COSPEED

Have several threads on the intake valve coking issues with the LT4, so will make this one for the LT1.

This video does a good job of showing you what the issues are, the causes, and better understanding your new generation engine and how to prevent issues down the road. Look close and pause the video several times to see just how rapidly the intake valves are building the deposits.


I recommend the crushed walnut shell blasting media service but the manual cleaning as shown will also work.

Now, much of this is redundant if a member searches, but I will cover it all here for the C7 crowd in one thread.

Prior to 2014, all GM V8 gasoline engines were port injection. This constantly showered the intake valves with detergent fuel (ALL gasoline in the US must have minimum mandated detergent content to keep valves clean from back prior to port injection when carbureted engines experienced this coking causing wear to valve guides and stems resulting in a needed valve job by 40-50k miles) and when the industry migrated to the port fuel injection most have grown up with valve jobs went the way of the dinosaur, that is until GDI came onto the scene to be able to meet Federal emissions and CAFE fuel economy standards. So, here is a diagram of how a port injection fuel system kept your intake valves spotless longer than the life of the engine, and why most do not remember when a valve job was part of owning a car:



This fuel spray kept the valves cool and clean and even after 100-200k miles, a port injection engines intake valves will never have deposits on then, and therefore the valve guides and stems rarely saw wear (unless a machining error as the LS7 is known for in some instances) and the main reason for a "catchcan" was to stop the oil ingestion that caused detonation, clogged ringlands, and other issues, but never contributed to premature wear of internal engine parts and the degradation of power and economy over time like we see today with GDI.

Below shows how now, top tier fuel does nothing to improve any part of the injection or fuel system, and the fuel never touches the valves:



There are many advantages to GDI vs PFI, and this is mainly due to the near elimination of detonation (pre-ignition, Knock, etc.) as the fuel no longer is present through the entire intake and compression stroke where any glowing carbon spec or hot point in the combustion chamber could pre-ignite the A/F mixture. Now the fuel is not introduced until the final 10% or so of the compression stroke, and it is present only milliseconds (most of the combustion process occurs before the fuel can even touch the piston top) so we can now see far higher compression ratios, lower octane fuels, less emissions, and better fuel economy. The fuel injectors now operate at 2000 plus PSI vs the 45-55 of old PFI, so they cannot easily form ANY deposits. This renders any fuel additives, top tier fuels, etc. useless and a waste where they were of great benefit to the PFI engine.

The downside is with no fuel to keep the valves cool and deposits free, we now have a far greater issue that back in the 60's and 70's when carbureted engines had the coking and wear issues from it. AT least then some fuel cooled and cleaned/slowed deposits. Now there is zero.

So, a valve that would have looked like these pictures of a PFI engine at say 142000 miles (actual mileage of the LS engine in these pictures):





now will look like this in as little as 40k miles:


And the deposits are not like the soft carbon build up on piston tops of PFI, these are hard crystallized very abrasive deposits that are pulled into the guide with every cycle of the intake valve causing premature wear far greater that back in the carbureted days. Look close at how the stem suffers as these deposits wear on it, and the guide is the softer of the material:


These deposits are caused by more than just the oil mist present in the intake air charge, there is also several other damaging compounds that enter the crankcase as blow-by, and what you see is only part of the issue. Over time, as these hard abrasive pieces break loose, smaller ones can be forced between the piston and cylinder wall causing scouring and larger ones can get trapped between the valve and seat causing piston to valve contact and a bent valve or worse:



Look closely at the valve above, and you can see on the left portion of the stem where the tulip meets a large chunk broke off and caused the damage. The owner bringing the car in to the dealer they did diagnose it right away so a good amount of driving was done after this occurred and you can see the additional build-up over where the chunk broke off.

Now, anyone with a 2014 or 2015 LT1 have doubts this is occurring in your engine? It only takes 5-10 minutes and minimal tools to remove your intake manifold and look at YOUR valves up close and see the severity at the miles you have on yours.

Now, how to prevent this?

The "catchcans" of the past that worked well with a PFI engine, only trapped 15-50% or so of this oil mix that bakes onto the valves so they may slightly slow the coking, but will do little to stop it. You must use one of the very few that catch and trap 95-08% of this mix, and those are true air/oil separation devices. ColoradoSpeed and Elite Engineering having two of the most effective period currently on the market (extensive test results available to any that wish to see how the other "catchcans" stack up).

You must stop as much of this as possible.

