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L series - Positive crank case pressure, too much.


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I used a -6 check valve on my car. I made the block plug and it is installed with orings. The plug is tapped for the check valve. I then and this is important, drilled a .060 hole in the bottom of the plug to get the gases, but not fling any or little oil in the air path. from the check valve I then have the hose going to a seperation tank, and from the tank to the bottom of the intake manifold.

This setup has worked very well for me. I don't get the smoke on decell anymore and the engine seems like it likes it.

not the cheapest way to go, but fixed the problem.

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My friend is building me a catch can (hopefully will be done with it tomorrow). I'm going to plumb it with the block and valve cover going to it and the exit on the catch can going to the compressor inlet where it is always under vacuum.

 

Right now with both vented to air the car has stopped smoking on decel, so it was definitely related. I think my PVC is bad and was pressurizing the block or something, since it was worse under boost.

 

Mario

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I am having the same problem with my setup, although it is because very low tension oil rings were used. The solution is going to be to run a Camero LT1 electric smog pump and activate it with the same output from the AEM EMS used to run the methanol pump.

 

http://www.turbobuick.com/forums/general-turbo-buick-tech/234420-crankcase-evacuation-lt1-smog-pump-how.html

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My friend built me the catch can that Supra510 describes. I plumbed it up and everything seems like it working great. I need to double check when it's nice out as I have no traction in 1-3rd because of the rains.

 

510six, on the link you posted, the guy rights that it is too much vacuum to use the turbine inlet. What is everyone's take on this? I'm pretty sure my problem has been alleviated, after 30 mins of driving around there wasn't a hint of that annoying burning oil smell that has been plaguing my car.

 

When I removed my PCV, I blew into it the "wrong" way, and it did in fact leak. It seems like I was pressurizing my lower end.

Mario

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My friend built me the catch can that Supra510 describes. I plumbed it up and everything seems like it working great. I need to double check when it's nice out as I have no traction in 1-3rd because of the rains.

 

510six, on the link you posted, the guy rights that it is too much vacuum to use the turbine inlet. What is everyone's take on this? I'm pretty sure my problem has been alleviated, after 30 mins of driving around there wasn't a hint of that annoying burning oil smell that has been plaguing my car.

 

When I removed my PCV, I blew into it the "wrong" way, and it did in fact leak. It seems like I was pressurizing my lower end.

Mario

 

 

If the catch can is solving your problem I would stick with it, I don`t want to take the chance of oil ending up in my turbo inlet. The pump "should" be the right solution for me as for the very low tension oil rings being used. It will be a couple of weeks before I am able to install the pump.

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I think the key to this is that your catch can actually needs to "catch" something. A lot of can's don't have baffles or anything else in them to assist with removing the oil vapor and then it ends up in the intake. If you have a properly baffled can it minimizes any oil vapors.

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What does everyone think of this set up?

 

Valve cover open but filtered, the rest set up per the diagram below. I was thinking this would give good vacuum off boost through the manifold (when exhaust flow is low) and then once on boost, the upper PCV valve would shut, and the lower one would open, creating a better vacuum with the high volume of exhaust flow.

 

pcvdiagram.jpg

Or should I ditch the manifold PCV valve and just run the exhaust evacuation?

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For all those quick to dismiss 'rings' after only seeing a 10 psi rise, at sea level I have had engines with 180psi of compression smoke like a third-world mosquito-abatement fog generator under these same conditions!

 

Oil control rings don't do a damn thing for compression, and L-Engines are notorious for weak oil control rings. Only problem is the 'clean plugs' testimony. When oil control rings are bad, you will foul the plugs if the leakage is bad enough. I had a stuck ring on my #5 cylinder some years ago, and ended up trying to kill the engine running it like hell and beating it with well over my normal 12-17 psi of boost. After that track day....my smoking ceased. So did my plug fouling problem in #5.

