Jump to content

L20b PCV / crankcase ventilation question


AZhitman

Recommended Posts

  • Replies 94
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

I do not understand the point of having two hoses if no PCV valve is being used, the inside of the valve cover and the inside of the case is the same cavity, the big difference between them is the case vent has a screen to keep the oil inside the case, while the valve cover is just a hole, the valve cover cavity is not going to build up any pressure, as that will be relieved threw the case vent.

I do understand why you need the valve cover vent when the PCV valve is being used, it is a vent that works both ways, as the PCV valve only sucks in a certain amount of air, and the rest is relieved(in or out) threw the valve cover vent.

The old chevy 283/327s had only one case vent as I recall before the PCV valve, the oil filler tube on the front of the intake manifold, and the cap had a screen to keep the oil in the engine.

Link to comment

OK, do these manifolds have any access ports you are not using of any size?

Is there a balance tube?

You don't necessarily have to have a big hole, you can use a small line with a fitting that has an adapter that will allow the PCV valve to be screwed into, someone on this thread posted a photo of a remote PCV valve.

I am not saying this will work either, but if the access fittings are large enough, they will act as a balance tube also.

Both them manifolds must have at least one access hole.

 

EDIT, I forgot you don't want anything going into your intake, so maybe someone out there has done the same thing using some kind of electric air pump on the engine case vent.

Link to comment

This is basically what mine looks like: o142448401.jpg

 

Except mine doesn't have the port tapped.

 

I'm just thinking that our gas is crappy enough in AZ as it is... I'd like to avoid diluting the octane with any oil / vapor / whatever.  

Link to comment

I would look in to some kind of some low CFM air pump that sucks, and run it to a catch can, then exit underneath the car beside the tranny to reduce the fumes.

Unless you use some kind of circulation in the case, you are just going to end up with a mess inside the engine, and you would know what I am talking about if you ever tore down an engine without a PCV valve.

Them engines back then did not last, they were just about wore out at 100,000 miles.

Link to comment

If you are worried about oil vapors going into the intake manifold, and in enough of a quantity to cause the octane rating of the fuel to drop, or "gunk up your engine", you have enough blowby to need the rings replaced.

 

I know replacing the rings requires a lot of work.  It is not "sexy" nor does it do any thing to look better in the engine compartment.  They are totally hidden from view.

 

But good sealing rings prevent most of the blowby.  Blowby is lost gas pressure that is just wasted, that is not available to push the piston down on the power stroke. 

 

Here is another thought.  Probably more oil get into the top of the cylinder from the rings, and the valve guides.  In both cases, as the engine wears, the oil getting sucked past the rings on the intake stroke, and the valve guides, increases as the engine wears.

 

On engine with good rings, and a good PCV system, the crankcase is at a slight vacuum, most of the time.  Lower pressure in the crankcase means less oil leaking past the rings, or valve guides.   It also means less external oil leaks.

 

One last thought.  A major part of blowby gasses is gasoline vapor.  This vapor is caught, and rerouted back into the combustion chamber by the PCV system.  If you change nothing on the carburetor, that means a slightly richer mixture.  Richer mixtures means more power, and this gasoline vapor is just lost without a PCV system.  Or you could tune the carb for the blowby, and get better gas economy.

  • Like 1
Link to comment
Great info, guys.  The setup that Stoffregen is using is pretty much what I had in mind.

 

However, I don't want it venting near the cowl and potentially stinking up the interior - Plus, I don't have a cool can like that one.   :)

 

I'm really leaning towards simply running a hose from the valve cover port and the crankcase port, into a T, then extending a single line down next to the transmission with a breather on the end.

 

Is there any reason I can't / shouldn't do it this way?

Without reading through all the replies to this question, I will add;

 

I don't like PCV because it is a vacuum leak in it's nature. If you are running a stock'ish motor, then this doesn't matter too much, but if you've got a big cam, dual carbs, etc. I would NOT run the PCV, or at least make the orifice very small, like .100" or smaller. The tee into the air cleaner (top or bottom) does vent to atmosphere, but also benefits from light vacuum which will cut down on the stink.

Link to comment

As Wayno mentioned, there are small vacuum pumps that pull the bad stuff out and dump it into a puke tank. But thats mostly for full on  600+ cid turbo setups and crazy shit like that. Where is your muffler? You could put a evac valve after the muffler to draw it out.  All you need is one bung and check valve ( they sell seperately) drill a hole in the pipe after the muffler, weld it in at a 45, and plumb it to the block vent. put a filter up top and your done.

MOR-25900_YJ.jpg

Link to comment

If you are worried about oil vapors going into the intake manifold, and in enough of a quantity to cause the octane rating of the fuel to drop, or "gunk up your engine", you have enough blowby to need the rings replaced.

 

I know replacing the rings requires a lot of work.  It is not "sexy" nor does it do any thing to look better in the engine compartment.  They are totally hidden from view.

 

 

Fresh build, big cam, dual carbs.  Rings are new.

 

I don't sweat the "work" involved, and I'm not much of a "form over function" guy (but I do like my cars to look nice).  Functionality, reliability, and usable power all come first.

 

I suppose I could tap both sides of the manifold for a tiny line to provide vacuum for the crankcase, but I'm not too excited about it at all.

  • Like 1
Link to comment
As Wayno mentioned, there are small vacuum pumps that pull the bad stuff out and dump it into a puke tank. But thats mostly for full on  600+ cid turbo setups and crazy shit like that. Where is your muffler? You could put a evac valve after the muffler to draw it out.  All you need is one bung and check valve ( they sell seperately) drill a hole in the pipe after the muffler, weld it in at a 45, and plumb it to the block vent. put a filter up top and your done.

