catch can related info

Discussion in 'general muscle car related info' started by grumpyvette, Mar 8, 2011.

  1. grumpyvette

    grumpyvette Administrator Staff Member

    In every engine a small amount of pressurized gases from combustion pressure, during the engines power stroke that's been generated is getting past the rings, as the compression and combustion stroke begins before that cylinder pressure forces the rings out against the cylinder walls.
    and it is more than likely the cause of most oil leaks,internal pressure that builds in the in crank case in a slight positive pressure, results in your gaskets even if they were properly installed, being constantly subjected to oil trying too push past or through the seal, and having a good valve cover breather is one way to reduce the pressure build-up ,it the most common quick fix as it prevents pressure build up, but that constant oil flow exiting the breather carries with it, a constant fine oil mist.
    all engines have some pressure get past the rings but most have a breather that allows most of the crank case pressure to remain low, and a PVC valve that constantly allows the crankcase vapors to be sucked into the intake to be burnt, if your system works correctly the breather allows more air flow in than it ever does under normal operational conditions than it does ,crank case pressure out, as the PVC tends to minimize positive crank case pressures.
    If your carburetor or efi plenum intake doesn,t have a fitting for a PVC valve fitting and you have the hood clearance, its a good deal easier to drill and tap a 2" aluminum carb spacer for a vacuum connection, and that routes less likely to cause mixture distribution issues.
    A catch can, is a device that is designed to separate the droplets of oil from the air flow, condense it and route it either back into the engines sump or to be drained occasionally
    bores must be honed with a deck torque plate to simulate the stress of a installed cylinder head stress , the torqued bolts exert on the bore walls, the torque plate induces and duplicates that stress so that the bore walls will be pulled into the same relationship when you hone the walls concentric, rings won,t seal correctly in a non concentric bore
    [​IMG] ... 91201.html
    BTW we found we could just insert one or two stainless steel scrub pads in side the valve cover breather tube space, (A and B) as that will absolutely control any air flow turbulence, that tends to drag oil out the breathers and make the engine a oil soaked mess, oil mist collects on the maze of internal metallic surfaces then gravity tends to let the heavier liquid drain back into the valve covers.
    I know we did that on road race cars, for oil control on crank case breathers, and it drastically improved the flow back rates and controlled the formation of oil foam, allowing the oil to flow back with a noticeable reduction in air trapped in the oil.
    these links may help


    these electrical box punch tools work great for punching breather holes in some valve covers for rubber grommets, to mount breathers or holes in certain types of oil pan baffles etc.
    almost any cam will cause intake manifold reversion or pulsed low speed air flow in the engines intake runners , this often results in the PCV valve rapidly oscillating in response to the changes in air vacuum/pressure


    related threads




    Oil Catch Can is designed to effectively separate oil from the crankcase vapors, thereby eliminating all negative effects of excessive intake system oil contamination.


    The PCV (Positive Crankcase Ventilation) system is designed to regulate and remove fumes from the engine crankcase, and to alleviate crankcase pressure which
    could cause oil leaks or seal damage. The PCV system routes crankcase fumes into the intake manifold where they can be burned to eliminate harmful emissions into the atmosphere. The PCV valve controls the amount of crankcase flow volume depending on the engine's load. With large throttle openings (high engine loads),
    the more blow-by gases are produced, and the more the PCV system flows oil vapor in to the intake manifold. The PCV valve also functions as a check valve to prevent intake manifold flow from reversing back into the crankcase when there is a backfire, or during periods of high manifold pressure (boost) during forced induction by turbocharger or supercharger.
    Negative Effects of your Stock PCV System:
    Many owners with LSX engines can testify to the amount of oil residue that can accumulate inside the intake manifold,
    throttle body, intake track and even the air filter during aggressive driving conditions.
    There are various negative effects when excess oil vapor contaminates the intake
    system from the stock PCV system - such as:

    *Throttle body and/or MAFS (Mass Air Flow Sensor) malfunction or failure.

    *Air filter, intercooler (if equipped) and intake ducting contamination if oil pools and run back out the intake system after engine shutdown.

