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PCV or fixed orifice
Posted by: KenHenry ()
Date: June 27, 2022 09:04AM

I have the heads removed from my recently rebuilt engine and it looks like I am drawing excessive oil into the combustion chambers, probably through my DIY PCV system. The PCV valve is seated in the stock coupling on the right side of the sheet metal top cover (maybe too close to the oil storm inside the crankcase??) and "venting" is through a hose running from the oil fill tube to the air cleaner. The oil fill tube is baffled and I see no evidence of oil getting through to the air cleaner. So I think the oil consumption is through the PCV line.

One option would be to install some kind of oil catch can in the PCV line. Alternatively, I am considering going back to the fixed orifice system but am unsure what to do with venting? The factory placed the vent in a way that the fixed orifice (when flowing) sucks a combination of clean air (from the air cleaner) and crankcase gases. There is no real draw through which seems an odd choice, but maybe this is for a reason. I think it would be better to pull air through through the crankcase by retaining the vent on the oil fill tube, but maybe I'm neglecting something. I'm interested in people's thoughts and experiences related to this.

Thanks! Ken

60BDD63E-E996-4D80-939B-1FCA92C6B9E9 by kenhenry_06268, on Flickr

843BF116-38D0-43E0-B885-CC82D2C7DBE9 by kenhenry_06268, on Flickr

E98983F5-EDFF-401D-ADEF-238D2B9D2612 by kenhenry_06268, on Flickr

Ken Henry, Rochester, NY USA
1965 Corvair Corsa
140 hp, 4 speed

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Re: PCV or fixed orifice
Posted by: cnicol ()
Date: June 27, 2022 09:59AM

What's shown "should" work but I suspect drawing fresh air through the baffle is bringing oil with it. It's also possible the PCV is flowing too much air.

While the notion of fresh air ventilating the crankcase is a good one, it would seem this one needs development. If it were me, I'd just go back to stock and call it a day.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
65 Canadian Monza 4dr 110/PG 40k
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

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Re: PCV or fixed orifice
Posted by: steve c goodman ()
Date: June 27, 2022 10:11AM

Ken the stock vent tube for 64-9 has an orfice of only .062" for the hose from the vent tube to the balance tube. (turbo excepted in this)


as Craig suggests you undoubtedly have too large of a hole pulling from the top cover to the balance tube. Replace with stock vent tube and try that. It doesn't have to be for 4 carb and you can shorten tube to air cleaner if needed but use the outlet to the balance tube as GM intended.

Remove the vent from the oil filler tube too. Not sure why you did that?

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

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Re: PCV or fixed orifice
Posted by: Lane66m ()
Date: June 27, 2022 10:13AM

Get rid of the PCV valve. It has a large hole to draw up oil and vapors. Too much suction being put on the crankcase. Use same size fixed orifice as the LM engines use. I think it is a 0.064 orifice.

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Re: PCV or fixed orifice
Posted by: isucorvair ()
Date: June 27, 2022 10:14AM

On one of my cars...can't remember which, I actually pulled the orifice portion of the vent tube off the pipe, and jammed it into the section of hose, so it was hidden, but still had the right orifice. Worked fine.


Eric P.
DeWitt, iA

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Re: PCV or fixed orifice
Posted by: RobertC ()
Date: June 27, 2022 10:32AM

As others stated, my Corvair mechanic cut apart a stock 65 tube and reformed it to fit Otto Parts 140 air filters - made a connector in the bottom of pass side air cleaner.

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Re: PCV or fixed orifice
Posted by: KenHenry ()
Date: June 27, 2022 10:49AM

Thanks everyone. Steve: the intent of the moving fresh air inlet to the oil fill was so that during cruise conditions, fresh air would enter there, circulate through the crankcase, and exit through the PCV valve on its way to the combustion chambers. I reasoned this would clean up the engine but instead it just left me with oily carbon deposits in the combustion chambers LOL! I'll just go back to stock I guess, should have the remnants of the stock system around here someplace. Ken

Ken Henry, Rochester, NY USA
1965 Corvair Corsa
140 hp, 4 speed

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Re: PCV or fixed orifice
Posted by: vairmech ()
Date: June 27, 2022 04:49PM

OK, you are over thinking the PCV system! And you are trying to reinvent it. The late model system works very well and is very simple.
While you may not want to get the oil vapor on that nice shiny air filter bottom, it doesn't hurt anything.

