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PCV and oil leaks
- Thread starter mgtf328
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Steve,
Sorry, I've probably missed something. Where's the PCV located on the image above? I can't see it.
Is that 5" or 0.5" under hard acceleration? I think 5" may be a bit on the high side. If it is 5" I would say the valve isn't reaching the "sonic flow" condition because the valve orifice is a bit on the large side. It would be interesting to try a smaller valve rather than a larger one.
I'm proposing to use a manometer instead of a gauge because all of the gauges I've seen here measure 0 - 30" Hg. I don't expect cheap gauges to be accurate enough to measure 1" Hg reliably. Anyway why spend 30 bucks when I can make a manometer out of a bit of plastic tubing!
On another point, I'm not claiming this is rocket science. When you search the web you find MANY technical papers on this subject by University's, Ford, Caterpillar, Toyota, etc. and you start to wonder why so much money has been spent on it. From my reading of the few I have downloaded, drawing a vacuum on the crankcase will affect oil distribution and engine performance. I guess the manufacturer's are trying to avoid warranty claims by funding this research!
Most papers I've seen agree that the depression isn't arbitrary. They're trying to avoid sucking oil/air/dirt through engine seals or cavitation/slip in the pump.
To conclude, I agree, apart from the fact that it interests old retired engineers with little else to do (Me!) most of us are probably trying this to prevent oil leaks. After all it's cheaper than pulling the engine out. As you get older you have to work smarter, that engine is heavy!
AJ
ps I wouldn't dream of leave my Porsche idling with the oil cap off. Why would you do this?
Sorry, I've probably missed something. Where's the PCV located on the image above? I can't see it.
Is that 5" or 0.5" under hard acceleration? I think 5" may be a bit on the high side. If it is 5" I would say the valve isn't reaching the "sonic flow" condition because the valve orifice is a bit on the large side. It would be interesting to try a smaller valve rather than a larger one.
I'm proposing to use a manometer instead of a gauge because all of the gauges I've seen here measure 0 - 30" Hg. I don't expect cheap gauges to be accurate enough to measure 1" Hg reliably. Anyway why spend 30 bucks when I can make a manometer out of a bit of plastic tubing!
On another point, I'm not claiming this is rocket science. When you search the web you find MANY technical papers on this subject by University's, Ford, Caterpillar, Toyota, etc. and you start to wonder why so much money has been spent on it. From my reading of the few I have downloaded, drawing a vacuum on the crankcase will affect oil distribution and engine performance. I guess the manufacturer's are trying to avoid warranty claims by funding this research!
Most papers I've seen agree that the depression isn't arbitrary. They're trying to avoid sucking oil/air/dirt through engine seals or cavitation/slip in the pump.
To conclude, I agree, apart from the fact that it interests old retired engineers with little else to do (Me!) most of us are probably trying this to prevent oil leaks. After all it's cheaper than pulling the engine out. As you get older you have to work smarter, that engine is heavy!
AJ
ps I wouldn't dream of leave my Porsche idling with the oil cap off. Why would you do this?
D
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steve
are you thinking you will not need an oil catch can in the line?
once it cools down, i will have to test my set up on the road and see if my reading changes.
only other thing i did was put a small mark on my valve. just a quick check to see if it moved while driving.
are you thinking you will not need an oil catch can in the line?
once it cools down, i will have to test my set up on the road and see if my reading changes.
only other thing i did was put a small mark on my valve. just a quick check to see if it moved while driving.
D
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AJ
if you look close i think Steve has his filter and air valve hooked to his side pipe, which is in front of his Valve cover T. his valve cover T has his connection for his gauge on the laft side and his PCV valve on the right side which goes to his manifold.
if you look close i think Steve has his filter and air valve hooked to his side pipe, which is in front of his Valve cover T. his valve cover T has his connection for his gauge on the laft side and his PCV valve on the right side which goes to his manifold.
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AJ - apologies for the unclear photo; my PCV valve is per the pic in Post #5 above. Yes, it's 0.5" under hard acceleration.
DD - later today, I'll be working on making an orofice to match the flow on the brass valve. My valve is fairly stiff, so I wouldn't be worrying about it shifting while driving.
DD - later today, I'll be working on making an orofice to match the flow on the brass valve. My valve is fairly stiff, so I wouldn't be worrying about it shifting while driving.
Congratulations Steve, I think you've cracked it.
How will you size the orifice to match the valve flow, trial and error? When I did my MG I used a short length of steel rod with a 1.7mm hole drilled through it and I rammed it into the pipe before the PCV
I tried fitting a catch tank between my breather T and air filter and it pressurised the rocker box and the gasket leaked. See image attached. I think the sintered metal filter in the head is too fine and there wasn't enough suction to draw the gases through from the crankcase. It may work better attached to the inlet manifold.
If you could summarise what you did when you finish I think we can draw a thick line under this post and PCV valves.
If I order one of those valves from NAPA tomorrow, do you think I might get by next spring!!
Thanks guys.
AJ
How will you size the orifice to match the valve flow, trial and error? When I did my MG I used a short length of steel rod with a 1.7mm hole drilled through it and I rammed it into the pipe before the PCV
I tried fitting a catch tank between my breather T and air filter and it pressurised the rocker box and the gasket leaked. See image attached. I think the sintered metal filter in the head is too fine and there wasn't enough suction to draw the gases through from the crankcase. It may work better attached to the inlet manifold.
If you could summarise what you did when you finish I think we can draw a thick line under this post and PCV valves.
If I order one of those valves from NAPA tomorrow, do you think I might get by next spring!!
Thanks guys.
AJ
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AJ - I've never felt the need for a catch tank. My engine has <7000 miles since the rebuild. Very little oil seen in the PCV valve after running. Will keep checking.
Am using a 1/2" electrical panel hole plug. For the jet, 7/64" hole resulted in almost no vacuum. Settled on 3/32" hogged out slightly to give: 1.5" Hg idle or downhill; 1" cruise; 0.5" hard acceleration.
I'm going to trim the edges and enclose it in the 5/8" hose from the side pipe to the rear air cleaner.
DD - what did you use to plug the left side of the T?
Am using a 1/2" electrical panel hole plug. For the jet, 7/64" hole resulted in almost no vacuum. Settled on 3/32" hogged out slightly to give: 1.5" Hg idle or downhill; 1" cruise; 0.5" hard acceleration.
I'm going to trim the edges and enclose it in the 5/8" hose from the side pipe to the rear air cleaner.
DD - what did you use to plug the left side of the T?
D
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steve
i got rubber stoppers from Lowes. they were in one of the drawers in the bolt aisle.
i got rubber stoppers from Lowes. they were in one of the drawers in the bolt aisle.
D
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Steve
much cleaner set up.
you were asking about the plug i used. you could just put a rubber cap over your fitting to seal that side off. then it would be easy to hookup the gauge anytime.
same idea as here just up on top.
much cleaner set up.
you were asking about the plug i used. you could just put a rubber cap over your fitting to seal that side off. then it would be easy to hookup the gauge anytime.
same idea as here just up on top.
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Good idea about the cap. I need to replace my lo-rent plastic barb with a cool brass barb like yours.
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Bob_Spidell
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I put something like that in the hole in the bell housing for the release bearing fork. I think it's there for installing/extracting the tapered pin on the fork, but figured it would allow dust into the bell housing on a dirt road. I wasn't sure of the size when I was in Lowe's, so now I have a collection of them