Here I go again....PCV
- Thread starter opzWE4
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The following is a (long) story I told a while back on this issue along with pics of my "trap door breather" ! Comments are welcome.clemsgn said:When I get a chance, I'll post pics and an explanation of what I've done to help aleviate this problem. I can't now cause it's 2AM and I really should be in bed
Talk soon, Clem
I figured I'd write because I've encountered some very strange oil problems myself. My 87 GN was starting to smoke on deceleration every once in a while (a big cloud)!
After a very intensive 9 month struggle and checking virtually every possibile source for this problem, I finally found it !! For some odd reason, the PCV Valve & Crankcase Ventilation System was allowing this to happen. The system seemed to be operating properly but, if I didn't create a vacuum in the crankcase by blocking off the breather opening, this oil problem persisted !! Here are some particulars : I've owned it since new, oil changed every 3,500 miles, great compression within 5 - 8 lbs. between cylinders, leakdown test showed only 5 - 7 % at BDC, new valve seals, no oil leakage from the turbo (only 10,000 miles on new TE-34), new neoprene front timing cover seal, new intake gaskets (just in case oil was entering into an intake port because of a bad gasket - which it wasn't ! ), and all this on my daily driver with 122,000 miles !! It was not really burning that much oil as I was getting about 1,500 mi. to a quart. This is a bit less than it used to get, but I attributed that to the high mileage. I found out that crankcase pressure or vacuum is very critical, at least on my car, and maybe mileage has a lot to do with it? I was told by a very competent engine builder, that you should not have any pressure in the crankcase what so ever during daily driving. (except under boost conditions of course) My problem never occured under power, even while drag racing ! With a vacuum guage connected to the dipstick, and my regular passenger side breather installed, there were no detectible pressure or vacuum changes happening. With that checked out, I thought I would completely block off the breather opening, and try again. This test showed a vacuum of 4 - 6 in. Hg. while cruising, which leveled off down to 0 in. Hg. when I didn't vary the throttle position. This test under boost produced a pressure of up to 5 - 8 lbs. as long as I stayed into it ! This proceeded to force oil out through the rear main seal and the oil pan gasket, which completely coated the undercarriage of the car !! One thing I did notice with these tests, was my oil/smoke problem disappeared as long as I had the crankcase sealed off !! This was the only way I found to eliminate this smoke! I designed a small trap door on my breather so as to seal the opening under vacuum conditions, and to open up (to vent any pressure) while under boost. This was the best solution all around to retain the original driveability. By the way, I now get about
4000 - 5000 miles to the quart, and with the vacuum almost always in the crankcase, I don't have any signs of oil leaks anywhere ! Best of both worlds !
I know this is long, but I have another story for you. My wife drives a 86 Olds Cutlass Salon ( kissin cousin to a 442), and that car was getting around 5000 - 7000 miles to a quart. ( those Olds V-8 engines are great on oil !) All of a sudden she (my wife) complained that the lifters were ticking on her car. I pulled the dipstick to find no oil on it at all ! I filled it up using 3 qts. and then watched it close for a few days. It was using a quart every 20 miles ! I also noticed her PCV valve was rattling, so I replaced it hoping that was the problem. It helped a little bit bringing it to 200 miles per qt. I then tried putting a 1/8 " restrictor in the 3/8 " hose going to the PCV valve thinking the oil was being sucked up through the PCV system. this actually cured the problem and is back to great oil mileage ! ( this car has 130,000 miles on it )
I guess as the miles pile up on these engines in any car, the pressures that are normal in the crankcase slowly change due to wear and blowby creating these very hard to detect problems ! As long as we're learning something when this happens, I guess it's all worth it !
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NHRA Super Gas
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- Nov 18, 2005
bison said:
I think the insights above are spot on. Like you all, I'm fighting the same issue. I just tonight took off the up-pipe and discovered oil on the plenum/powerplate area of the intake.