    *Reduced octane of the air/fuel mixture, which can cause detonation and the ECM (Engine Control Module) to retard timing, thereby reducing engine power.

    *Excessive carbon build-up on valves, piston crowns, combustion chambers and spark plugs. This also increases the chance of detonation and power loss.

    *Increased emissions & possible contamination of catalytic converters and oxygen sensors.
    this is just common steel wool with a detergent coating that will HURT your engine, as both the detergent destroys oils ability to lubricate and fine metallic trash in your engine will destroy bearings


    what you want is a stainless steel scrub pad, and place these only where oil vapor will collect and drip back into the engine like inside the breather cross over



    read thru the links


    viewtopic.php?f=52&t=2005&p=5328&hilit=breather#p5328 ... %20102.pdf
    Last edited by a moderator: Oct 25, 2017
  2. grumpyvette

    grumpyvette Administrator Staff Member


    Understanding the need for
    a proper PCV oil separating catch-can

    Any engine driven hard will ingest a certain amount of oil into the intake air system resulting in loss of power, detonation, and long term carbon buildup on the pistons & valves reducing the velocity and flow through the engine.

    Preventing this on a street driven car subject to emissions requires some simple modifications to the closed OEM PCV system.

    On all out race applications where emission rules do not apply, this is accomplished in different ways, but proper crankcase ventilation is a must! The crankcase gets filled with harmful combustion byproducts that if not evacuated will cause internal damage to your engine and shorten the usable life. These byproducts include: Sulfuric acids, abrasive carbon particles, unburnt fuel, water, and more. If you do not have a proper crankcase evacuation system these compounds will condense inside the engine and mix with the oil as well as begin corroding internal parts. It is NOT enough to just vent the crankcase pressure through a breather, but it must be flushed with a filtered fresh air source to carry these out & away. In an OEM system, these are burnt in the combustion chamber & further in the catalytic converters.

    In an off-road or race application, the engine is normally not used to burn them off.
    At the very least drag only motors have a scavenge evac system in the header collectors to pull vac, and anyone that's serious has a belt driven vac pump.....especially the Alky motors due to the amount of moisture the alcohol introduces to the crankcase.

    Want to see whats in your oil? A simple oil analysis will show you how much harmful stuff ends up in it.

    The oil analysis will show the acid build up....and no, it takes a year or two before you would see any substantial damage to your internal engine parts.....but an easy way is after 6 months or so of running like you describe pull a valve cover and look and the corrosion from the vapors on your rocker arms. This is the first place it is visible.

    Bottom line is, w/out a proper evac system you WILL sustain long term engine damage. It may take a few years to notice, but I build motors 6 days a week when not racing and see the results first hand.

    There are several other ways for oil mist to enter the intake manifold, the PCV system is the most common with the fresh air make up source (the fitting on the top rear of your throttle body) being the second most common. To eliminate that you need to cap the TB fitting and run a valve cover breather (installed as far from the crankcase vent as possible...ideally you want to pull filtered fresh air in one valve cover & evac it out the other or the LS6/LS2 style valley cover is second best) Then if it is excess crankcase pressure pushing oil vapor/mist out faster than the PCV can evac it you will see it pushed back through the line from the pass valve cover front to the TB and it is ingested from there. The 3rd point of ingestion is from reversion. This of course needs at least one piston/ring/bore/valveguide or seal issue that is allowing oil to be pulled into that one or more intake port and at high RPM's the reversion pulse will "push" that oil throughout the entire intake manifold. It will appear to have entered from the vac fitting that the PCV system uses but is really from one of the cylinders (reversion is a whole different process that is not widely understood but do a Google search and you can actually find some super high speed video of engines on dyno's where at high RPM's...9-10-12K plus the reversion cloud of A/F mixture is actually rising out of the intake runners or carb on a non fuel injected motor). To test for that just place a clean clear fuel filter inline between the catch can outlet and the vac fitting. If it gets oil on the can side, oil is coming through the can. If it first appears on the intake vacuum side, then it is reversion so you have a deeper issue.

