427 engine (part 2) - RHS block

[shakedown067]

Glad you enjoyed some time away!

[Rich Z]

Talked to Aaron today. He had good news, as well as the trypical bad news...

Good news is that the tune is finished and the car is running great. Well, mostly done, as Jim hasn't tweaked the tables for when the AC is running quite yet.

As for the bad news, it appears that there is too much pressure in the crankcase when boost hits max. Appears to be blowing oil out of the rear main seal. Aaron is looking into venting the pressure out of the valve covers through another catch can, and hoping that the rear main seal hasn't been damaged.

Man, talk about the "death of 1,000 cuts".....

[RevXtreme 1]

Only 2 things can cause that.

1. They have the crankcase evac system plumbed/routed incorrectly (probably trying to use the valley cover vent to evac a big cube FI build.....will never be able to. You must evac from the drivers side rear of the valve cover fitting.

2. You have piston/ring/cyinder damage allowing excess blow-by. Only way to determine this is with a leak-down test. NOT a compression test. A compression test will ony show serious internal issues.



Understanding the evolution of the LS series
crankcase ventilation system


I'll address GM's path to improving the oil ingestion issue, but the trade off is less effective crankcase evacuation. The goal of balancing proper evac with ever stricter EPA emission rules makes this a trade-off.

First with the introduction of the GenIII LS1 in 1997. The crankcase evac route was drawing it from both valve covers at the rear of each with the fresh make up air drawn from the top of a tube on the throttle body. This allowed a great deal of oil intrusion from both the valve covers & through reversion into the TB in front of the blade.

The next revision came with the LS6 and the valley cover. This helped some with the oil ingestion, but the trade-off was a far less effective crankcase evac as the drivers side valve train got virtually no flow through to flush & evac the harmful combustion byproducts, and the early valley covers allowed to much oil to be drawn out with the gasses. Enter the LS2 and a redesigned valley cover with a baffle system. This worked quite well and minor changes to the newer releases helped as well. Leaving us with the same issue of the drivers side valvetrain not being flushed properly, but the 90mm TB had the fresh air tube eliminated and the make-up air drawn from the intake air bridge. This still allows some ingestion at WOT when the intake manifold vacuum is at its lowest. The L99 then went to drawing from rear of the drivers side valve cover and a still further improved baffle in the valve cover. This solution at least allows proper flushing on both banks and the crankcase itself. Picture the fresh air entering the front of the passenger side valve cover, flowing around the rocker arms, down the pushrod valley, through the crankcase, up the drivers side pushrod valley, around the rocker arms, and exiting the rear of the drivers side valve cover and pulling (flushing) the harmful combustion byproducts out. The problem is the flow is limited and the evacuation still inadequate. When allowed to flow at an effective rate the oil ingestion rises and the problems caused (listed in the earlier posts) are still an issue.

Also, the LS3 STILL pulls from the valley cover which is not all bad except the fixed orifice is to restrictive to allow proper flow.


The 2 different FI models of RX oil separator

You have 2 styles of FI can. The top mount super chargers (Maggie, KB, Whipple, E-Force) directly pressurize the cylinder head runners so no intake manifold. This requires only 1 check valve as your only dealing with the crankcase evac and the excess pressure in the crankcase. The RX can will evac at all operation levels using the vacuum provided by the top mount head unit itself and will prevent any back-flow or reversion.
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For the turbo or front mount super charger you have a completely different set of challenges to overcome and the RX dual valve unit is the ONLY oil separating can on the market to address this. The turbo/SC pressurizes the OEM or aftermarket intake manifold when building boost and besides the additional blow-by resulting in excess crankcase pressure, you also have any connection to the intake manifold allowing the boost to leak into the crankcase causing even more issues. When your at idle or non-boost cruising the intake manifold is not positive pressurized and acts as a NA application providing the vacuum needed to evac the crankcase. But when in boost, the intake manifold is pressurized and there is no vacuum source. The kit manufacturers of these (STS, ProCharger, Vortech, etc.) just send a check valve to close when under boost, but this prevents any effective crankcase evac and not only is there the pressure to deal with, but the harmful combustion byproducts are left in the crankcase where they cause damage over time.
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The RX can uses the intake manifold vacuum for evac during non-boost operation, and when boost is detected it closes the valve to the intake manifold and the second valve opens using the inlet side of the head unit (turbo/SC) for a vacuum source so no matter what the level of operation the crankcase is evacuated and excess pressure is dealt with. When you let off the gas and fall back into non-boost operation the valves open & close in just the opposite ensuring no oil into the intake system AND proper crankcase evacuation at all times.
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The problems with the solution the FI manufacturers include is it is only effective at part of your operating and results in excess crankcase pressure carrying oil vapor/mist into the intake air charge when in boost so you experience detonation and the rest of the issues related to oil ingestion.

[Rich Z]

Thanks for the explanation, Tracy. Sorry I didn't reply earlier, but I didn't even notice you reply until just now. Quite frankly, I'm just getting tired of hearing myself talk about this car. In another week, this will be ongoing for an entire 2 years, so I guess I'm finally getting numb about the whole thing. I no longer feel that I even own the car, so what the hell does it matter at this point?