I have ordered and installed this product to fix it, will keep everyone posted. Likely won't get to it until this weekend.
http://www.psmbuick.com/products_spcvv.asp
I really like clemsgn's setup. I've done some experimentation with a similar setup. Blocking in both breathers and measuring the vacuum I can pull on the crankcase, I was able to pull a 6-7" Hg vacuum at idle. Wish I had gotten a measurement at cruise, that would have been interesting...
Benefits to maintaining a vacuum on the crankcase:
1. Reduced oil leaks. If you've got air trying to get into the engine past the rear main seal, past the oil pan gasket, past the valve cover gasket, etc... because of the big vauum in the crankcase, oil is going to find it a lot harder to get out.
2. Cleaner oil. The nastys that buildup in oil, water and acids and whatnot, will get boiled off a lot easier under a vacuum than they will at atmospheric pressure.
3. Better ring seal under normal operating conditions. Not sure the magnitude of this, maybe little or none, but some of those hardcore guys run vac pumps on their crankcases for a reason. If maintaining a vacuum on the crankcase helps reduce pumping losses and increases ring seal just a little, heck every little bit helps. I wonder if there would be any effect on mileage...
4. Reduced flow through the PCV valve. Yup. Flow is a function of the pressure difference between two points. Say you are idling at 14" Hg and you have open breathers keeping the crankcase at atm pressure (29" Hg). You have a 15" Hg differential pushing air and vapors through the PCV into the intake. Now seal up the crankcase and develop 6" Hg vacuum in there. Now you only have 8" Hg differential pushing vapor flow through the PCV. With half the pressure difference pushing the flow, flow has to drop.
Now, what did I effects did I see when I did that? Not much change in how the car ran overall. I seem to remember a slightly smoother idle, but it wasn't much if any. Could have been wishful thinking. Didn't try and document any changes in mpg, etc. since I wasn't driving the car often enough. Didn't change the amount of oil I trapped in the PCV line, not any better, but not any worse either. It did change my idle BLMs a good bit, so there must have been a significant change in the flow through the PCV.
Only downside was I really blocked things in. I didn't have a way for positive pressure to get out when under boost. Made a few boosted runs, didn't give me any problems, but I didn't measure the crankcase pressure either. Next iteration is to develop a check valve arrangement for the breathers, let pressure escape but do not let any air flow in. Like clemsgn's setup.
That reminds me... open breathers. How often do you guys actually clean 'em? Because they are always sucking air in. I'm not sure I ever cleaned mine. I'd feel bad if I did that with my air filter, and this is really the same thing. Engine is always sucking in through the breathers, and if you start sucking in dirt, it will probably deposit itself in the oil right there in the valve cover and start circulating. So, give them a cleaning once in a while!
John
Benefits to maintaining a vacuum on the crankcase:
1. Reduced oil leaks. If you've got air trying to get into the engine past the rear main seal, past the oil pan gasket, past the valve cover gasket, etc... because of the big vauum in the crankcase, oil is going to find it a lot harder to get out.
2. Cleaner oil. The nastys that buildup in oil, water and acids and whatnot, will get boiled off a lot easier under a vacuum than they will at atmospheric pressure.
3. Better ring seal under normal operating conditions. Not sure the magnitude of this, maybe little or none, but some of those hardcore guys run vac pumps on their crankcases for a reason. If maintaining a vacuum on the crankcase helps reduce pumping losses and increases ring seal just a little, heck every little bit helps. I wonder if there would be any effect on mileage...
4. Reduced flow through the PCV valve. Yup. Flow is a function of the pressure difference between two points. Say you are idling at 14" Hg and you have open breathers keeping the crankcase at atm pressure (29" Hg). You have a 15" Hg differential pushing air and vapors through the PCV into the intake. Now seal up the crankcase and develop 6" Hg vacuum in there. Now you only have 8" Hg differential pushing vapor flow through the PCV. With half the pressure difference pushing the flow, flow has to drop.
Now, what did I effects did I see when I did that? Not much change in how the car ran overall. I seem to remember a slightly smoother idle, but it wasn't much if any. Could have been wishful thinking. Didn't try and document any changes in mpg, etc. since I wasn't driving the car often enough. Didn't change the amount of oil I trapped in the PCV line, not any better, but not any worse either. It did change my idle BLMs a good bit, so there must have been a significant change in the flow through the PCV.
