johnodrake

General Motors unveiled the new 2023 Corvette Z06 in October of 2021, ushering in the next level of performance for the eighth-generation C8 Corvette lineup. The main party piece in the 2023 Corvette Z06 is the new naturally aspirated 5.5L V8 LT6 gasoline engine, however, some customers complain that their LT6 makes a loud ticking noise. Now, GM is issuing a fix for this issue.According to General Motors, the issue can manifest as a ticking, tapping, or snapping noise from the engine on some units of the 2023 Corvette Z06. It’s unknown at this time how many units may be affected.

GM notes that the LT6 incorporates a mechanical valvetrain design and does not use traditional hydraulic lifters. As such, some mechanical ticking noise from the valvetrain is normal. However, the noise could become excessive and not periodic, which may be the result of misaligned camshaft caps.

The ticking noise may be heard when the engine is idling, and could become more noticeable with the rear engine hatch open and the vehicle in Tour mode. In addition, the noise may become more audible as the engine warms up to its normal operating temperature. A GM technician will use a PicoScope to verify the noise concern, both before and after the realignment procedure is performed.

GM To Fix 2023 Corvette Z06 LT6 Engine Ticking Noise (gmauthority.com)

Redc8z06

I also heard depending on which side of the engine the noise is coming may or may not require the engine to be pulled.

Found it in the TSB:

Important: If the noise is heard from the left bank, the camshaft cap adjustment procedure can be done with powertrain in vehicle. If the noise is heard coming from the right bank, it will be necessary to drop the engine and transmission assembly to gain access and remove the camshaft cover for the adjustment procedure

AustinVetter

Wow. I will not own this car without a warranty.

Jridden

If its your right bank then you're outta luck it seems.

Panfish

Happily still waiting for my car to dodge as many bugs as possible. Hopefully, they’ll soon nail down the apparent transmission issues too many are talking about.

ZR-1DUDE

Do we know if they are all impacted?

D.

SharkDiverZ06

Four years in now and no meaningful progress...Good luck with that!

Z0HS1CK

Damn. Oh well that's what the awesome GM 5yr powertrain warranty is for! lol

Number 9

It’’s my understanding that not all are impacted. Some people are claiming theirs doesn’t tick.
I’ve gone to a couple car events recently hoping to see another Z I could listen to, just to compare. So far no luck.

Higgs Boson

So far mine has no tick or leak, #599

Doesn't mean it won't do it at some point I guess. Not too worried about it.

mfain

Repeat post from the LT6 engine failure thread above. Just checking to see if anyone can answer the questions about factory cap torque process.

It would be interesting to track VINs on cars with the problem. What was the highest VIN (latest build) to experience the problem? That might give us an idea of whether or not the issue was addressed on the assembly line. Is anyone with the ticking issue willing to post the last 4 of their VIN, or the date of manufacture? Does anyone know for sure how the cam caps are torqued during original assembly - manually or machine? Reading the TSB they state that loosening and retorquing the caps "realigns" them, yet the procedure states "Do not remove or physically try to shift, wiggle, or adjust the cap seating". This seems to indicate that the cap torque was the issue, not necessarily alignment.

Edit: After further review of the TSB, I offer the following opinion. I believe the TSB is a cosmetic fix for a superficial problem.GM is offering to correct the "ticking" problem to appease customers who are offended by the noise, not to prevent future failure of the subject LT6. In the TSB GM notes the following: "Before performing any repair on the left or right side of the engine please review the realignment procedure with the customer and ask them if they want to proceed with the repair." If GM identified a problem (ticking) that could potentially result in engine failure, I doubt they would give the customer the option of not doing the repair. As far as I can tell after reviewing the early engine failures (videos have since been removed), the failures did not occur after a prolonged period of "ticking". They were characterized by a rapid onset of loud ticking, followed by louder noises, engine shutdown, codes indicating misfire on one bank or the other, and often the inability to turn the motor over for restart - a sudden, acute failure. From a purely speculative standpoint, a cam cap failure, whether it be failure of the cap itself, loosening of improperly torqued cap bolts, or failure of a bolt due to installation over-torque would probably result in the now unsupported portion of the cam flexing, potentially resulting in valve train noise and camshaft failure. Have you ever dropped a camshaft on the floor, intentionally or otherwise, and observed how easily in snaps in half - cast camshafts won't take unsupported side loads.

okaythen

Sounds like GM doesn't exactly know what's the root cause of the ticking noise?