 

If there is smoke in the exhaust, I guess my question would be 'how much oil are you consuming and under what driving conditions?' If is possible that you can have clean plugs and still be sucking down oil past the rings... My 75 runs through about a quart between 500 and 1000 miles but the plugs are clear and nice light tan. You see it occasionally, you smell it if you are following me, you may even get bits of oil to rustproof your car...but the car has 180psi of compression, dynos to 147 at the rear wheels, and has 225K+ miles on the engine. I don't worry about it, I don't worry what everybody says about it...it runs strong, quiet, and simply uses some oil. One day I may go in and install some valve guide seals because I bought some for it...but it's not imperative I do so.

 

So how much oil are you consuming...I haven't seen any quantification. Just a complaint of smoke out the tailpipe. If you evacuate your PCV to the tailpipe, it can smoke there as well...

 

I'd be curious to see what pressure is in the crankcase during the smoking excursions. Many times restricted breathing can cause the pressure buildup and cause leaks/smoking. A catch can in many cases simply adds adequate volume so that the flow of the blowby doesn't pressurize it to a point where it will cause a problem. One with a coalescing element (steel wool looking stuff) helps when there is too much evacuation and the velocity keeps oil vapors entrained in the air---the wool gives the oil something to stick to and drop out of the airstream.

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haha that made me laugh.

 

remember to mount that PCV tube on the downpipe at a 45 degree angle =)

 

heh, I didn't know what to call it.

 

And getting it at 45 degrees is going to be a little bit of a challenge. Because of the way my dump pipe is made, it has to go in the first bend as drawn.

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  • 8 months later...
What does everyone think of this set up?

 

Valve cover open but filtered, the rest set up per the diagram below. I was thinking this would give good vacuum off boost through the manifold (when exhaust flow is low) and then once on boost, the upper PCV valve would shut, and the lower one would open, creating a better vacuum with the high volume of exhaust flow.

 

pcvdiagram.jpg

Or should I ditch the manifold PCV valve and just run the exhaust evacuation?

 

I like this layout. It would be even better with a small, sealed catch can after the block breather. I would also play with an adjustable restrictor on the valve cover port, to modulate the amount of flow/vacuum inside the crankcase. The more you would restrict the valve cover breather, the higher vacuum you can pull in the crank case. You dont want too much, but you want it to be enough vacuum to be horsepower beneficial, yet still have enough flow to clear out the light gasses without sucking out heavy oil mist.

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Actually just worked on an F-350 today that had a very similar problem. My shop's several-thousand dollar test equipment said there were no problems with vacuum or crankcase pressure, but there was still smoke in the exhaust. Turns out the oil drain line from the turbo had gotten blocked due to oil coking because of the high temps caused by an aftermarket chip controller, and wasn't letting the oil out of the turbo... just an idea.

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I agree with Jon and Tony, don't dismiss those rings so easily. My last engine began smoking on decel and consuming oil. Compression tests were strong and even, leakage tests less than 5%. After performing every test I could think of several times with different testers (to rule out faulty equipment) I concluded it MUST be the rings. It was. Engine back together with no smoke/oil loss.

 

I do not run a pcv, both breathers run to a catch can with a vent on top. Been running this setup for over ten years with no problems and zero leaks. My .02, good luck.

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I used the above diagrammed system with the exception that I put the PCV valve on the block vent after passing through an air/oil separator. I plumed the valve-cover top vent to the exhaust venturi.

 

I was running a cheapo muffler that was fairly restrictive at first. It still pulled vac on the system. The vacuum was significantly improved when I installed a turbo muffler.

 

I also connected the original tank breather vent valve in it's original configuration.

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Check this out.

 

http://www.pitstopusa.com/detail.aspx?ID=61724

 

Seal off the crankcase to vacuum, provide a vacuum source from, pump, intake, and/or a venturi tube in the exhaust. Then regulate the vacuum with that regulator. It should give the ideal conditions for PCV control vs aerodynamic advantage inside the cankcase. Dial in the right amount of vacuum without sucking in oil seals or sucking out excessive oil.

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