Are catch cans necessary?
08-09-2018, 10:18 AM
#1
Instructor
Thread Starter
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?
08-09-2018, 10:21 AM
#2
The following users liked this post:
boofus1 (08-09-2018)
08-09-2018, 10:52 AM
#4
E-Ray, 3LZ, ZER, LIFT
Member Since: Sep 2007
Location: NE South Carolina
Posts: 29,477
Received 9,619 Likes
on
6,625 Posts
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! 
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!"
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!
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!"
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!
Last edited by JerryU; 08-09-2018 at 10:55 AM.
The following users liked this post:
boofus1 (08-09-2018)
08-09-2018, 11:10 AM
#5
Instructor
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!
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!" 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!
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!"
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!
Keeping the gunk off the top of the engine is nothing but a good thing.
08-09-2018, 11:13 AM
#6
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.
Last edited by Foosh; 08-09-2018 at 11:17 AM.
08-09-2018, 11:27 AM
#7
Team Owner
Member Since: Jan 2007
Location: cookeville tennessee
Posts: 28,846
Received 1,762 Likes
on
1,529 Posts
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.. 
Robert
Robert
08-09-2018, 11:40 AM
#8
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.
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.
Last edited by Foosh; 08-09-2018 at 12:10 PM.
08-09-2018, 12:07 PM
#9
E-Ray, 3LZ, ZER, LIFT
Member Since: Sep 2007
Location: NE South Carolina
Posts: 29,477
Received 9,619 Likes
on
6,625 Posts
Just to set the science straight, no gasoline goes over the back of the hot intake valves in a DI engine! That is why, unlike port injection or a carb, gas with “cleaning additives” washed all of the PCV oil, oil mist and “combustion products stuff” from the backs of the hot intake valves before it had a chance to bake-“coke.” There are also small oil particles that form when exiting the crack and rod journals and hit the spinning crack contacting the very hot underside of the pistons and oxidizing.
All that “stuff” exits the PVC valve and small PCV hose from the crackcase to the intake manifold. It never sees any gasoline before it hits the back of the very hot intake valves. One can “wish” GM has a magic solution and not consider the effort placed to improve the PVC system on the new dry sumps to reduce the amount of oil leaving the crackcase and staying in the crackcase. Folks can also “hope” that Tadge’s statement that the coking that does develop is “only cosmetic.” Similar to accepting that the increased Grand Sport and Z06 wheel breakage is just normal and only due to folks hitting potholes. Be happy to post that Tadge Answer forum post as well, but it won’t make your bent wheels any better!
Bottom Line, never used a “catch can” on my ‘88, ‘93 or 2008 C6- with their port injection, didn’t need one. I added one on my 2014 C7 Z51 and removed when I sold it and installed on my Grand Sport.
We can each have an opinion, and do as we wish.
All that “stuff” exits the PVC valve and small PCV hose from the crackcase to the intake manifold. It never sees any gasoline before it hits the back of the very hot intake valves. One can “wish” GM has a magic solution and not consider the effort placed to improve the PVC system on the new dry sumps to reduce the amount of oil leaving the crackcase and staying in the crackcase. Folks can also “hope” that Tadge’s statement that the coking that does develop is “only cosmetic.” Similar to accepting that the increased Grand Sport and Z06 wheel breakage is just normal and only due to folks hitting potholes. Be happy to post that Tadge Answer forum post as well, but it won’t make your bent wheels any better!
Bottom Line, never used a “catch can” on my ‘88, ‘93 or 2008 C6- with their port injection, didn’t need one. I added one on my 2014 C7 Z51 and removed when I sold it and installed on my Grand Sport.
We can each have an opinion, and do as we wish.
Last edited by JerryU; 08-09-2018 at 12:17 PM.
The following users liked this post:
boofus1 (08-09-2018)
08-09-2018, 12:13 PM
#10
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.
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.
Last edited by Foosh; 08-09-2018 at 12:19 PM.
The following users liked this post:
4thC4at60 (08-09-2018)
08-09-2018, 12:23 PM
#11
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.
The following users liked this post:
boofus1 (08-09-2018)
08-09-2018, 12:48 PM
#12
E-Ray, 3LZ, ZER, LIFT
Member Since: Sep 2007
Location: NE South Carolina
Posts: 29,477
Received 9,619 Likes
on
6,625 Posts
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.
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.
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!
TO EACH THEIR OWN!
08-09-2018, 12:55 PM
#13
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?
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?
Last edited by Foosh; 08-09-2018 at 01:18 PM.
08-09-2018, 12:55 PM
#14
Race Director
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!
TO EACH THEIR OWN!
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!
TO EACH THEIR OWN!
08-09-2018, 01:06 PM
#15
Team Owner
Absolutely not needed.
08-09-2018, 01:13 PM
#16
E-Ray, 3LZ, ZER, LIFT
Member Since: Sep 2007
Location: NE South Carolina
Posts: 29,477
Received 9,619 Likes
on
6,625 Posts
Some of us have built engines, my latest is the 502 crate motor in my Street Rod. When I was 16 built a bored out Olds for my first car, a '41 Ford coupe. In the interim saw NASCAR engines and heads disassembled at Level Cross NC when we were a sponsor for Richard Petty!
This is what my 502 cid engine CNC port matched intake passages looked like in my garage in assembly! The gas from that 850 Holley "double pumper" keeps them looking relatively new!
Your car your choice!
Last edited by JerryU; 08-09-2018 at 01:23 PM.
08-09-2018, 01:19 PM
#18
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.
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.
Last edited by Foosh; 08-09-2018 at 01:23 PM.
08-09-2018, 01:23 PM
#19
Le Mans Master
Member Since: Jan 2006
Location: Down south in Dixie
Posts: 6,801
Received 2,639 Likes
on
1,702 Posts
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.
08-09-2018, 03:45 PM
#20
E-Ray, 3LZ, ZER, LIFT
Member Since: Sep 2007
Location: NE South Carolina
Posts: 29,477
Received 9,619 Likes
on
6,625 Posts
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!