Anyway, I went out to Aaron's yesterday (Friday). He just got in a rather robust looking catch can with HUGE inlets and out outlet air filter. He had fittings welded to match on both of the valve covers. Just needs to get that all hooked up.

From what I recall, yes, he said the original catch cans I have are plumbed to the valley cover, and only using 1/4 inch plumbing.

Aaron said he would call me yesterday to let me know when Jim was showing up. He thought either Friday or Monday. But I didn't hear back from him.

He told me there is still a problem in the tuning whereby the engine wants to stall until it gets warmed up. He also needs to charge up the AC compressor as different tables are being used when the AC is running that need to be looked at.

[RevXtreme 1]

That setup will not evacuate the damaging combustion byproducts out of the crankcase, it will only release excess crankcase pressure. Now if you change oil after everytime you run it you should be fine, but you do NOT want the water, unburnt fuel, abrasive carbon particles, sulfuric acid, etc. in your crankcase damaging parts and contaminating the oil every cool down. The solution he has come up with is band-aid at best. Now if he uses it (sounds like a Moroso vacuum pump catchcan) with a belt driven vacuum pump your fine....but I doubt he is. Sounds like the average tech that does not understand proper crankcase evacuation.

Here is the read:

Understanding PCV Systems


To understand why we need a proper PCV system one must understand what takes place in the crankcase during the average day of driving. First off, all internal combustion engines have a certain amount of "blow-by" or leakage past the piston rings into the crankcase. This consists of several compounds such as unburnt fuel and a small amount of the combustion gasses that result from the explosion of the air/fuel mixture. The combustion gasses contain several nasty things including sulfuric acid, carbon particles, and other caustic compounds that will contaminate the oil over time. In the crankcase there is also a certain amount of water, or moisture from condensation. Even if never run, an engine will accumulate moisture from the heat of the day to the coolness of the evening depending on how humid the climate is where the motor lives. Every time the motor gets run up to operating temperature these compounds are "gassed off" and with the OEM system it all gets "flushed" or pulled into the intake manifold where it is mixed with the intake air charge and burned in the combustion process and further in the catalytic converter before it is exhausted into the air as mostly just water vapor at that time. Now of course, a small amount keeps leaking past the rings into the crankcase and completes the cycle all over again, but without a proper vacuum pulled ventilation system....these nasty compounds will break down the oil and reduce its protection properties and the corrosive aspects start to rust internal parts resulting in reduced engine life.
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In the "old days" of our grandfathers, the engineers that designed engines new the importance of evacuating these nasty compounds and the design was extremely simple. First was nothing more than plain breathers to allow excess crankcase pressure to be released or vented. But the damage from not "flushing" all the gasses out resulted in very short engine life (of course the oils of that day were nothing like the protection today's synthetics provide) so the next change added a vent tube, or evacuation tube that ran from the top of the crankcase to low on the car where the air streaming past would create a suction, or vacuum that would pull the vapors out and vent them directly into the air with a breather (barely filtered with a wire mesh type media that was oiled to catch dust & dirt) allowing the "fresh" makeup air in to complete the flushing process. Now this resulted in greatly increased engine life, but as the motors got worn oil would start to drip out the tube and drip onto the roadways, then the rain would wash it into the ditches, where it would enter the ground water (you know the rest of the EPA story) and the gasses just vented to the air.
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As the EPA and the powers that be mandated stricter emission laws the system was refined more and more ultimately evolving into what we have today. A completely sealed system that uses the vacuum provided by the intake manifold to draw these vapors out, and the filtered fresh makeup air is drawn from the main air intake system and filtered by the main air filter. This results in very clean emissions, but the unintended issues are the detonation or "knock" that occurs when oil is introduced into the combustion chamber that the knock sensors pick up (before we*can hear it)*and pull timing to protect the engine from damage, and thus reduced power. Another result is the carbon buildup on the valves & piston tops (any techs reading this can surely verify the amount) also resulting in decreased performance and less power made.
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The purpose of a proper oil separating catch can is to route these gasses through a baffle system that provides the most contact possible with the outer surface resulting in the oil being trapped and removed from the other gasses that do continue on through the intake and are burnt and consumed. It does NOTHING else in ANY way to the engine oil itself....it can't.
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Deleting your PCV system:

While this will insure NO oil the the intake tract via the PCV, it will greatly shorten the life of your engine if street driven. The worst example I have seen is to cap off all the fittings and run an open hose from each valve cover to near the ground. One would think “they are both releasing pressure, so what can it hurt”. The answer is plenty. Lets take the basic principle of the Venturi effect. Whip a piece of hose around in a circle so that air rushes past the end. This will result in suction from the end of the hose near the center of the radius. Now with a car traveling down the road at speed, both hose will have air traveling past the ends and one ultimately will have more air rushing past thus creating more suction, and the other will them become a vacuum tube sucking up dust, dirt, water, sand, etc. directly into the engine from the side with the least suction. Depending on the amount of dust & dirt on the roads you travel (just look under your hood to see all the sand & dust that accumulates on the engine exterior). So it may take years to destroy your engine this way, or it may take no time at all. To see this if you have been misguided into doing this just remove each valve cover, and looking up into the baffle in each you will see the accumulated dirt built up as it comes in contact with the oil.

