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Discussion Starter · #1 ·
Hey, all. I'm having a bit of a conundrum with some knock and funky ticking/ fluttering sounds on my 6.4. Last year I got some Kook long tubes and catless mids installed, along with solid motor mounts and a nitrous kit (which I really haven't used) and installed an email tune from a reputable tuner. Shortly after, I went on a work trip for about 8 months that I came back from about a month ago. Before I left, and about a week or 2 after I got back, the car drove and sounded great with zero issues. Then I started to see some consistent STK on my Trinity. Anywhere between 2-10 degrees between 2000-3500ish RPMs. At first, I went to the fuel as it had a quarter of a tank that had been sitting for a good while before I topped it off with fresh BP93. Still got knock, so I drained the tank, filled up with Sunoco 93 and a bottle of Royal Purple octane booster with no change. The car is making a a fluttering/ ticking sound, but only under acceleration and again, at 2k and up. We found a header bolt that had backed out quite a bit, so we tightened it back down and checked torque on all the bolts, but didn't see any soot deposits or any visual signs of a leak. At the same time, we did an oil change with Amsoil and an SRT filter. The car STILL makes noise and still picks up knock while driving and in neutral, albeit a little less. Also a weird thing to note, if I Rev in neutral and let off at around 4-5k, I can hear a pretty noticeable whoosh of air, almost like a turbo blow-off, so I'm still optimistic in thinking there's an exhaust leak somewhere the sensors are picking up. The only thing we haven't tried yet, short of opening up the block, is a stetho or smoke test. I'm hoping someone here has some input that can help me in the right direction before I start tearing into things I don't need to as I know longtubes are pretty notorious about resonating engine noise you normally wouldn't hear or notice. Thanks in advance!
 

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If it were me....
1) inspect and tighten all the exhaust bolts/clamps (you already found problems)
2) Return to the stock tune. You have not done THAT much to the engine that you need a custom tune. Your knock issues can be attributed to timing issues where you don't have any.

When in doubt return to base line and build from there.
 

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2020 Dodge Challenger Hellraisin Scat Pack
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Would add to what bill....5842 offered is with the one exhaust leak the exhaust gasket (or gaskets) could be compromised and leak even with header bolts tight. And not all exhaust gaskets are equal. There have been posts on which ones are best. But I have no links to offer.

I'd look into what are the best gaskets to use and get them and install them and run the engine one full cycle to full operating temperature then let the engine cool down overnight then check the header bolts torque.
 

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Discussion Starter · #4 ·
Would add to what bill....5842 offered is with the one exhaust leak the exhaust gasket (or gaskets) could be compromised and leak even with header bolts tight. And not all exhaust gaskets are equal. There have been posts on which ones are best. But I have no links to offer.

I'd look into what are the best gaskets to use and get them and install them and run the engine one full cycle to full operating temperature then let the engine cool down overnight then check the header bolts torque.
Thanks for the input. Everyone says new OEM gaskets are best, so that's what I went with. I still have the original gaskets that came off with stock manifolds as well as a new set of Cometic that came with the Kooks. One of my buddies suggested a smoke test to see if there's any leakby as well.
 

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I have had issues with a leak where the cat pipes meet the rest of the exhaust under the driver's compartment. I had to expand the cat pipes slightly to make them fit into the rear section better and put a long breaker bar on the clamp bolts to get them tight enough. It's hard to get good leverage laying on your back under the car.

If you push up on the exhaust system and see any movement at a connection point you'll need to do some work to tighten things up.

Your knock is probably from something hitting the exhaust system though. Check all the foil looking heat shields under the car and push them up against the floor board and engine bay.

Finding something causing false knock can be a pain.
 
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Like Spoolboy said, a false knock condition can sometimes be caused by a rattle from a loose heat shield, etc.
 

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Discussion Starter · #7 ·

I went ahead and posted the video so people.can check it out. It seems loudest on the driver side. I DID find a manifold bokt that backed out, but we tightened it back down and have no changes to the issue. I have the motor apart now and I don't see anything glaringly wrong with the cam or lifters.
 

