrade. https://www.texas-speed.com/p-5982-che-lslt-trunion-kit-for-stock-rockers-bushings.aspx

Yeah this has been my consensus recently. Most info i find on the vette forums but guys have mentioned this noise from ls engines. One guy posted a vid and its exactly what mine sounds like. Normal at idle and even in park revving, notice it at higher gear/low rpm under load. Havent found a confirmation if a true dual with x pipe will lessen it, 300blackout says doesnt have this noise w his setup. Ill check out the kit you posted. Thanks for the confirmation Marcus, at the very least, perhaps i just need a louder exhaust baha

crushNchowda · January 29, 2019

google "sewing machine noise" on an GM LSx/LTx forum & you'll find more threads citing similar whether it be injectors, rockers, valves or intake noise or a combo of it all -but its not uncommon.....you did get the cheapest headers money can buy, your $$$ your choice - correct they'll def boost HP, but they're constructed of aluminized mild steel, not sure on the gauge but probably is thicker than most competitors made outta stainless b/c there's going to be oxidization/pitting occuring w/ the PS's & they need to hold up, I would've had them ceramic coated if it were me....

At any rate I also notice these trucks have more sound emitting from the lower driver's footwell area, I believe someone @ some point tracked it down to lack of heat shield/sound deadening material in a certain area near the steering column? Anyhow - ever since I added my Gibson exhaust I've had more sound coming in cabin engine & exhaust, I thought was exhaust leak initially but crawling underneath don't see any evidence of such & after coming across the thread I mention above chalked it up to that. The dealer couldn't locate any leaks either (not that that means much)

I don't have headers, but I can imagine the sound from the engine bay would be MUCH louder since I can hear it now @ some throttle/rpm levels, headers magnify drivetrain/engine sounds for sure.

Edited January 29, 2019 by crushNchowda

DirtyMarcus · January 29, 2019

5 hours ago, scottie350 said:

Yeah this has been my consensus recently. Most info i find on the vette forums but guys have mentioned this noise from ls engines. One guy posted a vid and its exactly what mine sounds like. Normal at idle and even in park revving, notice it at higher gear/low rpm under load. Havent found a confirmation if a true dual with x pipe will lessen it, 300blackout says doesnt have this noise w his setup. Ill check out the kit you posted. Thanks for the confirmation Marcus, at the very least, perhaps i just need a louder exhaust baha

I will say this, on my ls1 swapped mustang i have cutouts so basically straight from the headers exhaust. I can hear the rocker noise over the exhaust outside the car and with the hood popped its extremely noticeable. Inside the car I cant hear it though. I plan to do the trunion upgrade eventually but its not something that bothers me too much.

scottie350 · January 29, 2019

2 minutes ago, DirtyMarcus said:

I will say this, on my ls1 swapped mustang i have cutouts so basically straight from the headers exhaust. I can hear the rocker noise over the exhaust outside the car and with the hood popped its extremely noticeable. Inside the car I cant hear it though. I plan to do the trunion upgrade eventually but its not something that bothers me too much.

Welll crap, it drives me nuts, i may have to do the upgrade. Im super ocd about some things.

scottie350 · January 30, 2019

12 hours ago, crushNchowda said:

google "sewing machine noise" on an GM LSx/LTx forum & you'll find more threads citing similar whether it be injectors, rockers, valves or intake noise or a combo of it all -but its not uncommon.....you did get the cheapest headers money can buy, your $$$ your choice - correct they'll def boost HP, but they're constructed of aluminized mild steel, not sure on the gauge but probably is thicker than most competitors made outta stainless b/c there's going to be oxidization/pitting occuring w/ the PS's & they need to hold up, I would've had them ceramic coated if it were me....

