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I'm pretty sure they said the same thing about the LT1 when the Stingray was introduced.
They did*.

"PCV-integrated rocker covers: One of the most distinctive features of the new engine is its domed rocker covers, which house the, patent-pending, integrated positive crankcase ventilation (PCV) system that enhances oil economy and oil life, while reducing oil consumption and contributing to low emissions. The rocker covers also hold the direct-mount ignition coils for the coil-near-plug ignition system. Between the individual coil packs, the domed sections of the covers contain baffles that separate oil and air from the crankcase gases — about three times the oil/air separation capability of previous engines." All-New 2014 Corvette LT1 V-8 a Technological Powerhouse
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*Just doin' my part to get this thread to page 41... :)
 
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How can we ask TJ
Already done on the other forum. But do you think anyone at GM is going to admit there's a real problem?
 
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It's worth revisiting the causes of carbon build-up on intake valves. There are three primary mechanisms involved, listed in no particular order:

"- Intake valve deposits form as a result of oil slowly seeping past the intake valve guide seals and down the valve guides. A tiny amount of oil is necessary to lubricate the guides, but when oil reaches the hot surface of the valve, it can stick and burn forming heavy black carbon deposits that gradually build up over time. The higher the mileage on the engine and the greater the wear in the valve guides and seals, the faster the accumulation of black carbon deposits on the intake valves. Low viscosity motor oils (such as 5W-20 and 0W-20) may make the problem worse because they are thinner (to reduce friction) and flow more easily down the valve guides. Conventional motor oils also have a lower flash point than synthetic oils, which can also increase the formation of deposits over time.

- Another contributing factor to the formation of intake valve deposits is unburned fuel vapors and oil vapors being siphoned back into the intake manifold through the Positive Crankcase Ventilation (PCV) system. This is done to control crankcase emissions and to remove moisture from the oil (which helps prolong oil life). The fuel vapors, carbon particles and oil droplets that the PCV system routes back into the intake manifold are reburned in the engine to reduce pollution. But these same vapors can also form carbon and varnish deposits on the intake valves (the more blowby an engine has due to cylinder and piston ring wear, the greater the volume of crankcase vapors that are pulled back into the engine by the PCV system. High mileage engines typically have more blowby than low mileage engines, so the build up of intake valve deposits is usually faster)
." Intake Valve Deposits in Gasoline Direct Injection Engines

- "Third, the intake valve goes into the combustion chamber, regardless of whether it is port fuel injected or direct injected. When it does, for that small period of time, the valve is exposed to combustion byproducts that can stick to its neck. If the previous combustion cycle was less than optimal, the intake valve is exposed (unlike the exhaust valve, the gases passing by are not hot enough to burn them off)." Solving Carbon Deposits In Direct Fuel Injection Engines

Also:

"If you look up direct injection carbon deposit problems on the Internet, engines from BMW, Audi and VW always rank the highest. Engines from GM and Ford that have been on the road for at least four years hardly have a carbon deposit complaint.* What’s the deal?
Some direct injection engines have bad timing. The modern engine typically has variable valve timing and even cylinder deactivation. The engine management system can control when, how long and, in some cases, how deep the valve goes into the combustion chamber. If an intake valve is dropping into a combustion chamber with combustion byproducts or unburned fuel, the valve might be exposed to the precursors that cause carbon build-up." Why Direct Injection Engines Develop Carbon Deposits
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So, the question remains, how to minimize buildup on the intake valves with direct injection? Here are what the "experts" say:

- Use high quality fuels that lead to efficient combustion and minimal combustion products - "Some carmakers, including BMW and Kia, have issued technical service bulletins (TSBs) to their dealers recommending that drivers use only name-brand detergent gasoline–without ethanol additives–and that they periodically add a fuel-system cleaner when they refuel. (A TSB is an alert that the automaker sends to dealers to warn about ongoing problems with individual models and how to fix them. It may allow dealers to make repairs at little or no cost to the customer as a goodwill gesture.) It’s important to note that not all cars with direct injection experience long-term problems." Pros and Cons of Direct Injection Engines - Consumer Reports Note that adding a fuel system cleaner may primarily insure that the injectors stay clean, maintain their proper spray pattern, and minimize combustion products that could coat the valves.

