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1980 L20b Crankcase breather mesh missing


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   So going down the highway the other day and my engine started missing pretty bad around 70. got home, did some work found a lot of oil in the intake. Long story short I tracked it back to the vent tube that comes out of the crankcase and found that the screen that is supposed to be in the case to keep oil from going into the intake wasn't there. Instead I found that the person who had the truck before me had used a piece of burlap which obviously has deteriorated at this point.

   Now i was figuring I can replace it with some window screen I've got laying around but my question is, how are you supposed to put it back in there? I'm assuming from the looks of things i'll have to drop the oil pan to get to that spot but i'm not sure. Can't find anything on the internet where someone else has had the same problem. Any help would be greatly apreciated  

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What he said. The mesh isn't the same as the baffle. It won't keep the oil from puking.

 

If I were going to replace it, I sure as hell wouldn't use window screen or brillo pads. I would go to my local Nisan dealer and have the correct part ordered for me.

 

I usually replace those 6mm screws with 6mm bolts, to make them easier to remove in the future. And use red loctite on them when assembling.

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I'm betting the Nissan screen... is fly screen. It slows the fog of oil droplets and gives them something to cling onto. Droplets form that are too heavy to get sucked out and they dribble back into the pan.

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I'm betting the Nissan screen... is fly screen. It slows the fog of oil droplets and gives them something to cling onto. Droplets form that are too heavy to get sucked out and they dribble back into the pan.

It is, but it's folded over 8 or 10 times and held together with soldered wire wrapping around it. Stuffing a regular wire mesh in there is not a risk I would be willing to take. For the $15 the OEM part costs, the price for failure is too high.

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Quick and dirty, use stainless steel "Brillo" repalcements where the burlap is, then do it right!

 

I use this anyway, even when I'm building an L4 from scratch.

Takes about 2 full SS scrubby pads, and could be packed in through the breather hole.

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You can do this if you want but never suggest this to others. There is no advantage to removing it.

 

Before '62 cars just dumped the fumes and blow-by (mostly water vapor and unburnt gas) from the valve cover under the engine onto the road. Every night when the engine cooled the remaining blow-by would condense and add to the oil. Oil changes were required much more oftener back then because of the dirty oil and also, engines were lucky to get over a hundred thousand miles on them. If you have an older engine with lots of miles and it 'burns' oil you don't want it dirtying your oil.

 

The PCV system is absolutely benign in operation. Has no effect on running or performance but keeps your engine insides and lubricating oil cleaner for longer. The PCV is a one way valve the uses a small amount of intake vacuum to draw fresh air into the valve cover to replace blow-by fumes sucked out of the crank case. If the hose to the PCV fails...the engine won't notice, it just keeps running. If the PCV sticks closed, the same. Simple and fool proof

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The PCV system is absolutely benign in operation. Has no effect on running or performance

While I appreciate where you're coming from, I just can't allow this statement to be perpetuated.

 

It does affect tuning. It is a vacuum leak. You can tune around it, but it is not benign.

 

Don't misunderstand me. I do like to have a working PCV system, but it should be understood to get the most out of it.

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I'll get hated on for this, but take all that shit out and put a frost plug in where the breather tube is. Yes no pcv, but problem solved

Depending on what you're trying to achieve, this is a possibility. I still like to have a block breather on street cars, no matter how they're tuned, but on a race car, it does get plugged.

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While I appreciate where you're coming from, I just can't allow this statement to be perpetuated.

 

It does affect tuning. It is a vacuum leak. You can tune around it, but it is not benign.

 

Don't misunderstand me. I do like to have a working PCV system, but it should be understood to get the most out of it.

 

 

Yes it is a designed around and taken into account leak.... and very small. Idle mixture adjustment can cancel it out. At wider throttle openings (and lower intake vacuum) even less air gets in.

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