Now, looking around I see several well intended solutions, that are not well thought out, and the most common is to delete the PCV system, and just rout your clean and dirty side lines into a tank with breather, or worse, open hoses near the ground (where one due to the Venturi effect will suck up dust and dirt directly into the tank and the engine).

The PCV system does far more than satisfy emissions. Back when the Fed mandated the PCV system in the mid 60's, it was rare for an engine to go much over 50k miles before excessive wear of all internal parts resulted in an entire rebuild being needed. And even though the PCV system was mandated for emissions alone (before that draft tubes were the norm, similar to the breathered Tanks seen today) but it did not take long for the industry to see these same engines were going 100-150k plus miles with little internal wear. Studying this found that the PCV system was constantly removing the damaging combustion by-products from the crankcase as soon as they entered and were still in a gaseous state. If allowed to settle, these mixed with the oil contaminating it and causing wear and failure eventually. The PCV system was removing these allowing the oil to stay cleaner longer, and the damaging compounds to accumulate at a minimal amount. So, defeating your PCV system is a sure way to cause a shortened engine life and accelerated wear. The compounds causing this wear and damage are as follows:

Water vapor

Unburnt fuel

Abrasive soot and carbon particles

Sulfuric acid, and more.

70% plus of internal engine wear is caused by the particles in the 2-5 micron size, and as your oil filter can only trap down to 15 microns in size, if these are allowed to accumulate in the engine oil and crankcase, you are drastically shortening the life of your engine. ANY defeat of any critical function of your PCV system is going to allow this, and/or worse. Allowing pressure to build and vent is also damaging over time to the rings, ringlands, and cylinder walls due to "ring flutter" and other damage caused by ring instability, so you want to pull vacuum/suction at all times, and NOT ever vent pressure as it must first build until it can vent, and no good comes from crankcase pressure.

So, the systems that deal with this properly are addressing the dirty, or foul side with a truly effective separation device, and w special separator that is used on the "clean, or fresh side" and add a secondary evacuation suction source for when the engine is under acceleration and no intake manifold vacuum is present.

I'll stop here for now and invite questions and discussion on the GDI engines in general, and more specific GM's and what they have done to reduce the ingestion, and why this affects EVERY single GDI engine made in the World from every auto maker. Understanding and making the correct emissions compliant, not effecting warranty changes to ensure you get the longest enjoyable life out of these awesome engines.

MikeLsx

Like Bigfoot. It's just a myth.

COSPEED

Sure seems some really go out of their way to convince others it is, yet not a one can show pictures and evidence of the contrary!

Really want to encourage ANY that doubt this to remove their intake manifold and take actual pictures and post here with their mileage at the time.

NoOne

Meth keeps the valves clean though, right?

COSPEED

If it was sprayed at all times yes, but then you take away the anti detonation effects of DI as you have a fuel present during the intake and compression stroke. When it does spray though is generally when someone is in full boost and that is when it does actually help.

What it does though is slow the rate of coking depending on how often your spraying it. I like to boost reference the controller to come on when needed, but I also use 100% Methanol and not a 50/50 mix. So yes, to a small extent it does. Good contribution!

MikeLsx

haha i was just playing.

COSPEED

I follow your posts, you are more "enlightened" than most!!! Brains and common sense.

sycraft

I was just playing too, but my post was deleted. lol
I do agree that you need to be aware of what your engine is doing, some may never need it, but others will definitely see a benefit

RussM05

What about intake valve cleaners such as the spray from CRC?

COSPEED

With a port injection, or better, a carbureted engine the carbon deposits these are good for are soft and only on the piston tops and combustion chamber. Over time these deposits have a negative effect on the quench area, etc. so they were beneficial on these older engines. The problem with any solvent based upper induction cleaner in use with GDI is these deposits are very hard and also large in comparison on the intake valves.

A port injection engine cannot build any deposits on the intake valves as the diagram early in this thread demonstrates. What happens when a solvent based cleaner is used, it soaks into the deposit causing it to expand and crack and up to 50% of those deposits will break loose and most is expelled out of the exhaust. Unlike the soft deposits of earlier fuel injection, these are many times the amount and it is impossible to not have some of the small hard particles forced between the piston and cylinder wall causing scouring (scratches and gouges) so that alone is a reason to never use other than say at less than 10k miles right after installing an air/oil separating system to clean some of what is starting to build. The real danger is if a chunk breaks loose large enough (like in the pictures in my first post) to become stuck between the valve and seat thus allowing the piston to make contact with the valve and bend it or cause even more damage to the piston as well. The valves must be able to move freely as they cycle so many times per minute into the guides, and any deposits on the stem are pulled into the guide each time it cycles wearing them prematurely. This is where using these solvents will not prevent this wear (tons f pictures to show this). So, the chance of real damage from breaking loose the deposits and the wear that happens constantly as long as these deposits (even light ones on the stem) are drawn in acting like sandpaper wearing the guide. The guide is generally a softer material than the valve to prevent galling, etc. (bronze allot is common) and the guide also maintains stability of the valves movement. When this wear occurs, the valves become unstable (higher RPM's most noticeable) and then do not contact the seat evenly every time they close stressing the tulip portion (see LS7 Intake valve failures for more info) and also allowing more oil ingestion via the guide (the valve seal on the upper side of the valve keeps just enough oil on the valve stems to lubricate, but not be an ingestion issue. These will wear/tear over time as the valve becomes unstable).