- Use a high quality, full synthetic motor oil and change it frequently to minimize coking from valve guide seepage, combustion products and PCV aerosol oil. Personally, I use a full synthetic with an oil change interval of 5,000 miles. This often leaves about 30-40% oil life remaining (based on the car's oil life monitor), and I prefer this scenario.
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"How fast the intake valves get dirty does not seem to be a function of fuel quality or how much ethanol alcohol is in the gasoline. Rather, it appears to be influenced most by how often the engine oil is changed. Oil vapors and combustion byproducts that are drawn back into the intake manifold through the PCV system seem to contribute most to carbon deposits on the intake valves.

My advice is to change your oil every 3000 miles if you only do short trip stop-and-go city driving, or change your oil every 5000 miles if you do mostly highway driving. If you want to minimize carbon buildup on the intake valves, don't push your oil change intervals to 7500 miles or longer unless you are using a high quality full synthetic oil (which usually has less volatility than conventional motor oil).

Changing your oil regularly will help minimize the carbon buildup on the valves, but eventually they may still get dirty. If that happens, it may be necessary to clean the valves every 25,000 to 30,000 miles with an aerosol cleaner that is sprayed into the intake manifold
." Intake Valve Deposits in Gasoline Direct Injection Engines Note the differing opinion on the influence of fuel quality from this author. Cleaning with a product like SeaFoam every 25,000 - 30,000 miles is a common recommendation to remove any intake valve build-up.
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" - But the number one method for preventing a carbon buildup problem is updating the engine management software. New software can reduce carbon deposits by reducing the exposure of the valves to conditions that cause carbon buildup by adjusting valve and spark timing." Solving Carbon Deposits In Direct Fuel Injection Engines - This is a very interesting point, but I suspect GM has already optimized the engine management software with these factors in mind. I expect that this opinion is more relevant for older DI engines.
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Q.E.D.
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*Andrew Markel is the editor of Brake & Front End and Servicio Automotriz magazines. He has been with Babcox Media for more than 12 years. He is a technician and former service writer and holds several automotive certifications from ASE and aftermarket manufacturers. He can be reached at [email protected].
 

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It's worth revisiting the causes of carbon build-up on intake valves. There are three primary mechanisms involved, listed in no particular order:


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Q.E.D.
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*Andrew Markel is the editor of Brake & Front End and Servicio Automotriz magazines. He has been with Babcox Media for more than 12 years. He is a technician and former service writer and holds several automotive certifications from ASE and aftermarket manufacturers. He can be reached at [email protected].
Good review and no reason to panic -you site some good references. However when I see Consumer's Report, for example, I question their understanding of performance cars!
There is a difference in potential "coking" problems with a normal small displacement engine, driven as a "grocer getter" car and a high performance engine with large diameter valves driven as it should be! The later has intake valves that get much hotter. That is why they are often made of higher temp materials. Folks like Ferrari and Porsche are expressing some concerns. Toyota even has at least one engine that uses direct inject with added port injection that is occasionally activated! That allows gasoline to periodically wash past the intake valves.
Perhaps the most compelling reason for me to use a catch can is this published article:
An article in the December 2014 issue of Hot Rod magazine quotes a GM engineer (John Rydzweski, Assistant Chief Engineer for Small Block V 8’s) discussing the LT4 had some general comments about “coking” issues with DI engines.
This is not just any GM Spokesman who says “Don’t worry everything will be OK!” This is the GM Assistant Chief Engineer for Small Block V8’s!
Here is a quote:
“A little bit of oil on a port-injection engine can help lubricate valves, but because the Gen 5 V8’s (all C7’s as the LT1) are Direct Injected, there’s no fuel washing the back of the intake valve. That means oil in the PCV system can end up sticking to the back of the hot intake valves impeding airflow and eventually preventing the valves from seating properly.”

I thought Tadge Juechter did a good job of discussing the issue in his Forum response. However I did not come away with believing all was well. More like "many cars can stand some build-up on the valves!" Having spent time with polished intakes, tuliped bright shinny valves in engines built for performance, "some coking" did not make me feel warm and fussy! Guess if you never put the “pedal to the metal” and don't exceed 4000 rpm it may not be an issue!
To each his own but I bought my C7 for performance and want it to stay that way. Not sure how much a “catch can” helps, but for the small investment it can't hurt! That published statement from the Chief Assistant for Small Block V8's carries more weight than the no doubt legal/marketing reviewed statement from Juechter, IMO!
I would think those trying to make a decision to use a catch can or not should read the available references and decide for themselves.
 

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Good review and no reason to panic -you site some good references... Not sure how much a “catch can” helps, but for the small investment it can't hurt!
Thanks Jerry, and for the same reasons you've mentioned I also use a catch can.

