pgnielsen

I've read that C7s have an issue with oil drawing through the PVC valve back into the valve train causing carbon buildup. I've also read that connecting a "catch can" can resolve that issue. Is this correct?

angryBits

To be clear -- its not a Corvette thing, most cars, especially Direct Injection engines suffer from this.

FYREANT

Catch can helps. Nothing stops the buildup 100% though.

mustclime

crankcase and valve cover breathers would would stop it......PVC system is really just an emission control system. Of course you car would smell like an old school car.

FYREANT

You can stop the draw from the PCV but you cannot stop the carbon build up on the valves no matter what you do. Not unless you install a supplemental port injection system. I've got a breather tank setup on my blown C7 and have been catalogging carbon buildup for 52K miles. Valves look nasty still with the breather or without because it doesn't only come from the PCV draw..

pgnielsen

Thanks for the feedback. We plan on touring with our new Stingray and wanted to keep the glitches down to a minimum.

Bill Dearborn

Not that I have seen. Yes, we have some vendors saying there is a problem but GM has put millions of DI engines on the road over the last 10 years and they are not known for having a carbon buildup issue like the German cars have. Do a search for valve carbon build up on Google and you will find a lot of stuff but GM isn't mentioned much.

Yes, some people pull their LT$ supercharger lids off and show pictures of oil puddling on top of the supercharger but we really haven't seen any carbon issues. Even on the German brands that are acknowledged to have issues they don't show up until the engine has 65K or more miles.

If you are a typical Corvette Owner and drive the car 5/6K miles per year or less and plan on selling the car within 5 or 6 years a catch can doesn't make sense even if there was a carbon problem and the catch can actually worked.

Bill

dork

As I recall, GM will void your engine warranty if they find a catch can installed. Your dealer might let it slide and not care, but if work is done and a regional service representative does an inspection for approval, s/he'll void the warranty and block it from further claims. There's plenty on this forum about the subject. A lot of guys plan on R&R'ing the OEM tubing for the catch can before taking their c7s in for service so's to stay within warranty "standards".

davepl

Kind of a dumb question, but bear with me:

You can buy concentrated bottles of Techron that are intended to be poured into the tank, but that does us no good. Is it a strong enough detergent/solvent that it could be sprayed into the airstream? I realize it's not magic.

If we had a good shot at the valves (we don't because of the IC bricks) you could spray it right onto the valves and let it sit, but that always runs the risk of loosening a chunk all at once too, I suppose.

But I don't know if it's strong enough to do anything useful via a topical application like that.

FYREANT

Could it work? Sure. Would I risk it? Nope. Like you said you could loosen a big chunk. I would simply pull the intake manifold and clean the valves by hand as much as possible every 20-25K, buts thats just me.

David@MMS

you can use a top end cleaner like seafoam and hook to a vacuum line and hope for some sort of uniform distribution, there is no way to tell that you actually did any good without an actual inspection or maybe before / after datalog, dyno.

knowing that you stopped pcv oil from contributing to the problem is always a good feeling

Maxie2U

I wonder if products like these really work or just hype?

http://seafoamsales.com/sea-foam-off...-port-and-gdi/

http://www.crcindustries.com/product...-oz-05319.html

https://www.bgprod.com/catalog/gasol...ction-cleaner/

djnice

Has anyone installed a catch can on the 2017 GS? My results are troubling me. The can is catching a clear liquid that seems to be fuel and moisture. Not really any oil. Did GM change something? Is it possible this liquid is helping clean the intake valves and catching it will actually do harm?

David@MMS

its the pcv system job to remove dirty fumes from the crankcase. if for you that means more condensation than oil then it is what it is.

i see it all sorts of ways.

also depending on the system you have setup it could be keeping oil from getting to the can as much as usually runs through the stock system

djnice

I suppose, but what I am catching seems more like a solvent. It evaporated relatively quick from the jar too. I installed a different setup to test it some more.

David@MMS

i would not modify the connections without direct consultation with your catch can manufacturer. engine damage could result.

what is caught as i said varies depending on the car, how the engine is built, the driving environment, the fuel used, and the application in general. ive seen it from crystal clear water looking to brand new pure oil looking, to coffee (light and espresso)

Maxie2U

The stuff my CC collects looks like really dark motor oil which is burnt carbon.

djnice

That's how it is with my LSA, but not the LT1. What C7 is yours from? I switched my LSA setup to the LT1, but haven't had enough roads miles yet.

tiborrules

I have a 15 z51 with a procharger and catch can. I have heard that running a fuel additive can help with carbon buildup. I am running a bottle of chevron with each tank. Has anyone checked to see if additives actually help carbon build up?

Maxie2U

Nope, fuel additive will be of no help. As stated in an earlier post the fuel injectors are in the engine cylinder so no fuel sprays on the intake valves hence the carbon build-up. And that is why people install catch cans.