So, add the damage that can occur to the catalytic converter when the shock of the solvent and the large amount of hard debris hits the catalyst material, it is not recommended to be used with GDI, but is a good benefit to a port injection or a carbureted engine. In fact, Ford dealers have had notices sent out to NOT perform these on the GDI Ecoboost engines, but as it is so profit heavy most dealers ignore this. In addition to the issues and concerns laid out above, they also are seeing damaged hot side turbine blades as these larger chunks hit them at the high RPM's the blades turn at.

Excellent question. Solvents can be used w/out much concern on non-GDI engines, but as most can see, these companies (BG/Seafoam/CRC, etc.) are in a panic as their main use is causing damage to GDI engines, etc. and they have no other business model. That and no additive you put in the fuel tank now does anything, where fuel injector cleaners, etc. were and are a benefit to Port injection, it is throwing $ away with GDI as no fuel touches the valves and the injectors rarely clog at the high pressures they operate at now. They are all pushing hard to sell these as GDI solutions, but any tech tearing these down can attest, it is not worth the risk.

COSPEED

Here is a sample of worn valve guides, but with the LS7 and this is due to faulty machining/etc. as the LS7 is a port injection engine, this wear has nothing to do w/deposits or coking...but the results are similar:

"2007 Z06 23884 miles

I got it at 22890. Previous owner did not track the car.

Add me to the list
I am filing a complaint

1 Int .008"
#1 exh .006"
#3 int .0085"
#3 exh .005"
#5 int .0085"
#5 exh .010"
#7 int .009"
#7 exh .005"

#2 int .010"
#2 exh .011"
#4 int .010"
#4 exh .012"
#6 int .008"
#6 exh .017"
#8 int .007"
#8 exh .006"


Max GM spec is .0037" which would roughly be .0075" on the wiggle test. So basiclly if the wiggle test is over .0075" the guides are out of spec."

COSPEED

Anyone with a GDI engine (LT1 and LT4) step in and ask questions. Keep the discussion going.

glava2876

A couple of days ago I direct ordered the Elite Catch Can and Clean-air separator for my 2015 Z/51 w/1,300 miles and also my 2015 GMC Denali Crew cab 6.2 w/ 1,900 miles. I'm convinced that it is a great idea on the Corvette, but am not as sure on the GMC with the wet sump -what is your opinion?
For both, I figure is it cheap insurance VS the cost of the vehicles -however, though I don't mind spending money, I hate wasting money.

W88fixer

If this is such a horrific issue, I'd think we'd be seeing all sorts of massive engine issues from all the major auto makers, GM, Ford, Chrysler, Mercedes, Porsche, BMW etc. Doesn't seem to be happening.

I seem to recall that GM ran LT1 for 120K miles using the worst rot gut Chinese gas they could find and did it w/o issues.

Maybe people like to put out the sky is falling warnings? Don

MikeLsx

This is what i have been saying. I think in general DI engines are going to show more carbon build up, but I simply do not believe to the rate at which coSPEED2 says it is.

GM has mass amounts of DI engines on the road. wont be surprised if just about every engine they make is now DI. At 30-50k miles they are going to see MASS amounts of carbon build up(according to this thread). GM would have warranty claims like crazy if all the engines have major build up at 40k miles. Lets not forget GM also for years had the 100k mile warranty. According to coSPEED2 at 40k miles the valves are already toast. at 90k miles the car shouldn't be turning out. Yet they do.


Heres where i stand. I am waiting for high mileage LT1 and LT4 pictures to start rolling in. I also plan on checking my valves at 20k miles. If i see real data that supports coSPEED2 claims I will be a real believer.

Recently a Z06 LT4 owner posted at clean valve at 10k miles. a owner, not a vendor. its funny, vendors were pushing catch cans on the LS engines. Yet they are not DI.