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The Bacon Hauler (‘12 Cop Charger)
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I was getting bad STKR and LTKR from the exhaust pipes making contact with the two crossmembers they pass over on the way back to rear of car. It was not audible to my ear at WOT, but I could sometimes hear it while at cruising RPM.

The resolution I settled upon was to buy a roll of that exhaust wrap (fiberglass?) meant to wrap headers with, and after soaking in water for a while I took both crossmembers off and wrapped them with the exhaust wrap.

The exhaust pipes can make all the contact they want now, the sound frequencies emanating from such contact isn’t picked up by the knock sensors and interpreted as knock anymore.
 

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Hey, all. I'm having a bit of a conundrum with some knock and funky ticking/ fluttering sounds on my 6.4. Last year I got some Kook long tubes and catless mids installed, along with solid motor mounts and a nitrous kit (which I really haven't used) and installed an email tune from a reputable tuner. Shortly after, I went on a work trip for about 8 months that I came back from about a month ago. Before I left, and about a week or 2 after I got back, the car drove and sounded great with zero issues. Then I started to see some consistent STK on my Trinity. Anywhere between 2-10 degrees between 2000-3500ish RPMs. At first, I went to the fuel as it had a quarter of a tank that had been sitting for a good while before I topped it off with fresh BP93. Still got knock, so I drained the tank, filled up with Sunoco 93 and a bottle of Royal Purple octane booster with no change. The car is making a a fluttering/ ticking sound, but only under acceleration and again, at 2k and up. We found a header bolt that had backed out quite a bit, so we tightened it back down and checked torque on all the bolts, but didn't see any soot deposits or any visual signs of a leak. At the same time, we did an oil change with Amsoil and an SRT filter. The car STILL makes noise and still picks up knock while driving and in neutral, albeit a little less. Also a weird thing to note, if I Rev in neutral and let off at around 4-5k, I can hear a pretty noticeable whoosh of air, almost like a turbo blow-off, so I'm still optimistic in thinking there's an exhaust leak somewhere the sensors are picking up. The only thing we haven't tried yet, short of opening up the block, is a stetho or smoke test. I'm hoping someone here has some input that can help me in the right direction before I start tearing into things I don't need to as I know longtubes are pretty notorious about resonating engine noise you normally wouldn't hear or notice. Thanks in advance!
First make sure engine is good by pulling the plugs and checking their condition. Then I would drop a bore scope down to see how the piston tops look. And finally I would follow up with a compression test. If all those are good you can confirm the engine is good and now focus on the exhaust. Anytime a bolt backs out there is a good chance the gasket is compromised so I would start by pulling the old out to inspect and then dropping in a good one. BTW what does your AFR (assuming you have a wideband installed) look like when you see knock? If it is a big enough leak that is audible you should see erratic AFR if the leak is upstream.

Oh and I would also check the bolts on the solid mounts to make sure everything is still torqued down.

Ah nevermind you have the motor apart already...talk about diggin in. So plugs looked good...pistons?
 

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The Bacon Hauler (‘12 Cop Charger)
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On the subject of false knock, i have found it is usually possible to differentiate KR that comes from false knock versus KR from spark knock when looking at the datalogs.

The appropriate PIDs have to be getting logged obviously, and knowing the specifics about how/where/when the log was recorded is beneficial (read: take good notes!).

If all that is available, I am of the opinion that if you are intimately familiar with your car and how it runs, and you are comfortable using your handheld tuner of choice (and it’s log viewing software), you should be able to tell when KR in a log is due to real knock versus false knock, and that will drive which direction the resolution attempts to go, obviously.
 