At any rate I also notice these trucks have more sound emitting from the lower driver's footwell area, I believe someone @ some point tracked it down to lack of heat shield/sound deadening material in a certain area near the steering column? Anyhow - ever since I added my Gibson exhaust I've had more sound coming in cabin engine & exhaust, I thought was exhaust leak initially but crawling underneath don't see any evidence of such & after coming across the thread I mention above chalked it up to that. The dealer couldn't locate any leaks either (not that that means much)

I don't have headers, but I can imagine the sound from the engine bay would be MUCH louder since I can hear it now @ some throttle/rpm levels, headers magnify drivetrain/engine sounds for sure.

I normally dont keep my vehicles long. My intention was to get some more fun out of it while i had it and then swap it back to stock before i traded it. So looking at dynos done settled to save cash as i knew id get that. Im not worried about longevity, theyll last just fine aslong as im gonna have the truck. I had the headers stripped and coated myself, the extra 300 for the ceramic they send it in isnt worth it from the countless hours searching i did, it tends to chip off as ANY bump can damage the coating in transit, got em coated locally for half the price.

Given the gauge of metal used i was curious if others hear this or if i was missings something. Oddly i could only find searches leading me to the vette forums but they said the same thing over there about the ls motors and headers/catless... valvetrain noise. The video a forumer there and his explanation of the conditions confirmed thats what im hearing.

Ive modified most of my vehicles, some quite heavily, never heard this before without finding a problem, first time on an ls engine so its been bugging the hell out of me. Not finding a culprit i needed to know if it was a normal noise or if i was overlooking something. Seems its normal though, and either ill have to learn to live with it or try the rocker bushing upgrade that Marcus posted

scottie350 · January 30, 2019

On 2019-01-19 at 10:18 PM, 300 Blackout said:

I have speed engineering long tubes, no cats, dual 3” exhaust with an x pipe. The metal is 304 stainless and 16 gauge. I do not have any such noise.

The engine itself, I can hear the valve-train doing its thing. Honestly, not really bothersome to me. The exhaust produces no such sound. Just a deep rumble.

I tuned out V4 mode so my truck is always in V8.

Btw just realized ur using SE LTs, is ur exhaust thier true dual kit also?

300 Blackout · January 30, 2019

Btw just realized ur using SE LTs, is ur exhaust thier true dual kit also?

Yes, it’s their true dual exhaust and their headers. Exhaust sounded awesome but the drone was killer so I added two Borla Pro XS mufflers before the SE mufflers. Drone got worse. Now, I’m gonna delete the SE mufflers and add high flow cats just after the x-pipe. After the cats I’ll keep the Borla mufflers then a dual exit in front of the passenger side rear tire. Hopefully that will fix the drone and keep it quiet enough for the neighbors.

I do hear my valve train at idle or when pulling through a drive thru but it isn’t a sound that I hear in the exhaust.

Right now, the loaner I’m driving is a 2018 F-150 with 3,000 miles on it. It’s no different than our trucks. It has its fair share of engine noises and ticks that I could drive myself nuts with trying to find.

scottie350 · January 30, 2019

10 minutes ago, 300 Blackout said:

Yes, it’s their true dual exhaust and their headers. Exhaust sounded awesome but the drone was killer so I added two Borla Pro XS mufflers before the SE mufflers. Drone got worse. Now, I’m gonna delete the SE mufflers and add high flow cats just after the x-pipe. After the cats I’ll keep the Borla mufflers then a dual exit in front of the passenger side rear tire. Hopefully that will fix the drone and keep it quiet enough for the neighbors.

I do hear my valve train at idle or when pulling through a drive thru but it isn’t a sound that I hear in the exhaust.

Right now, the loaner I’m driving is a 2018 F-150 with 3,000 miles on it. It’s no different than our trucks. It has its fair share of engine noises and ticks that I could drive myself nuts with trying to find.

Ive been looking at that kit, how loud was it w the SE mufflers? Mostly at cold start? 530am starts wondering how POd neighbors gonna be lol.

As for the valvetrain i likely hear it so much bc im focusing so much on it when driving, but yeah def at drive throughs ill deal w that later haha