My interest is simply to get as much info (that we have access to) on the table as possible, so that we can all understand the situation.

With regards to the catch can, I drain mine every 1,000 miles (a convenient interval and easy to remember), and there is typically around an ounce of oil after that number of miles.

I prefer frequent drain intervals to keep the can's fluid level low, since the more oil you leave in the can the more opportunity it has to "slosh" up to the can's exit port, leading to a greater likelihood that the engine will get a "gulp" of pure liquid on a hard bump or other high-g event.

If catch cans aren't maintained properly, I suspect they may potentially do more damage to the engine than without one.
 

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Thanks Jerry, and for the same reasons you've mentioned I also use a catch can.

My interest is simply to get as much info (that we have access to) on the table as possible, so that we can all understand the situation.

With regards to the catch can, I drain mine every 1,000 miles (a convenient interval and easy to remember), and there is typically around an ounce of oil after that number of miles.

I prefer frequent drain intervals to keep the can's fluid level low, since the more oil you leave in the can the more opportunity it has to "slosh" up to the can's exit port, leading to a greater likelihood that the engine will get a "gulp" of pure liquid on a hard bump or other high-g event.

If catch cans aren't maintained properly, I suspect they may potentially do more damage to the engine than without one.
Agree. I do about the same. Pretty easy to check. However doubt many check their oil level per GM recommendations so doubt if GM installed one they would be checked and drain often and properly!
In fact with a dry sump the procedure for checking the oil level is enough different than a wet sump, some may not do it properly. I recall one poster saying, "I'm not going to use a watch when I check my oil!" If you want a correct reading you need to! On that subject, for fun I checked my oil level before I started the car after it sat for a week. There was no oil showing on the dip stick, probably 5 + quarts low in the dry sump tank, it all drained back to the pan past the scavenge pump gears! That's why GM says check hot oil after 5 but before 10 minutes. For those wondering, I checked it per the manual after I can back from a drive and the level was right where I left it at my last change, 1/2 way in the hatched area, about 1/2 quart below the max fill level.
 

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Sorry but I dont feel like sifting through 600+ posts to answer this question... Will installing a catch can void my warranty?
 

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Sorry but I dont feel like sifting through 600+ posts to answer this question... Will installing a catch can void my warranty?
Simple answer is probably not but it isn't out of the realm of possibilities; it is a modification to both the engine and the SMOG components. If down the road something happens to your engine while under warranty and inspection shows either the can was improperly installed or somehow created an issue regarding pressures it could result in at least a battle to get repairs under the GM warranty.
 
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Mine's been in the shop twice, with the tech under the hood both times, and the dealer hasn't commented on my can.
 

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Mine's been in the shop twice, with the tech under the hood both times, and the dealer hasn't commented on my can.
And my dealer's service department has no problems in general catch-can installs either.

However, and this remains the unanswered question, will they look the other way IF your motor blows up? The cost to replace an LT1 motor is $17,000, and the cost to replace a LT4 motor is $30,000. And starting a year ago, GM is now requiring dealerships to conduct two different tests in all major warranty claims AND also having a regional warranty approval specialist review those test results prior to approving a major claim. Will this change things, as dealers who like their special customers can not longer always go wink-wink (because you have been a repeat good customer of our dealership, we are going to look the other way on your engine tune, or your supercharger install, or you XXXX mod, etc.).

I say this is the unanswered question becuase, so far, GM has been approving engine replacement or repairs under some warranty-compliance iffy circumstances for new and low mileage C7's, and has also approved some by-backs on problem Corvettes.

However, will this happen in 2019 to an owner of a four year old Corvette with 42,000 miles, whose motor blew up on the track yesterday and had a catch can? Heck if I know...
 

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I still have the original hose. If I need to take my car in for a major engine repair, hopefully I'll be able to remove the can and return it to stock first. Of course, if the dealer has noted somewhere that there's a catch can installed, and tells GM, then I have a problem, although I can always say "prove it."
 

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we are using the dual valve can with integrated flow controlling check valves mounted inline and the RX cleanside separator at the oil sump
Thanx for the thread on this. I've been researching this issue and this thread has many answers, so thanx for your time!

Do you have a source to recommend for high quality inline check valves?
 

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I am using the Elite dual valve can. Check valves are built into the fittings that the hoses connect to.
 

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I think mine is just catch can only. Maybe I should have gotten the high end kit.

Is there a way to buy separately inline check valves somewhere?
 
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