There is no evidence that they are functionally beneficial because there is no evidence of a problem on LT engines. I personally know of 2 over 100K mile C7s that had no significant valve deposits when they were partially disassembled for valve spring replacements. Neither had catch cans and the only service was normal oil changes.

In 5 years in the C7 section, I don't recall a single report of valve carbonization requiring service.

They do collect small amounts of oil, which seems to make a lot of folks feel better, so perhaps they do provide a psychological benefit. However, there is no evidence that small amount of oil was problematic in engines where it was not collected.

 

Does this void your warranty?

 

Tadge Juechter said at one point it was unnecessary and could put a block on the engine warranty. Many who had them removed them before service.

 

Why would it void the warranty? C8 owners have been showing there cat cans with a sizable amount of oil in them.

 

If you have an engine problem requiring dealer warranty service, GM can deny the repair if you've made any modifications to the engine. They don't care if oil is being ingested into the intake, since it's by design and you're modifying a system on the engine.

 

GM can not control the quality of catch cans MFG, if they fail by sending debris into intake, or cause pressure build up...it could cause engine damage. That's why they would claim to void the warranty.

 

That is why if you decide to buy one, buy from a reputable catch can manufacturer.

 

Sizable, no. I would call it a negligible amount. 007 answered your warranty question.

However, the more relevant point is that there is no evidence of a problem in LT engines. Also relevant is that there is no evidence that catch cans actually prevent the problem in DI engines that are prone to valve deposits.

As I said, they do make a lot of people feel better. If you're one of those people, go for it.

 

So horse power obsessed had that much in 4K miles and that is negligible....

 

For example one manufacturer with a 2 outlet Catch Can, where a check valve is needed, had it installed backward! That would cause GM to say it would void a warranty. Also you have to drain the oil from the can- if you don't that could cause a block of the PCV system and GM might void a warranty! Installed and managed properly, I'd defend it's use.

I'll add my $0.02 to the discussion, since I added one to my 2014 Z51, measured the volume of oil and "stuff" collected, for 3 1/2 years. Then spent a lot of time and instrumented my 2017 Grand Sport defining the major change GM made to the PCV system to determine if adding a "can" would it do any harm. The answer was no harm! BUT I collected 1/2 the amount in my one outlet can. I've considered my C8 and decided in my street driving with WOT being a small percentage it's probably not needed and I won't add.

In fact since I have actually used a catch can, tested and instrumented my 2017 Grand Sport I'd say my $0.02 is more like $0.10! I chuckle at all those who said it was not an issue in the 2014 and 2015 and believe what Tadge said it's "mostly cosmetic" BUT GM spent a lot of engineering time and effort in building a better system for my 2017 GS for the non existent problem! They no doubt spent more time designing and testing on the C8.

It's a complex discussion and can't be summarized in a post. If you thinking about adding a quality catch "can" to your C8, my ~20 page PDF with lots of pics is worth a read:
http://netwelding.com/Catch_Can.pdf

My Grand Sport PCV System is much more complex than my 2014 Z51 Dry Sump. Many more lines and internal baffles.

I used this vacuum/pressure gauge to define how the two hose system going to the air intake in the 2014 dry sump was replaced with one! Where did the fresh air that needs to replace the PCV "stuff" come from? Found out!

 

Yep, given those few ounces accumulated while 200 gallons of gasoline also combusted in 4K miles.

Again, there's no evidence of a problem in LT1/2 engines. If it's a problem, we should have seen some evidence by now given all the LT engines out there since 2013. It was very evident in other DI engines relatively early on.

But, the icing on the cake is that there's no evidence that catch cans would have prevented valve deposits in those problematic engines either.

 

1000 miles with my catch can (clearly not my hands).

 

So what? That's not evidence of anything other than a little oil in a can.

However, as I said, if you makes you feel better, keep collecting. Feeling better is good.

 

I see that you've been on the forum for long time and have many posts, I feel sorry for the people that have read them.

 

After all the posts I have read, I am going to hold off installing the catch can until after the warranty is expired. It may potentially impact an engine warranty claim (which I think is quite slim).

Once the warranty is expired, then I may decide to add one. Who knows, by then there might actually be a consensus (or at least more data) on if the can is needed for this engine.

 

The “deniers” refuse to address the fact that GM put a lot of time and effort in improving what they say was the nonexistent "coking" issue in 2014/2015 Z51’s to provide significantly reduced oil going into the intake in the 2017 Grand Sport! Yep quote Tadge statement "it’s mostly cosmetic!"

Of course some believe even Tadge's marketing speak like the reason for no standard shift is “no clutch pedal room" or "can’t cut a hole in the center support structure but have NO answer to what GM was supposed to do with the law that would have gone in effect in 2017 and by 2025 required the Corvette family to get ~40 mpg!

Bet the person who wrote this press release has been sitting in the wings just waiting is now ROFL!

https://obamawhitehouse.archives.gov...iency-standard

Note: it says the average car will require 54.5 mpg BUT the 1174 page government report it’s based on shows the Corvette family would ONLY need ~40 mpg! Yep that requires most C8's to be hybrids! That is what GM had to plan to achieve!

 

I am just posting in here to inform the group, not to drag up and out an old argument.

Earlier I posted about maybe using Seafoam Spray as a tool to help clean out the top end of a DI engine. I finally did the procedure on my ‘16 Camaro with 15k miles on it. It took about 30 mins total from prep to execution. 5 min prep, 5 mins to install the spray nozzle properly. 10 mins to spray while one runs the car at 2000 rpms. You end with a suggested ten min drive, during which spirited acceleration is recommended. The first acceleration I did a crap load of fog came out the exhaust as expected. I have no idea if it cleaned out the valve stems, I’d need a scope to confirm, but for a front engine car it was pretty easy to perform the steps. I am also sure on a 15k mile car there wasn’t much in deposits. This is all preventative maintenance on my part.

I wonder how much harder or impossible it will be to perform this procedure with the C8 with the way the air box meets the TB and the need for a person to stand there and hold the can while spraying into the TB.

 

^^^
Will be interested in a fiberoptic comparison if you have base Pics. Recall Ferrari was reportedly planning to have their DI cars done at the dealer with a "cleaning system" around 2014 when I got my C7 DI. They and BMW had high performance DI engines well before GM. It's the hot intake valves in a high performance engine versus a DI "grocery getter" that apparently cause more "coking." The large single valves in a Vette are even more of an issue than two smaller intake valves in a Ferrari or BMW which have a shorter cooling path to the valve seat where much of the cooling occurs.

However it was later reported that once baked on the deposit cannot come off with chemicals (or at least much) and that is why BMW went to walnut shell blasting at 40,000 to 50,000 miles.

 

Yeah I should have thought about grabbing a before pic, and in any case I barely put 3k miles on this car per year, so by the time I trade it in next year, I won’t be doing this procedure anyway.

Maybe I can still get a scope at least and get a pic of the current state after the procedure. BUT I also don’t want to take the damn engine cover off the Camaro a year away from trading in. Apparently its a pain in the *** to reinstall the cover and I don’t want to mess with a mostly stock car so far. Maybe I can snake the scope through the TB and find the valve stems....

 

It would be nice if single data points could provide compelling evidence, but then there would be evidence that sugar pills and saline shots cure myriad horrible diseases.

We knew fairly quickly that certain Audi, VW, and BMW gasoline DI engines had a problem, but catch cans weren't a solution there. There is no such evidence from GM.