Only downside was I really blocked things in. I didn't have a way for positive pressure to get out when under boost. Made a few boosted runs, didn't give me any problems, but I didn't measure the crankcase pressure either. Next iteration is to develop a check valve arrangement for the breathers, let pressure escape but do not let any air flow in. Like clemsgn's setup.
That reminds me... open breathers. How often do you guys actually clean 'em? Because they are always sucking air in. I'm not sure I ever cleaned mine. I'd feel bad if I did that with my air filter, and this is really the same thing. Engine is always sucking in through the breathers, and if you start sucking in dirt, it will probably deposit itself in the oil right there in the valve cover and start circulating. So, give them a cleaning once in a while!
John
salvageV6
Daily Driver
- Joined
- May 25, 2001
On my daily drivers you have to clean those breathers once or twice a year due to oily dirt buildup.
That's at 25psi. boost on pump and alky. on a couple of old stock motors.
Also you need to make sure the rubber inside them (if any) is drilled out as large as you can for maximum flow. You'd be surprised at how big the breathers are compared to the cheesy hole they put in some of them.
I usually do it every other time I clean the air filter that hangs under the front bumper in my open Kenne Bell air dam.
So far so good with the catch can from Ebay and stock PCV and a check valve from US Plastics.
That's at 25psi. boost on pump and alky. on a couple of old stock motors.
Also you need to make sure the rubber inside them (if any) is drilled out as large as you can for maximum flow. You'd be surprised at how big the breathers are compared to the cheesy hole they put in some of them.
I usually do it every other time I clean the air filter that hangs under the front bumper in my open Kenne Bell air dam.
So far so good with the catch can from Ebay and stock PCV and a check valve from US Plastics.
- Joined
- Feb 18, 2006
clemsgn said:
This is a great idea.
Is that trap door spring loaded?
Rick87GN said:
No, it has stops on the hinge so it doesn't open too far. When under vacuum it just closes under it's own weight.
(Turbo2nr) thanks for your comments...I don't think they came with exhaust valve seals from the factory, but I have some on the M & A heads on my Turbo T now. Only problem is the small white plastic ring that the valve goes through, keeps popping out of the rubber seal itself and then it's obviously not as effective. I have a better type of seal on the intakes, but even they slide off the guide and ride up and down with the valve. I just removed them and compressed the metal ring smaller so they would grip the guide better. Time will tell ??
Thanks again for the comments
I'm not the smartest guy, but I saw a little something about reaming out the seals just a bit. I saw a section on it in a Stage motor book. Lets just enough oil thru to lube the valve, but won't do like you're talking'bout.
It was the red covered booklet, only around 30pages in this book. Sorry, forgot the name.
It was the red covered booklet, only around 30pages in this book. Sorry, forgot the name.
Just for a few tests i will be datalogging my pcv pressure and inlet pipe pressures via my lm-1. So we will see what pressures we get in the system when its plugged or open. But this will be happening in a few weeks until its all ready, so look forward to some data
- Joined
- Feb 18, 2006
I have been pondering the idea of check valving the breathers in the valve cover so that they will let air out but not in. Seems logical to me.
I just worrie about too much negative preasure in the case messing with the oil flow. How much is too much?
Which leads me to something else that would need to be in conjunction. Some type of blow off or regulator that would only let negative preasure build to say 15in.
I know our cars ecm does not like any air that does not come through the maf. This would also help that problem.
I think this would cure the oil sucking also.
Rick
I just worrie about too much negative preasure in the case messing with the oil flow. How much is too much?
Which leads me to something else that would need to be in conjunction. Some type of blow off or regulator that would only let negative preasure build to say 15in.
I know our cars ecm does not like any air that does not come through the maf. This would also help that problem.
I think this would cure the oil sucking also.