Now, addressing the "Home Depot" oil separator, it will and does catch a small amount of the oil but the majority still gets past into the intake (we used these and then the other cans that popped up on the market through the years before designing the ultimate final product that is offered today) and the reasons are simple:
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It is plastic and transfers heat very inefficiently so very little condensing takes place.
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The size. Anything less than 1 qt capacity and there is not enough surface area to be as functional, and the volume needs to be enough to allow the flow to slow enough for the oil to drop out of suspension.
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And the lack of an effective baffle system allow oil to be pulled directly through.
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As for having steel wool or another type of filter media inside, this will work well at first to trap oil....but as soon as it gets saturated droplets are pulled off and into the intake.
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Why don't the auto manufacturers incorporate something similar? Cost and the added maintenance was deemed something that would NOT be accepted by the general market. (even though it is as simple as draining the can at each oil change).
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Bottom line is this: The OEM system does a great job of meeting emission standards and removing the harmful contaminants, but the unintended consequences are the oil that is drawn into the intake charge. For an engine to produce the maximum amount of energy per explosion (of the A/F in the combustion chamber) you want air & fuel only....any amount of oil in this mix will hamper the explosion resulting in less energy released, detonation, and carbon buildup. Trapping and removing this oil before it gets into the combustion chamber is the ONLY solution to maintaining the maximum efficiency and prevent excess carbon buildup.
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[Rich Z]

Beats the heck out of me.... At this point I think the best thing to do is to just get the car running and trade it in even up for one of those "smart cars". Obviously what I did to this Corvette certainly wasn't smart, so maybe I can make up for it with one that is labelled as being "smart"....

[Rich Z]

This just keeps getting better and better.

Talked to Aaron today. From the sound of his voice, I knew I was in for some bad news. I actually thought it would be worse than it turned out to be. I'm fully expecting that engine to just blow, and from the way he started telling me what happened, that was what it sounded like.

But no, no throw rod or anything major catastrophic. Just a Jesel rocker arm shaft broken on cylinder #7. Not that this is something that is run of the mill in a build, I suppose. But still, what the frickin' else can break?

Aaron talked to Jesel and they thought perhaps the bolts holding the shaft in place hadn't been machined deep enough or something to that effect.

This is all just stupid ridiculous. I asked Aaron that before he gives up on this turd to just please make sure it is driveable and in presentable enough shape that I can at least drive it to a car dealer to sell it or trade it in. Maybe I really should do that before the engine does finally blow.

Seriously, how many people reading this fiasco think I really don't even have a blue C5Z and am just making this crap up? I couldn't have sat down and written a story that would have been as "worst case" as this is....

[RevXtreme 1]

It is still a beautifull car Rich.....one of the nicest C5 Z06's around IMHO.

The rocker issue does not sound right if the valvetrain geomitry was set up correctly. We use Jessels & T&D as standard on our drag builds and have over .800 lift cams in these builds and have never had an issue in over 15 years since using them....they are the best bar none, and with the smaller lift cam you have I suspect there is a deeper issue.

As I have offered before, I am always available to diagnose and do it correctly (in a short amount of time.....we put out 700-800-1000+ hp builds every month or two w/out issue in tune or engine/drivetrain) so to just make it run and trade it at this point you will loose far to much since the car has above average value if just done correctly.

I know we have said "have faith" too many times in the past, but to build it from scratch should only take a few months start to finish. There is no excuse for it to drag on and constantly have new issues popping up like this.

You know where to reach me.

[Benjamin]

Originally Posted by RevXtreme 1

Sounds like the average tech that does not understand proper crankcase evacuation.

Aaron is FAR from that. he has built MANY boosted cars, and they are running and driving on the road still today.

remember that the motor will never be ran 100% of the time on boost. therefore the natural vacuum from the intake will evacuate the super duper bad stuff that can harm the motor only if the oil isn't changed but every 10K+ miles.

if this was a drag race or road race only car then the kit you have would be a must but on a car that cruising should be in and out of boost allowing the natural vacuum to evacuate the crankcase is perfectly acceptable IMHO. I am an average tech and have built MANY boosted motors to understand proper crankcase evacuation.


Rich, I hope you get the car back soon and can enjoy it before you sell it or make it a trailer queen and get a 1-ton and an enclosed trailer to take it to different shows throughout the US. With all the documentation you have you can have one heck of a display on why to keep a car stock........

[Rich Z]

I guess I'm just numb from the whole thing by now. Tomorrow will mark two years since I drove the car into Chris Harwood's shop.

As for the car becoming a trailer queen, I doubt that. A lawn ornament with the roof cut off to make it into a BIG planter, well maybe..... A monument to one of the dumbest things I have ever done in my life.