EcoBrick Bob

3M makes an engine cleaning kit that you spray into the intake that will help remove these deposits.

However if the condition is really bad, the good news is you can get the intake manifold off in less than 1/2 hr to get a visual as well as access to clean with walnut shells.

Good idea to check on buildup between 20K & 30K miles.

COSPEED

ALL GM engines are now GDI for 2016 and up, all GM truck engines have been since 2014, so yes it does, and there are more trucks out there with pictures of their valves at 10-15k miles and they are horrible. Good move.

All except Mopar (Mopar has been the lone hold out and still uses port injection) have this as horrible issues, do a simple Google search on "GDI intake valve coking and see, and to help, here is a late model BMW with 20k miles on from BG's website showing how severe. EVERY forum for each of the manufacturers you listed have long threads with pictures, complaints, before and after cleanings, etc. So, you cannot find a single example where this is NOT severe with any you listed except of course Mopar who is not GDI.

Here are a few reads for you:


And videos from BMW techs:



Audi:


VW:

GM:

SO where have you been searching that is not showing you how widespread this all is? Not a single auto maker admits to this, so it is not front page, but in the automotive engineering side of the industry it is the #1 issue all are battling


All the actual pictures, industry data, tolerances on wear to the valve guides is all out there for you to see for yourself Bob......more than you could read or study in weeks. So what of all this shown my techs from virtually every auto maker in the World indicates any different? And the videos and pictures of the severity at 5-10 k miles on GM's V8's (much less all the millions of GM V6 and L4 GDI engines leads you to believe otherwise? Take this bet, how many miles on your car? I'll remove the intake manifold for free and you can inspect your valves up close and personal.

And for those that have not researched "intake valve coking on GDI engines,

click this link for a little eye opener:

https://www.google.com/search?q=GDI+...w=1600&bih=775

ANd Bob, there are a dozen or more companies selling solvent based upper induction cleaners, and they are fine for port injections soft carbon removal from piston tops, etc, but with GDI Ford states ANY use voids the warranty on a GDI vehicle due to the damage these hard abrasive deposits cause when they break loose and score cylinders and pistons, and the bent valves from larger chunks breaking loose and preventing the valve from closing and PTV contact occurs, and more.

I am not selling ANYTHING! I was hired to share my expertise and experience working in the industry as an Automotive Engineer for decades to educate as there is SO much mis-information out there when it comes to GDI and the unique issues that go with them.

Go to SAE.org and read the research papers on all of this. This is the most threatening issue today's automakers face today, and pretending it does not exist is the strategy to date....but the more that open up their engine and see, the more the word gets out.

Education, not mis-information is the ONLY way any that truly care will learn.

thrilled

Are you saying if I don't get A good quality catch can that maybe 50K miles I will probably need A valve job?

Wormwood

Okay... Okay!!! I'll take the hook on this one.

My C7 is my 2nd GDI engine, before all this I had an Excursion diesel, a person at Wal-mart out of the blue asked me if I was interested in selling my Excursion. Turns out he was REALLY serious & I made out really well. All except I was without a car. I had my heart set on a corvette but was a year too soon, so I looked around for the a cheap little sports car to tide me over until I could dealers started taking orders on the C7. I found a Hyundai Genesis Coupe that had a V6 GDi engine. This engine suffered from the same black tar crap on the valves as does the LT1. So I wound up ordering a Aquamist system but installed it in each runner (so 6 nozzles..) to get the max. cleaning effect. I had to order methonal mix by the case & additionally had to order straight methonal to increase my mix beyond 50/50 ratio. It got a little expensive but in the end it did finally keep the valves. I never really saw a increase in mileage due to it's use however I only ran it for about a year & then traded off.










Now with the LT1, I done 2 cleanings manually & a half cleaning with an intake system. Everyone has probably seen the pics. of the valves I cleaned, but here's the BG Products VIA or Vehicle Injection Apparatus. If you want to bring attention to yourself get one of these thing & a BG Products Direct Injection Cleaning Kit. The cleaning kit comes with 2 liquids one of which can be sprayed via the VIA (... hehe) into your intake. Fair warning though you will create a cloud of smoke so large the neighbor will think the city is on fire & that's within the first 5 minutes. I saw no improvement during the 5 minutes I used this BG setup nor could I imagine any city allowing this to take place anywhere. Search youtube for people trying these intake cleaning systems




Wormwood

MikeLsx

No he is saying at 20k miles you will need it. At 50k your car won't start.

And that goes for every DI engine. Lol