    Having engine smoke or excess crankcase pressure? There may be a deeper issue. On the LS motors we pull apart it is usually # 7 ringland broken between the compression & middle ring, or the land itself broke off at the top. We also find the top ringland pinched or crushed down on the top ring (comp. ring) and metal transfer along the piston side has caused the oil & scraper ring to stick allowing oil & blow-by. Also, try this: at idle (vac is at it's greatest when at idle or when the throttle blade closes from high RPM's) remove the oil fill cap and hold your hand over it. Does it pull a slight suction? If so, all is good with most of the system and I doubt you have a damaged piston/ring/bore. But if there is ANY pressure pushing back you have a deeper issue and that is the cause of the oil problem.

    Now on big cam/stroker builds a can inline on the dirty side, and a can inline from the fresh air source may be needed (the bigger the bore & longer the stroke, the more crankcase pressure is built up) If it is forced induction, then you have a whole new process to deal with......and that is the PCV system works properly when at idle & non-boost, but when you start making boost you have switched from the intake manifold being negative atmosphere to a pressurized component and the PCV system is rendered useless and pressure escapes wherever it can. The solution then is to have one way check valves inline so the vacuum need for proper evacuation comes from in front of the compressor (head unit) through a line run to the air filter.

    This is getting a bit long and I hope all can follow this, but if not ask me specific questions for clarification so this helps all. I'll go over every type of solution and the pros & cons of each....and remember, this problem is NOT just in the GM LS based engines, but is an issue with ALL modern closed systems. We just tear into our cars where as the Mercedes or Lincoln owner never even realizes there is an issue.

    I also wanted to address the water in the oil. You will NOT fill your crankcase up in short order with just breathers. What happens is each time your engine reaches operating temp the unburnt fuel, water vapor, combustion by-products will gas or "flash-off" as vapor. But only the excess crankcase pressure being relieved through the breather will carry any of that out....and without a proper evac system, a good amount remains in the crankcase and re-condenses back to droplets that coat the internal engine parts as your motor cools down and it contaminates the oil. Every time you heat cycle you are adding more contamination and it is not very visible to just "look" at your need a professional analysis to see just what is accumulating in your oil and how it is breaking down its ability to protect...but the corrosion from the sulfuric acid is also very damaging over time (I'll try to post up some pics of parts showing just this in the near future). Just pull the dipstick on a diesel 20 miles after an oil already "looks" black & dirty, but is still new and providing the proper protection. Sight is deceiving. Oil might look pretty clean or dirty but an analysis report will show destructive levels of contaminants.

    And finally, some have gone so far as to cap off the entire system and run an open hose from each valve cover to near the ground. While this will eliminate all oil getting into the intake via the PCV system, the damage done by the hose with the least amount of air moving past it while at speed will suck dirt/sand/dust/water/and who knows what else directly into the motor via that valve cover. It may take some time (depending on how clean the roads you drive on are) but will result in premature engine wear & failure.

    The solution for the street crowd is a properly designed, good functioning oil separating catchcan. Many are available on the market, but you want one designed with internal baffling and a good distance separating the inlet from the outlet. Many of the cans seen for low prices on Ebay, etc. are great looking, but are nothing but empty cans with two fittings attached. Do your homework & get a full understanding before you make your selection."

  3. grumpyvette

    grumpyvette Administrator Staff Member

    What prevents the oil mist vapor being sucked out of the crank case by engine vacuum,from being siphoned back into the intake?

    the sudden change in air velocity , and direction, of travel,inertia, as a small passage emptys into a larger volume, plus baffles and or a mesh the micro droplets collect on




    keep in mind the brake vacuum to the brake booster is generally connected to the intake manifolds plenum vacuum, if you don,t have a proper PVC valve on the valve cover on at least one valve cover and a breather on the other valve cover you may have engine crank case back pressure reduce the intake plenum vacuum, reaching the brake booster reduced

    Last edited by a moderator: Mar 1, 2018
    Strictly Attitude likes this.
  4. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Found today Grumpy.
    Bring the old thread alive once again.
    Strictly Attitude likes this.

Share This Page