Are catch cans necessary?
 

I keep hearing about catch cans on the C7's. Are these absolutely necessary? What harm can come if I don't install one?

None
 

None - the car did not come with one.

Had one on my 2014 Z51 and was collecting ~1 oz of oil/1000 miles. That's one oz that did not pass over the very hot intake valves and cause "coking" - i.e. baked on oil on the back of the valves. Tadge says it's "Only Cosmetic." Perhaps not a significant power detractor but some of us are more OCD about the inside of the engine that the outside. I could care less about fingerprints that come off when I wash the car! Don't want to clean the backs on intake valves! :lol:

Also GM have spent a lot of time and engineering effort "improving" the PVC system in the new dry sumps as I have in my Grand Sport! Doubt they did that for "no problem!" :yesnod: I took the "single outlet can" from my 2014 Z51 and put it on my Grand Sport. I now collect only ~1/2 oz of oil that does not go past the hot intake valves.

Would I buy a can for the new Grand Sport? Don't know that I would. However IMO it can't hurt.

For those that fret about possible warranty issues etc don't do it. I don't-had no issues with my 2014 nor do I expect any with my Grand Sport. The argument of why GM (or other manufacturers) don't add one is not rational IMO! Folks don't check their tire pressures or oil level as recommended. Most would not check the "can" and empty the collected oil. If you don't empty the "can" periodically and dump the collected oil it could cause problems. Then were would the none-DIY owner dump it? In the drain? Don't think that would be recommenced by GM! I dump mine in the container I use when I change my oil. That gets dumped at that time in a recycle center.

TO EACH THEIR OWN!

Good perspective on the issue. I think every car should have one.. but hadn't really thought about the masses that would fail to check and drain the can as needed.
Keeping the gunk off the top of the engine is nothing but a good thing.

Completely unnecessary. This has been debated ad nauseam, and no one can provide any credible evidence that they provide any meaningful benefit. They do make some people feel better, and if it serves that function, then I suppose there is that benefit.

ttt
 

You will have guys that say yes & then others that will say no. I do have one on car I say this if it catches any at all & if you put one onto your car it will do so. That is that much what ever that amount is that didn't get coked onto the valves & down into the intake. You can do it are not do it that is your choice.. :thumbs: Robert

There is no credible evidence that whatever you caught would otherwise get "coked onto the valves" and cause any more coking than pure gasoline combustion. Whatever tiny amount of oil that may enter the combustion chamber is round-off error compared to the amount of gasoline ignition, which causes valve coking too. Between 5-7K oil changes, most LT engines show almost no oil consumption.

Like I said, it does make some people feel better. Sugar pills make many people feel better too. As sure as the sun rises in the east every morning, someone here will soon post a picture of coked valves, but they can't demonstrate a catch can would have prevented it.

Yes, Jerry, but that's irrelevant to the argument. You repeat the same argument over and over, which is completely missing the point.

Gasoline combustion causes coking, and the amount of that is exponentially larger than the tiny amount of oil ever entering the intake chamber. There is no proof that it's primarily or even detectably caused by oil. That's purely shade-tree speculation by amateurs.

Catch cans are toxic to your GM warranty. Funny, GM telling c7 owners we'll be just fine with no worries about carbon build up on the back of the valves from direct injection not sending detergent gasoline to wash buildups off....then GM: 1) reducing the powertrain warranty on 2016 and later models to 60,000 miles from the previous 100,000 miles coverage (performance reduction from crudded valves allegedly starts showing up at 60,000 miles)....and 2) making a running change to the C7 motor by ADDING port injection in conjunction with the direct injection on the 6.2 liter used in the 2019 ZR1. So ZR1's get their valves washed by detergent gasoline, other C7's do not.

Yep and you keep trying to confound the issue by bringing up gasoline that I know you understand does NOT touch the back of the intake valves where coking occurs! However some of the silent majority that view these threads might not. Just have to look at the BMW and Ferrari high performance engines that used DI well before GM. They had NO gasoline passing over the hot intake vales and BMW suggested walnut shell blasting to maintain performance at ~50,000 miles. Yep coking occurs from PCV "stuff" not gasoline with "cleaning additives.

Until I see the "magic solution" GM is using versus BMW, Ferrari etc that express concern about coking I don't believe one is "foolish" to add and also don't believe it is harmful for someone who empties it periodically and dumps the collected "stuff" as is required. Does it catch everything -NO! Is it cheap insurance-YEP, IMO!

As I said, for those afraid of the warranty issue-don't add one! But don't think that solves the problem!

My guess is the new C8 engines will have one of the solutions used by Toyota, an engine with both DI and port injection. Even the ZR1 has that but primarily for the extra power. Expect it can be designed to work periodically to wash the PVC "stuff" off before it bakes on the back of the intake valves. Another solution is to get the EPA to agree we could dump the "stuff" on the ground as we did prior to the 1960s! Had one on my 1956 Chevy V8 and my prior 1950 Ford V8! Not a good idea! :lol:

TO EACH THEIR OWN!

Jerry,

To amplify my above points a little further, the backs of DI engine valves in the LT engine are exposed to the combustion by-products of 44,800 ounces of gasoline in a 7K mile period between oil changes (assuming 20mpg combined). And yes, we all know the backs of the valves are not getting washed as they would be in port injection systems. By contrast, in my two LT engines, the oil level has remained essentially the same between changes with no detectable oil consumption, so let's assume a worst-case scenario that 4-6 ounces of oil is entering the combustion chamber during that period. That's probably a significant over-estimate.

So let's see, the backs of those valves are exposed to 44,800 oz. of exploding gasoline by-products without getting washed, and maybe 4-6 oz. of exploding oil by-products, and you're really going to conclude that adding a catch can is going to prevent valve coking?

If coking comes from pcv oil then why doesn't the intake port get coked up ?

Absolutely not needed.

Lol .. ok Jerry.

LOL, ok Jerry.

The combustion by-products of gasoline, and lots of it, are MOST CERTAINLY touching the backs of the valves. You are the one either missing or purposely confounding the issue.

boofus, I had to laugh. Not at you, but at the question. It's like asking, should I get "black or chrome wheels", "manual or automatic", or "does the jeans make my butt look big". The best suggestion I have is if you want one for the peace of mind then by all means yes, you should get one. We're just going to confuse you with the answers we give. :yesnod:

It's like the old Duck question! The stuff I and many other's collect looks like oil, feels like oil and smells like oil! Let's hope what is in the crackcase isn't that much blowby as it is oil mist, burnt oil particle from the oil leaving the bearings in the crack main and journal bearings and hitting the bottom of the very hot pistons as well as fine "oil" particles.

The LT1 also has oil squirters that spray oil on the cylinder walls under certain conditions. Sure there is some water and other combustion gases, which is why I call it "stuff." All I and those that add a "can" know is we're catching some of that "stuff" and dumping it! It's stuff that does not have a chance of causing coking!