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Discussion Starter · #11 ·
First make sure engine is good by pulling the plugs and checking their condition. Then I would drop a bore scope down to see how the piston tops look. And finally I would follow up with a compression test. If all those are good you can confirm the engine is good and now focus on the exhaust. Anytime a bolt backs out there is a good chance the gasket is compromised so I would start by pulling the old out to inspect and then dropping in a good one. BTW what does your ARF (assuming you have a wideband installed) look like when you see knock?
I have a Wideband but no way to read or log it because the Diablo T2 EAS is junk and won't work. I'll be completely honest, these pistons worry me because they all look pretty dirty, but I'm also not sure what they're supposed to look like. Car barely has 18k miles on the clock.
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The Bacon Hauler (‘12 Cop Charger)
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Seems like a lot of carbon for only 18K miles. If whatever allowed that to accumulate has continued, you could be facing a situation where excess carbon in the CC has inadvertently raised the compression ratio, and thereby requiring a higher octane fuel than what your running.
 

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I went ahead and posted the video so people.can check it out. It seems loudest on the driver side. I DID find a manifold bokt that backed out, but we tightened it back down and have no changes to the issue. I have the motor apart now and I don't see anything glaringly wrong with the cam or lifters.
That sounds like a valvetrain issue (either bad lifter, lobe is worn, valve spring cracked or possibly valve seat dropped a little)...compression test would have help you find the piston as it would have higher/lower compression then the rest.
 

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Discussion Starter · #14 ·
So being it's been a while since I initially started this thread, I should mention I had the car stetho'd by a Hemi specialist shop and they pointed toward lifter issues, which is surprising as it's a non-MDS car. I pulled the motor apart and have a new MMX cam kit, including gaskets, pushrods, and new lifters sitting in the garage, but I want to keep digging in case the issue is something else. The rollers all moved fine, no signs of excessive wear on them or the cam. There was a few VERY small metal shavings on the OCV and a couple of the cam lobes, but nothing crazy and you'd have to look closely to even notice them. I also ordered a new set of header gaskets to replace since I already have them and the heads off. The ONLY other thing I can see that's super obvious is a missing nut on one of the motor mount heat shields as I had them swapped with the headers last year.
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That sounds like a valvetrain issue (either bad lifter, lobe is worn, valve spring cracked or possibly valve seat dropped a little)...compression test would have help you find the piston as it would have higher/lower compression then the rest.
I'll look at the springs and seats as that's one of the few things I haven't checked yet and I have a new set of springs to replace anyways. Thanks for the input.
 

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Did you ever do a compression test before tearing into the engine? As I read more I realize you really tore into the engine already but a compression test would have been my first thing to check.
 

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Unfortunately, no and I'm kinda kicking myself for it now. Right now I'm trying to decide if I wanna put the stock stuff back together and go back to diagnosing with it running or swap the kit in and go from there.
Yeah it happens. All the carbon buildup could have bumped up your CR but no signs of any damage. The rapid tap suggested valvetrain...if everything looks visually ok I wonder if a lifter plunger was pumped down/not holding fluid?

If you plan to reassemble, I would put in the lifter with larger rollers if the originals had the smaller ones.
 

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Discussion Starter · #18 ·
If you plan to reassemble, I would put in the lifter with larger rollers if the originals had the smaller ones.
I'll double check the part numbers on the ones that came in the kit. They should be same as factory since the car is a '17 M6. I'm starting to wonder if the Comp lifters would be a better option as well as they seem to be designed well based on MMX's tech video. I started panicking and suspecting rod bearings but I'm sure there's a lot more that I'm not seeing yet and I know the car sitting for 8 months with the same oil and barely and runtime is probably a huge factor.
 

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Post good pictures of the cam lobes and lifter rollers.

Also, did any of the lifters feel softer when compressing them?

The cam and lifter problems are not just limited to the MDS system and can happen on any lifter in any VVT engine. The pre VVT engines didn't really have many of these failures comparatively.

Your video sounds a whole lot like a lifter problem to me.

Is this also your car?
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Since you have it all apart, you can rotate the crankshaft back and forth and feel for any looseness in the bearings. Certainly not scientific or foolproof, but if a rod bearing is real bad you will feel it and may even see one of the pistons not move immediately as you rotate the crank. You may also feel binding or other things you would not be able to feel with the valvetrain in the mix.
 
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