L20b PCV / crankcase ventilation question

[Silky_Johnson]

I would cross drill from each end....not going through (each) the 2nd runner.

Cap the 2 holes just drilled

[img=http://i1007.photobucket.com/albums/af197/MattStoffregen/Datsun/Cannon_Manifold_Cross_Drilled_zpsfb87dc17.jpg]

 

Then.....drill 2 holes into that 'bar' between 3 and 4....1 and 2

....Fittings and hose to a tee in the center......<.....PVC...

 

(Inserts question mark)

This makes sense to me.

[Stoffregen Motorsports]

I would cross drill from each end....and not go through the 2nd runner into the middle bar.

Cap the 2 holes just drilled

 

Then.....drill 2 holes into that 'bar' between 3 and 4....1 and 2

....Fittings and hose to a tee in the center......<.....PVC...

 

(Inserts question mark)

Why wouldn't you drill all the way through? The center section would be the "tee" as you describe it.

[Stoffregen Motorsports]

Wikipedia is not always correct, but on this topic - I think they have it right.

In it they give you the principles behind it and the history - it's a good read.

 

Quote from Wikipedia: The PCV system is not a classical "vacuum leak".

http://en.wikipedia.org/wiki/Crankcase_ventilation_system

That is correct, but for this argument, it is a vacuum leak in the sense that it introduces a non-regulated source of air into the induction stream behind the fuel/air metering device (carburetor). The point is, you have to tune around it, and that is not always easy. Remember...splitting hairs.

[Sealik]

Why wouldn't you drill all the way through? The center section would be the "tee" as you describe it.

 

An open center section 'compliments' 2 and 3

 

 

 

Also....you wouldn't have to drill right though the whole IM

More of a balanced flow...you would creating a vacuum leak on the sides of ....basically 2 runners..?...., compared to the two ports on top between all 4 runners.

[Stoffregen Motorsports]

Remember, only one cylinder pulls at a time. I think the tee would not be any different, better or worse, than drilling all the way through. I like a clean engine bay so I would drill and not have to see any auxilliary tubing.

[Xnke]

The PCV system is NOT a vacuum leak, and you don't have to fight it with tuning. It simply ISN'T a vacuum leak!

 

Whether you take it to the intake or not, that's your decision, but you DO need a functional PCV system or you will end up with filthy oil and oil leaks everywhere.

 

The PCV valve is a vacuum regulator...under high-vacuum it closes up nearly shut, and under WOT it's completely closed...Take one apart and look at it, it's ingenious how they put one together. A properly functioning PCV valve will hold a relatively constant vacuum pressure on the block side of the valve, with a varying flow rate.

 

If your PCV valve is in good shape, and your engine doesn't have huge amounts of blowby, AND your engine block filter screen (inside the block) isn't covered in shitty, nasty oil from years of neglect, then you won't have very much gunk getting blown into your intake manifold to reduce the octane number of the intake charge. You're not leaning anything out, you're reducing the octane number by introducing oil vapor. If you're worried about it, run one grade higher gasoline, or pour a gallon of tolulene into the tank with 9 gallons of 93.

 

If your PCV valve is garbage, replace it...it's a three dollar part. If your engine has huge amounts of blowby, It's time for new rings, don't band-aid it. If your engine block filter screen is shitty, remove the oil pan and undo the one JIS/phillips head screw and take it out, clean it, and put it back in.

 

As for where to place the PCV valve, I'd do what Stoffregen Motorsports said, and drill the vacuum log. I'd then drill and tap in the middle to install the valve, as this is exactly how I did it and how several other OEM's did it. (Nissan, Toyota, Mercedes, BMW)

[Stoffregen Motorsports]

The PCV system is NOT a vacuum leak, and you don't have to fight it with tuning. It simply ISN'T a vacuum leak!

 

Whether you take it to the intake or not, that's your decision, but you DO need a functional PCV system or you will end up with filthy oil and oil leaks everywhere.

 

The PCV valve is a vacuum regulator...under high-vacuum it closes up nearly shut, and under WOT it's completely closed...Take one apart and look at it, it's ingenious how they put one together. A properly functioning PCV valve will hold a relatively constant vacuum pressure on the block side of the valve, with a varying flow rate.

 

If your PCV valve is in good shape, and your engine doesn't have huge amounts of blowby, AND your engine block filter screen (inside the block) isn't covered in shitty, nasty oil from years of neglect, then you won't have very much gunk getting blown into your intake manifold to reduce the octane number of the intake charge. You're not leaning anything out, you're reducing the octane number by introducing oil vapor. If you're worried about it, run one grade higher gasoline, or pour a gallon of tolulene into the tank with 9 gallons of 93.

 

If your PCV valve is garbage, replace it...it's a three dollar part. If your engine has huge amounts of blowby, It's time for new rings, don't band-aid it. If your engine block filter screen is shitty, remove the oil pan and undo the one JIS/phillips head screw and take it out, clean it, and put it back in.

