Help with an L20B breather question

[delariva]

Hi guys,

I've been browsing the forums for a while now, and doing some research while looking for a 510. I am heading to check one out tomorrow afternoon. Everything looks good, but I have a question on what to look for regarding an oil leak.

Here is the quote from the ad:

"No fuel leaks, and I've had the rear main seal replaced which was majority of oil leak, but it still has a small leak from back pressure due to there not being a breather on top of the valve cover."

 

I am not sure what he is talking about. In the picture of the engine bay he sent me I see a tube coming off of the valve cover, isn't that the valve cover breather?

When I was researching this I saw a lot of posts for the breather from the block to the PCV into the intake manifold. Does the valve cover need to be routed somewhere as well?

 

sorry if it's a dumb question. The only other experience I have was when I restored a 1967 cougar with a 289. I was 15 then and my dad was helping me so I'm still pretty new at mechanical stuff.

 

 

Any help would be appreciated.

Thanks,

Nick

[delariva]

Also, I have read all the posts I can find here on ratsun. Like this one http://community.ratsun.net/topic/31062-oil-spooging-l20b/page__st__20 If I ran a longer tube from the top of the valve cover to a catch can like this suggested would that help with the back pressure he mentioned?

[Guest Rick-rat]

The hose on top of the valve cover used to go to the air cleaner when it had stock carb on it. Most people just put one of those cone shaped small filters on the hose. Looks like your filter only a lot smaller. just about any auto parts store have them

[delariva]

Thanks Rick-rat. So if that is taking in air (just not filtered right now) what would be causing a pressure oil leak? Is the block most likely not vented properly?

[screamer510]

http://community.ratsun.net/topic/38905-l20-rebuild-questions/

This is where I'm at, with similar problems. Look on page 2 for the root cause of my problem.

 

Dan

[Guest Rick-rat]

It does not take air in itwas supposed to go to the stock air cleaner to be run through the engine again, a filter on just keeps stuff from going in the valve cover. check pics in engine section "your engine bay" and you will see the filter that i am talking about. that shouldn't cause a pressure oil leak

[datzenmike]

The PCV valve uses a small amount of intake vacuum to suck crank case fumes (warm fuel and water vapor and combustion blow-by gasses getting past the rings) and runs them through the combustion chamber to burn them up. The air removed from the crank case is made up by filtered air from the breather on the carb and is drawn in through that hose on the valve cover. At idle and low speeds this is how it works. At higher speeds the engine vacuum is lower and the motor may produce more blow-by than can be drawn into the intake by the PCV valve. In this case the air reverses direction and flows out the valve cover hose and into the air filter housing where it is sucked into the carb.

 

The PCV valve is essential for removing water and gas vapors from the crank case where they would normally condense when the motor cooled. The PCV valve increases the time and mileage between oil changes by keeping the oil cleaner and free of contaminants and dirt for a cleaner motor.

 

I would find out if that intake has a PCV valve on it or is the hose just hanging off the side of the block.

[banzai510(hainz)]

I would just route a longer hose down towards the block is what I do.

 

the block crank case I just vent out. since you got sidedrafts.

 

I would clean up that wiring by the coil and the wire goin across the carbs.

[delariva]

Thanks for the advice guys. And thank you for the explanation datzenmike that helped a lot. Always learning somemething new on this site

[IrvinM]

So you don't need that thing!? I purchased a PCV valve at Autozone and was puzzled since I thought it would fit right into the hole in the valve cover. It did not, it is too small. the part number on it is PCV1142 from Luber finer. I have no idea where it goes. This is for my 1975 Datsun 620 with the L20B

[EricJB]

I think we've done the pcv thing to death the last month or so. Lots of info/ arguments on this. You don't even have to search, just go back a page or 2.

 

I think the consensus is, if you drive it daily, and don't want to change the oil a lot, figure out a way to retain it.

 

 

[K_trip]

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