davepl

I don't know if it's a chicken little thing, but I've started to see a lot of references to valve coking and theories that blame the direct injection.

I would imagine that keeping oil out of the air path (catch can) would help, but what about running a full bottle of Techron concentrate every 10th tankful or similar?

I don't believe much in "mechanics in a can", but it's a strong and well-respected detergent package. I wonder if it would prevent coking?

JHEBERT

The problem is that the fuel never touches the back side of the intake valve and stem....additives are almost useless. Meth injection, better yet, direct port injection methanol would help with this.

foreverfuelie

I saw this ad in my SCCA magazine. Thought I would give it a try just for grins. Baring a "media" blasting, I know of nothing else that would possibly clean the back of the intake valves that do not make contact with anything other than air, assuming the oil and contaminated vapors from the crankcase have been adequately filtered.

SUB VETTE

Keep the blow by oil and contaminants from entering the intake from PCV system and causing coking by using a catch can.

Ahmed_otb

if a catch can is the answer why didn't GM do it??

davepl

That's about the only way, though I'd be a little scared for my MAF. I don't know if we have an accessible PCV, but you can inject cleaner that way too.

jvp

Imagine how many people would remember to check their catch can on a regular basis. You can safely assume that percentage is: very small. Now assume the rest of the folks who don't check their catch cans suddenly find oil all over their garage floors on some random day.

Click here for GM's response.

Ahmed_otb

thnx

I just have had bad encounters with the catch cans and I don't want to go through it all over again

PLRX

I know there are many threads on this, but I started to wonder about this issue in 2012 when the C7 specs came out. I told many about it, and they responded with weird looks.

It's a fact, gunk will cover the intake valves faster than you think, and I have Seafoam in mind for preventive maintenance..

I can also try this one.

I'm no engineer, but an extra injector in the plenum would be great to run a "cleaning cycle". I'm pretty sure the PhD nerds would know how to design all necessary equipment to make it happen. Something like the wiper's washers.

PLRX

Well they designed one hell of a baffled valve covers, but that is not enough for the LT4s, and I've seen few videos on LT1s dirty valves.

There is plenty of proof, the supercharger gets soaked in oil without a catch can. I bought the catch can before The Phantom was delivered.

I'm waiting to warm up a little. Here is SoCal we are going thru a snow-less blizzard.

GOLD72

The only data point I can contribute is my nearly 6 year old 3.6L CTS wagon with over 73k miles. Coking of the valves due DI has never been an issue that I am aware.

davepl

I'm sure they tested well into the 200-300K range on these engines before deciding they would warranty them for 7 years (or whatever the emissions warranty is, which they'd have to cover).

I'll wait a few more thousand miles, pull my cover, and see what I see for oil residue. If there's any I'll likely do the Seafoam thing. More likely take it somewhere to have it done so I don't get arrested doing it in my own neighborhood!

SUB VETTE

All you ever wanted to know about using a catch can on the C7 Z06 and why:

https://www.corvetteforum.com/forums...ver-today.html

OnPoint

Perhaps one of the more interesting (to me) comments about catch cans on the LT4 lately was Katech saying they don't use them.

https://www.corvetteforum.com/forums...ity-owner.html

Snorman

Bingo.
I'll take Katech's input on this topic before that from a small vendor who is trying to scare owners into thinking they need one by posting unverified pictures of other makes and/or models with intake valve coking.
S.

Bad Dad

3 Z06ZR1

it's a nice theory but the catch cans are not all that.

Mine was letting oil draw through the can. Thus oil was coming in the power brake booster line.

SandmanAz

Pulled twice! My Z's system seems to function well.

dar02081961

Dave I understand your concern. We have all seen many threads and information about this over the years. The OEM's have addressed this issue. Many folks claim coking will be a problem many miles down the road after the OEM's warranty has expired. I guess that remains to be seen.

What I have been waiting on and have yet to have anyone answer is how much "coking" can a full synthetic oil create? AND if the car isn't burning any oil (very little oil between oil changes) how could there be much chance of coking to begin with? The truthful answer to those 2 questions will put your concerns to rest.

Bill Dearborn

As Tadge said in the other thread there may be some cosmetic buildup but they firmly believe it will not affect the performance of the car. Just because BMW has a problem doesn't mean GM does. They have installing DI engines in high volume cars for several years now and there hasn't been any howling from Polly Public about a problem. All it took was a few people with the old V6s and V8s in high volume cars to create a misplaced firestorm over Dexcool that is still going on 19 years later.

I believe Cosmetic means what it actually means, Cosmetic, looks bad but isn't, thus can be ignored and not worried about. Same goes for dirt on your license plate.

Bill