MOR-25900_YJ.jpg

 

This is the way I would go if your not going to use a PCV valve, and all the smell would go out the back, and IMO you need the check valve.

Link to comment

Just run it open. People have been doing it for decades.

 

If you see some oil leaking or even see wetness forming around the seal areas, then consider some kind of an evacuation system. But for now, if you're car is going to look like yours normally do (super clean and well detailed), forget it.

 

Once you tap the manifold, you'll always see it. There's that joke about women and light bulbs...you can unscrew a light bulb. Same here, once you drill and tap, you're stuck with it.

Link to comment

 

BTW- you have a 67.5 Roadster ?

 

2000 ???!!!

 

Impressed.

 

The 67.5 SPL311 came originally with the 5 main bearing metric R1600. I believe that he has installed a stroker and increased the displacement to 2 liters. Better performance with the original block & looks of the original 1600cc R engine

Link to comment

SPL = R16

SRL =U20

 

I'm no roadster guy, but my buddy is, so I am been reluctantly educated.  I do want to stroke my 411sss R16 to a 2.0 though. You either use a U20 crank with the nose cut off it, or an H20 crank from a forklift, I think. 

Link to comment
Just run it open. People have been doing it for decades.

 

 

 

 

Yes they have, and up until the 60's most everyone did but motors sure didn't last long back then and oil was changed every 2K or sooner. You would indeed be very lucky to get 100K out of a motor back then. Take a '50s motor apart and it's black as the ace of spades inside. There's no advantage to not running a PCV on a street car. Most racing modifications don't translate well for the street and running a catch can instead of one is like running a spoiler, hood scoop, or drilled rotors. As to the drilling of the intake, do it on the bottom where it can't be seen then and screw in a valve..... or not.

Link to comment
 

Yes they have, and up until the 60's most everyone did but motors sure didn't last long back then and oil was changed every 2K or sooner. You would indeed be very lucky to get 100K out of a motor back then. Take a '50s motor apart and it's black as the ace of spades inside. There's no advantage to not running a PCV on a street car. Most racing modifications don't translate well for the street and running a catch can instead of one is like running a spoiler, hood scoop, or drilled rotors. As to the drilling of the intake, do it on the bottom where it can't be seen then and screw in a valve..... or not.

You are right, but you're forgetting one extremely important point; oil has changed drastically over the fast 20 years. Also, if it is not a daily driver, I would chose aesthetics and tradition over a questionably modern emissions control device.

 

And I obviously don't agree with your assessment of performance advantage. The vacuum leak introduced by the presence of a PCV valve can be hard if not impossible to tune around. It just introduces another variable to the mix.

Link to comment

Oil still abosrbs water and makes acid just as bad as it did 20, 30, 40  years ago.  PCVs have been around for 45 years, it's not a questionably modern device.

 

Catch cans are a Model-T solution.  They deserve to go in the history books along with cup-and-splash-lubricated crank bearings.

 

Overly finicky high-end racing carbeurators on a street engine are great for those trying to impress folks with the size of your wallet, but it's useless for real world.  A carb that can be used on the street can handle a PCV.  Keep the catch cans on the track where they belong.  I can understand their purpose when you're running at 100% horsepower and need every ounce.  Not needed so much slogging through stop and go traffic...  especially having to breathe the vapors from said catch can.

 

Oh, and I'm not saying I've never run a catch can.  Well, on the engines I deal with, we call them puke tanks.  They're 5-gallon tanks and I've had to draw over 3 gallons out of one after a days running.  Not good, because a half gallon sloshes around in the turns and can make a mess.  Of course the oil capacity of that engine is 12 gallons... of 70 weight Bardahl.

Link to comment
  

The 67.5 SPL311 came originally with the 5 main bearing metric R1600. I believe that he has installed a stroker and increased the displacement to 2 liters. Better performance with the original block & looks of the original 1600cc R engine

 

Correct.  I have a stroker in the Roadster as well as in my WRL411 SSS.

Link to comment

It appears this has generated some disagreement... Hopefully, it'll be a helpful thread for future generations of Rats.

 

Unfortunately, I'm still at a loss.  Mike, I can't run anything on the bottom of the manifold.  As best I can tell, my carb heat shields and header are relatively close, making it cramped quarters under there.

 

If I were to bite the bullet and fab up a balance tube (and drill / tap my pristine Cannon manifold), should I connect the crankcase vent ONLY to it, and run a breather on the valve cover port?

 

Or do I need to go full-bore with a PCV valve off the valve cover port and plumb it into the balance tube as well?

 

Sorry if I'm being dense - I'm not coping very well with the idea of a bunch of 80's-era plastic and rubber crap draped over my fresh engine.  :) 

Link to comment

 

SPL = R16

SRL =U20

 

I'm no roadster guy, but my buddy is, so I am been reluctantly educated.  I do want to stroke my 411sss R16 to a 2.0 though. You either use a U20 crank with the nose cut off it, or an H20 crank from a forklift, I think. 

 

The NISMO catalog lists the R16 stroker crank as part number 12200-E0700 and states you need 4 U20 connecting rods part number 12100-25500. Also lists U20 connecting rod bolts [NLA by the way] as 12109-25500 and con rod nuts as 12113-25500. Good luck on the search, the upgrade is worth it [even though I have kept my engine as stock can for 45 years].

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.