The way you have it there is a lot of air moving through the crank case. Air movement carries oil particles with it. If you want to keep what you have then you need a REAL air/oil separator similar to what I chronicled here about 3 years ago. An air/oil separator has a specific build to it, not even close to what they call those in the current catalogues.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: PCV or fixed orifice
Posted by: Richard ()
Date: June 27, 2022 07:14PM

Have you tested to see what the system is doing?

I have a tester that I use, but you can place the palm of your hand over the fill tube and check for a small suction at idle.

On another thread where I saw that same picture of your engine, you stated that the PCV valve came from another application. I think you wrote that it was from a Lexis or some other crap car.

The PCV Valve is basically a one way valve. Other applications may not necessarily have the same flow direction, even if it fits your fittings.

With the engine running, pull the Valve out of the crankcase tube and place you thumb over the end. The valve shout snap shut and you should feel a strong vacuum.

Your rubber hoses are probably too small, even for a cross-over tube.
Use the stock cross-over tube and connect the PCV Valve to the stock port.



Edited 2 time(s). Last edit at 06/27/2022 07:20PM by Richard.

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Re: PCV or fixed orifice
Posted by: 63turbo ()
Date: June 27, 2022 08:20PM

I think you ought to try a air/oil separator with your existing system.

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



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Re: PCV or fixed orifice
Posted by: KenHenry ()
Date: June 28, 2022 04:34AM

Ken, I searched but couldn’t find any internal construction details. If you give me a rough idea of what you did I can fabricate something.

Richard, the valve is oriented correctly and pulling plenty of air, plus *some* oil, enough to gunk up the back of the intake valves in a little over 1000 miles. I have not measured flow (and can’t until everything is reassembled), but crankcase fumes don’t back up to the inlet tube unless the valve is removed and the opening blocked. The hose used was 3/8 for parts of the system under vacuum and 5/8 for the inlet tube, like stock

Kevin, is there a separator design you recommend, and do you use a variable (PCV valve) or fixed orifice? I realize it may be different with you running a turbo.

Best, Ken

Ken Henry, Rochester, NY USA
1965 Corvair Corsa
140 hp, 4 speed

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Re: PCV or fixed orifice
Posted by: 63turbo ()
Date: June 28, 2022 05:16AM

The one I use is made by JLT, the intended application for that particular separator is for draw through supercharged engines. For that application, the 3/8 line off of the PCV line is connected to the intake like you have yours. Those separators do a great job of removing oily vapors from the air. Something that works way better than either a one way valve of a fixed orfice, is one that is tuneable... I will find a link to it and post later today. Those kind of valves work awesome with air/oil separators.

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



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Re: PCV or fixed orifice
Posted by: jamesolefjensen ()
Date: June 28, 2022 09:23AM

I use this style of fuel filter without the screen for the PCV restriction.

[olsensvw.net]

I'm running a Holley also so it's plumbed to the base of the carb with fuel line. I use the factory pipe coming out of the shroud. The end that normally hooks into the air cleaner has one of those mini air filters clamped to it. The "T" on the pipe goes to the carb with this (screenless) fuel filter inline. (I'd take a picture but the 500 MB limit is a pain)

It's not perfect. The mini air filter is a constantly wet with oil and I have to regularly whipe down the engine compartment.

James
65 Corsa
SF Bay Area

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Re: PCV or fixed orifice
Posted by: 63turbo ()
Date: June 28, 2022 10:28AM

63turbo Wrote:
-------------------------------------------------------
> The one I use is made by JLT, the intended application for that particular separator is for draw through supercharged engines. For that application, the 3/8 line off of the PCV line is connected to the intake like you have yours. Those separators do a great job of removing oily vapors from the air. Something that works way better than either a one way valve of a fixed orfice, is one that is tuneable... I will find a link to it and post later today. Those kind of valves work awesome with air/oil separators.

Heres the PCV valve I would recommend you get.[mewagner.com]

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



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Re: PCV or fixed orifice
Posted by: KenHenry ()
Date: July 20, 2022 08:23AM

This solution seems to be working well. I extended the stock crankcase vent tube up to a small catch can mounted under my throttle bracket, using 5/8" hose. The vapors are then drawn out of the catch can into the balance tube through a stock-size fixed orifice, which is jammed into the 3/8 hose near the outlet of the catch can. This system has the advantage over stock of creating some air circulation in the crankcase under conditions where there is manifold vacuum. Air is drawn in through the breather tube welded to the oil fill tube. Ken

Ken Henry, Rochester, NY USA
1965 Corvair Corsa
140 hp, 4 speed



Edited 1 time(s). Last edit at 07/20/2022 08:00PM by American Mel.

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