Well my allocation is up, I am in the mid 300s and I got the allocation now, I heard there are constrains on Z06 and aero but is it also the engine ticking that a lot of people are deferring? There are so many people in front of me! I was expecting to get the allocation in 18 to 24 months and not so soon. Do you guys recommend me to wait until GM can fix the problem? Or go ahead with the purchase? Thanks for the help guys

capevettes

My order was accepted last week. I won't be deferring. This is affecting a small percentage of Z06'S, and since they are aware of it, will likely affect fewer going forward. I have only heard of people deferring orders due to constraints.

23/C8Z

when they were revealing this engine to the public they tried very hard to slip hints about noises and vibrations that will be felt and heard with this setup and over and over again reminded people that these inherit traits if this fpc and no lifter setup would be a new experience and create those assumptions of something isn't right but that in fact it is.

We are seeing how the smooth sbc crowd is handling this race car engine in their beloved corvette.

I saw a guy with an earlier build vin 0621 and he heard my engine vin 3551 and he said now listen to his and his was noticeably loudly ticking from left side vs mine with no audible tick (he has 3200mi i had 600).

I told him i would just drive it and enjoy it and if it blows up get it fixed. you can't live in a world of impending doom. Why get up in the morning?

If gm was worried about it you would never see a tsb with wording like that.

okaythen

Thanks guys that was very helpful.

Sounds like it's just a small percentage of z06s and no serious issue yet, will go ahead with the order. Have a good one now.

Redc8z06

Maybe they don't maybe they do know root cause since they know what needs to be done to fix it so I would have to believe they ether change or created a new procedure at the plant to check and and/or correct any motors they are building today.

I would not wait.....

23/C8Z

it's not a "fix" it is meant to quiet the noise down some.

But after all the reading i did on it it sounds to me like it is equivalent to the old piston slap issue from way back when. You could put 100k or more on an LS with slap and it still runs fine. Just some cosmetic wear on the one side of the sleeve but they can make a racket. So they're trying to get ahead of that type of scenario.

If it makes enough of a racket they'll replace (hence the pico scope testing).

At least one person i read about had it done and the noise was there but less and sometimes louder.. new pico test showed it was cut dramatically. They gave him the option of fixing again or leaving for now.

It's going to he an inherent trait on this LT6. As long as they aren't blowing up from it? So be it.

Redc8z06

Well a lot of us are heading to Carlisle this week and a lot of GM engineers will be there so I will try to remember to ask them about it.

23/C8Z

I will be there with mine as well. I'm sure they'll be overloaded with this very question 😂

GrandSport 2017

So, the root cause is a flawed lash setting procedure.
The symptom is excessive noise from the valve lash being too loose.
The fix is tightening up the valve lash.

Improper cam cap alignment is nonsense Its aligned with dowels, and would not cause excessive lash no matter what axis it was shifted even if it could be shifted enough to cause one of the below problems.
A longitudinal shift wouldn't do anything but tighten the cam end-play.
A shift on the load axis would cause a reduction in journal clearance and potentially cause galling on the cam journals.
Neither of which would reduce or increase valve lash unless excessive journal or bearing surface wear became an issue, and then at that point the engine would need new heads and or cams.

The fix is basically checking and adjusting the valve lash back into spec.
It sounds to me like GM doesn't want to admit that the fancy valve lash setting procedure they were so proud of touting and claiming was so fool proof has issues.

The good news is its not wear.
Also, if its not a problem very early on then its less likely you will have this issue from the factory adjustment procedure.

With that being said, they may be adjusting valve lash an more early production LT6 engines in the coming years then originally planned for.
Also, I could almost guarantee they are final checking lash by hand on these engines from now on.