 

As for where to place the PCV valve, I'd do what Stoffregen Motorsports said, and drill the vacuum log. I'd then drill and tap in the middle to install the valve, as this is exactly how I did it and how several other OEM's did it. (Nissan, Toyota, Mercedes, BMW)

You do have to tune around it at idle. And when the weather changes from 50 degrees to 100 the PCV makes tuning all the more required.

 

We are striving for perfection...right?

[ericsb210]

Just a thought, run the PCV valve to one fitting on a device such as a water separator for a  compressor and connect the other fitting to the intake for needed vacuum. Would this not keep the PCV working in proper order (as originally intended) and also keep any oil or other contaminants out of your intake. NOTE; make sure you keep an eye on the container and empty when necessary. 

 

And than run the valve cover breather through its own filter.

[AZhitman]

I wound up plumbing the engine block vent into the manifold, via a PCV valve.  

 

For now, the valve cover port is simply connected to an open length of hose running down past the trans tunnel, but I'll likely switch that out to a vented catch can later (if only to keep my pristine undercarriage clean).  :)

[Rocket Dog]

Good morning.  Re-visiting an old thread with a fundamental question.  Here's a couple of pics of the "as is" set up.  L20B motor in a 72 521 truck.  I don't have a PCV valve and of course I get oil mist etc in the engine compartment.  It also will diesel from time to time when I shut the engine off.  That may or may not be related to not having a pcv, but the question is this.

 

I purchased a Fram PCV valve and notice one side is threaded.  Do I just ignore that and just stick it in line, slap a couple of hose clamps on, or should I have some other fitting that screws in to the pcv valve? I have a Weber carb, and the hose runs from the valve cover fitting down to the base of the carb, and also to a fitting that ties in with the evaporator (?) tank mounted in the truck bed, above the gas tank, under the fender well.  I'm not sure how all of that works together but my interest is in making it function normally.  Thanks again.

 

 

 

[DanielC]

If it is the correct PCV valve for a Datsun L-engine, it should screw into the port on the intake manifold pointing to the rear of the truck.

 

For the evaporative emission flow control valve. see this picture.

If you look at the valve, there is an "A", a "F" and a "C", from the top.

"A" goes to the inside of the Air cleaner.

"F" goes back to the Fuel tank, but actually is in the top side port on the liquid separator tank, above the gas tank.

"C" goes to a small pipe on the side of the big PCV pipe coming out of the Crankcase, under the manifolds. 

There is no charcoal cannister.  Gas vapors are stored in the crankcase of the engine.

Flow will go down in the valve.  If there is a vacuum in the tank, air flows from the air cleaner into the "A" port, and out the "F" port.

If there is pressure in the tank, fuel vapors are pushed in to the "F" port, and out the "C" port to the crankcase.

 

Note, the hose on the valve cover, that goes to the underside of the air cleaner, prevents any pressure from building in the crankcase.

[banzai510(hainz)]

Daniel has it right for the stock aircleaner set up.

 

I myself dont reallkky use the evap system except :this one below

"C" goes to a small pipe on the side of the big PCV pipe coming out of the Crankcase, under the manifolds.

 

 

cant really tell by your photo but the crankcase should go to the PVC valve under the intake manifold.

 

 

I run the valve cover to under the carb as you have photo also.

 

 

that elbow comming ou the lower manifold goes to what?Most people plug this now. if you get overspay soemtimes you not venting correctly.

 

 

open chamber l20 will desiel if no shut off seliniod on Weber.

You like you got a Manual 5A type with a choke wire going to pass side of truck?

[tr8er]

 

PCV threaded into intake manifold. Hose connected to crankcase vent pipe. I fit the hose into the vent pipe and over the PCV. It works.

[tr8er]

[Rocket Dog]

Ah okay, I have some homework to do.  B)

 

Okay, I found it.  Apparently I have a PCV valve but it's probably been there since Hitler was a corporal.

 

[datzenmike]

Have a care removing that braided hose. It can't be replaced... easily... one end is larger than the other... figures.

[banzai510(hainz)]

where are the other 2 lines going to? the ones that go to bottom of the page. I dont run them

[Rocket Dog]

where are the other 2 lines going to? the ones that go to bottom of the page. I dont run them

The lines at the bottom run to the little (manifold) that connects to the tank in the truck bed under the driver side fender well. I'll post another pic.  In the pic below in the lower center is the evaporative emission flow control valve that Daniel posted above.  It's dark, hard to see. 

 

 

 

 

[Nuclear Water Boy]

Do it right the first time, but you must pick which way to do it so here you go.

 

http://www.motoiq.com/magazine_articles/id/2032/pageid/3345/crankcase-ventilation-explained--na-edition.aspx

[banzai510(hainz)]

OK the bottom hose that goes to C on the emission control valve will go to the crank case tube.in your photo it goes to a T with one side blocked off and the other to the carb.This is WRONG as I know of.

 

look at Tr8ers photo of his cranse case BIG tube youll see a small outlet underneath. thas what hooks up to C of the emission valve.

 

I just plug that lower hole under carb. with a rubber cap

 

end the end will this matter? I have no idea. On my 510 these are not used as I have sidrafts.

On my 521 I run "C" but the yop hose I dont run and its fine.

 

most PCV valve you can just clean in solvent. it just a metal block the slides in the tube.