Rick
Rick, as others have mentioned, vacuum in the crankcase has many plusses and normally runs from 5-8 in HG. It helps the rings seal, almost completely eliminates leaks, helps draw the drain oil from the turbo and keeps the crankcase cleaner with virtually no moisture buildup etc. etc. Stock rope type front and rear main seals dont work as well, cause they allow too much air in (leak) so a vacuum doesn't build up as easily. The only thing is, you need a way for the excess crankcase pressure to get out under boost. I found that modifying a stock type breather with a trap door works well, but I now may need another one on the other valve cover to work with my setup during race conditions....PT68 and 30 psi. (see pics of breather in my post above) If anyone comes up with a better check valve (large) let us know.Rick87GN said:
Hope that helps, Clem
Smoke again
I now seem to have a problem again with my current ride (87 Turbo T) The longer it runs, it smokes blue at idle and sometimes at cruise. Leakdown is good at 4 % in all cylinders and I have my "trap door" breather on drivers valve cover. Funny thing is, all 3 spark plugs on pass side are a bit wet looking and oil on threads, but the drivers side were quite dry in comparison. These are M&A heads. The valve covers are definately not leaking down to the plugs. After valve cover removal, I noticed 4 of 6 valve seals on both sides had come off the guide and were going up and down with the valve. Funny thing was 2 were intakes and 2 exhaust on each side, so why are the plugs somewhat wet on the pass side only ? Anyone else experience this B-4 ? I removed the seals (they're new w/less than 500 miles) and compressed the metal ring tighter that holds them to the guide, and reinstalled them again...hopefully they will stay put ! This may have been my "blue smoke problem, but I still don't know why just the pass side plugs were a bit wet ? Anyone have any ideas ? I suspect the turbo could be a source of the smoke also, so I will eliminate it as a possibility if the valve seals don't do the trick.
Thanks for any comments ! Clem
I now seem to have a problem again with my current ride (87 Turbo T) The longer it runs, it smokes blue at idle and sometimes at cruise. Leakdown is good at 4 % in all cylinders and I have my "trap door" breather on drivers valve cover. Funny thing is, all 3 spark plugs on pass side are a bit wet looking and oil on threads, but the drivers side were quite dry in comparison. These are M&A heads. The valve covers are definately not leaking down to the plugs. After valve cover removal, I noticed 4 of 6 valve seals on both sides had come off the guide and were going up and down with the valve. Funny thing was 2 were intakes and 2 exhaust on each side, so why are the plugs somewhat wet on the pass side only ? Anyone else experience this B-4 ? I removed the seals (they're new w/less than 500 miles) and compressed the metal ring tighter that holds them to the guide, and reinstalled them again...hopefully they will stay put ! This may have been my "blue smoke problem, but I still don't know why just the pass side plugs were a bit wet ? Anyone have any ideas ? I suspect the turbo could be a source of the smoke also, so I will eliminate it as a possibility if the valve seals don't do the trick.
Thanks for any comments ! Clem
- Joined
- Feb 18, 2006
Thanks clemsgn,
I am in the process of developing a system.
It's basicly the same concept that you are using. I want to check valve the breathers and also run a vacuum blow off.
I can't belive no one has a system to do this.
Guess I will just have to make one. I 'll keep you posted.
I am in the process of developing a system.
It's basicly the same concept that you are using. I want to check valve the breathers and also run a vacuum blow off.
I can't belive no one has a system to do this.
Guess I will just have to make one. I 'll keep you posted.
For now i have moved the pcv valve to the valve cover and have it raised up in the factory oil filler, so its not in the stream of the oil. I found a -12 AN check valve from a surplus store locally, and it fits perfect in the breather hole on the other valve cover. Now i just need a catch can to attach to the 12 an fitting . DO you think a single -12 an fitting is enough flow or do i need to put another check valve in?
- Joined
- Feb 18, 2006
I think your best bet would be to run a seperate vacuum gauge of the dipstick tube and whatch the gauge.
I dont think you ever want to see positive preasure on the crank case. If you do then that check valve is not good enough.
Be carefull. Too much preasure in the case and something is going to blow.
I dont think you ever want to see positive preasure on the crank case. If you do then that check valve is not good enough.
Be carefull. Too much preasure in the case and something is going to blow.
