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Oil spooging L20B

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So I ran the 510 all winter with no problems. Running 10w30 Royal Purple, and lots of screwing around. Now that it's gotten slightly warmer, I switched out to 10w40 Royal Purple and have been doing highway driving. Around town is fine, but with sustained 6-6500 rpm jaunts, oil begins to spooge out my crank breather just a little bit.


I have it running from the breather tube, around and down to a vent with a breather filter next to the air filter. The valve cover breather goes to the PCV valve in the intake.


The setup is exactly opposite on the D21. It sucks from the breather on the block, but the plate that covers that is also much more involved. On the 20B, it's easier for oil to get around it. I know this is a common problem on 20B, the reverse setup usually results in some smoking from oil burning on high rpm shifts and decels.


Besides a catch can, does anyone else have a different setup that keeps the oil from overflowing?

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I had it this way before, still had some issues. Just burped occasionally from valve cover vent instead of block vent. It also tended to siphon oil out of the crankcase that way. I can't remember how much though. I may re-route it just to try, I'm inclined to agree with that routing. Seems either way abusive high rpm running wants to eject oil here and there. I'm not talking a lot, but even a tablespoon of oil running down the fender apron is really annoying.

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Clarification Mike, are you saying one vent or two into the catch can?


Connect the block vent (pipe behind the exhaust manifold) back up to the PCV valve on the intake. This is how the factory system is set up. Valve cover vent to a long hose and down low to a catch can. A long hose so it collects more of the spray/vapor and also so any fumes are drawn under the car and you don't have to breathe them.

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Why not a catch can up high so it can drain back into the crankcase?


I didn't think the catch can was so designed that it had drain back. It's more like the can that catches grease on a bar-b-q. Race cars often have to have them to catch the oil from exploded motors and keep it off the track.

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I started reading up on catch cans, this excerpt from Perrin's website:


Blow-by is a constant problem with any turbocharged engine. While a normal byproduct of the combustion process if it isn’t contained outside the engine it will collect and gum up the valve train, turbo and most importantly the intercooler and plumbing. When this occurs it reduces the thermal efficiency of the intercooler, thus losing power and performance. With our cleverly designed and easy to install silicone catch can you can control this problem. Available in red, blue or black silicone body to compliment any engine bay. Universally designed to work with all turbocharged applications.


Lets look at your engine for a moment. Every engine during the normal combustion process, has blow-by. Engine Blow-by is excess combustion gases that leak by the piston rings and escape into the engine crankcase. During each compression or power stroke of a normal engine cycle, a very small amount of gases leak by the piston rings. This happens because the piston rings do not create a perfect seal. This Blow-by of gases is very small, but the higher the RPM and the more pistons, the more the blow-by starts to create pressure in the crank.


This pressure needs to be released, and is done so by crank case vents. Because manufactures have to keep environmental issues in mind, these gases can’t just be vented to atmosphere. So the OEM’s vent these gases back to the intake system to be re-burned. This all sounds good, but Blow by is nasty stuff!


Engine blow-by contains gases and oil from the crankcase. The gases aren’t really a problem, but the oil is. This oily mess coats everything in its path as it makes it way back to the combustion chamber. This nasty oil mess gets into the turbo, then boost tubes,then intercooler, into the intake manifold, and finally back into the engine. As the oil creeps in between couplers and boost tubes, it can cause the connection pop off under boost. This oil then gets into the intercooler, coating all the cooling fins. This greatly effects the ability of the intercooler to cool, and the efficiency of it will drop! This will cause a huge loss in power and can cause detonation. The last place this oily mess sees before the combustion chamber is the intake valves. Because of the temp differences and the oil impacting them, the oil will start to build up and form sludge. This adds up over time, and can cause many other problems, and hurt performance.


From this you can see, blow-by is bad, and it needs to be dealt with.


Ignore the shameless plugs since it's from their website, but I understand the basic idea of it now. However, it seems my problem is slightly different as it's spooging a larger volume of oil. So step one is to reroute the lines similar to what I have on the KAZ24 motor, and then I think I'll put some baffle material in the upper valve cover breather tube before it goes out to the breather filter. This should provide additional mass to trap the majority of the oil, and only have vapor escape.

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I'm just going to make one, f that $150 for a stupid can. I have a mason jar, it'll work fine! ;) Okay, no, I'll use something plastic probably, glass is a little risky.

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I'm just going to make one, f that $150 for a stupid can. I have a mason jar, it'll work fine! ;) Okay, no, I'll use something plastic probably, glass is a little risky.


Why not just pick up a cheap ebay one? huh.gif Around $40 shipped usually. May not be name brand, but they look good and they work.

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Excessive blow by is causing the pressures inside the crankcase to build up. You probably knew that. Those excessive gases should be used to push the piston down.

Reality is the rings are starting to wear. That is the problem. If you are racing, you are wasting power the other guy in front of you is not. If it is a street daily driver, you are wasting gas. At around $4.00 a gallon.

Redo the rings, and get the blowby down to what the PCV valve can handle.

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The PCV valve has very small orifice, or the manifold have a massive vacuum leak. At idle and low speed it vacuums up most of the blow by and draws in fresh filtered air, but under heavy load the system backs up and gasses flow bacbwards out the valve cover hose. This is why it normally goes up inside the airfilter and gets sucked down the carb. Unless the blow by is severe and spitting oil I don't understand why people put those small blue filters on the end. The fumes just exit under the hood and can get into the cab.

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Shouldn't be ring blow by, the motor has less than 10,000 miles on it. I think the reversal of the pcv breather is one of the culprits. The reason for the filter on the end is just in case it manages to reverse flow when the engine stops, or during decel, you don't suck dirty air into the crankcase.


When I get done with the heater core, I'll reverse the system and see how it does. I had it that way once, can't remember the exact reasons for switching it, but either way, I think the motor is fine. It better be, I built it! ;) Would have liked to have done gapless rings, but used good quality Hastings rings, had the right end gap. Maybe the next engine build.


I think the big thing is if I put a secondary breather filter at the end before the filter, that should take care of spooging. Rather like what the stock carbed engines have. The tube ends with the fiber mesh material that eliminates a lot of the oil. Not all, but having that mess before the outlet should contain the burping problem.

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