wheelman Posted May 16, 2007 Share Posted May 16, 2007 My wife video tapes my auto-x runs for me so I can review them and try to improve my line. At the last event the course was setup with a relatively long stretch where I topped out 2nd gear. I have the rev limiter on the LT1 set to 6300rpm and know I hit it. When I reviewed the video I noticed a small puff of oil smoke at the end of that stretch. I'm thinking this is just the valve covers have filled with oil and a small amount is pulled into the intake through the PCV valve. Does this make sense or should I be looking for problems in other places? Wheelman Quote Link to comment Share on other sites More sharing options...
wheelman Posted May 18, 2007 Author Share Posted May 18, 2007 Ok, nobody seems to have any insight into this. Anyway I did some more research on my own, went out and removed the "PCV Valve" and hose that runs to the intake and found no valve at all. There's an elbow fitting that plugs into a rubber grommet in the valve cover and the hose running to the intake. Unless the PCV valve is inside the valve cover (I don't remember seeing one) or the intake (would be very difficult to replace) there isn't one. When I removed the hose running to the intake it had drops of oil in it so I'm thinking my idea about the puffs of smoke at the end of the straight stretch are correct. I'm pretty sure now that the valve cover was relatively full of oil by the end of the straight and when I lifted on the throttle the additional vacuum in the intake pulled some oil in and subsequently burned it, hence the puff of blue oil smoke. If anybody has any alternate theories please voice them, I'm open to exploring other causes for the oil smoke. Wheelman Quote Link to comment Share on other sites More sharing options...
deja Posted May 18, 2007 Share Posted May 18, 2007 Ok, nobody seems to have any insight into this. Anyway I did some more research on my own, went out and removed the "PCV Valve" and hose that runs to the intake and found no valve at all. There's an elbow fitting that plugs into a rubber grommet in the valve cover and the hose running to the intake. Unless the PCV valve is inside the valve cover (I don't remember seeing one) or the intake (would be very difficult to replace) there isn't one. When I removed the hose running to the intake it had drops of oil in it so I'm thinking my idea about the puffs of smoke at the end of the straight stretch are correct. I'm pretty sure now that the valve cover was relatively full of oil by the end of the straight and when I lifted on the throttle the additional vacuum in the intake pulled some oil in and subsequently burned it, hence the puff of blue oil smoke. If anybody has any alternate theories please voice them, I'm open to exploring other causes for the oil smoke. Wheelman According to shbox.com this is where the pcv valve is. Quote Link to comment Share on other sites More sharing options...
HICKL Posted May 18, 2007 Share Posted May 18, 2007 Wheelman, I have experienced the same puff of smoke on my old school 350 when running valve covers with no baffles inside. I don't know if this is relevant to your situation or not. Jeff Quote Link to comment Share on other sites More sharing options...
wheelman Posted May 18, 2007 Author Share Posted May 18, 2007 OK Deja now I feel really stupid!! I checked out the "other" side of the intake while I was home for lunch today and found the PCV right where your picture shows it. I got so fixated on the hose that connects to the valve cover on the right hand side of the engine I didn't even look at the other side, even though I've seen it a thousand times. Anyway the hose from the valve cover connects to the throttle body and the metal tube the PCV connects to also connects to the throttle body. So the PCV system runs though the throttle body. I pulled the PCV valve, it's working fine, and found more oil which reinforces my thoery that the oil smoke comes from oil being pulled/pushed through the PCV valve into the intake. I'm going to do some more research on exactly how this system works so I understand it and either validate or refute my theory. Wheelman Quote Link to comment Share on other sites More sharing options...
wheelman Posted May 18, 2007 Author Share Posted May 18, 2007 Ok, here's the scoop on how the PCV system works on an LT1. First, the hose connected to the valve cover does not pull air from inside the crankcase but provides a filtered air source for air to go into the crankcase. It connects to the throttle body and allows air that has passed through the MAF and the air filter to be pulled into the crankcase. Second, the PCV plugs into a grommet on the left side of the intake manifold which connects to passages in the manifold that access the lifter valley. Third, a hose connects the PCV valve to another port on the throttle body that's behind the throttle plates so it has a vacuum on it when the engine is running. So the PCV system pulls air from the lifter valley into the intake causing a slight vacuum inside the engine block and valve covers. This vacuum evacuates vapors from the crankcase. The vent on the passenger side valve cover allows filtered and measured air into the crankcase preventing to much vacuum from building up. It's possible for positive pressure to build up in the crankcase if the PCV is plugged or there's more blow-by than it can vent. This would cause vapor and/or oil to be pushed through the valve cover vent into the intake in front of the throttle plates. After all this I'm pretty sure the puff of oil smoke I saw came from the PCV system but I'm not sure if the oil went through the PCV valve or the vent tube, both had oil in them when I checked and the engine has 102,000 miles on it. Anyway I'm thinking of putting a catch can on the PCV line to at least eliminate that route. If I still see the smoke I might put a catch can on the vent as well. Hope this info helps some others understand this system, it seems everytime I turn around I find something just a little different about these LT1 engines. Wheelman Quote Link to comment Share on other sites More sharing options...
deja Posted May 19, 2007 Share Posted May 19, 2007 Ok, here's the scoop on how the PCV system works on an LT1. First, the hose connected to the valve cover does not pull air from inside the crankcase but provides a filtered air source for air to go into the crankcase. It connects to the throttle body and allows air that has passed through the MAF and the air filter to be pulled into the crankcase. Second, the PCV plugs into a grommet on the left side of the intake manifold which connects to passages in the manifold that access the lifter valley. Third, a hose connects the PCV valve to another port on the throttle body that's behind the throttle plates so it has a vacuum on it when the engine is running. So the PCV system pulls air from the lifter valley into the intake causing a slight vacuum inside the engine block and valve covers. This vacuum evacuates vapors from the crankcase. The vent on the passenger side valve cover allows filtered and measured air into the crankcase preventing to much vacuum from building up. It's possible for positive pressure to build up in the crankcase if the PCV is plugged or there's more blow-by than it can vent. This would cause vapor and/or oil to be pushed through the valve cover vent into the intake in front of the throttle plates. After all this I'm pretty sure the puff of oil smoke I saw came from the PCV system but I'm not sure if the oil went through the PCV valve or the vent tube, both had oil in them when I checked and the engine has 102,000 miles on it. Anyway I'm thinking of putting a catch can on the PCV line to at least eliminate that route. If I still see the smoke I might put a catch can on the vent as well. Hope this info helps some others understand this system, it seems everytime I turn around I find something just a little different about these LT1 engines. Wheelman Interesting. When I replaced the hose that goes to the valve cover the old one had some oil in it. I have about the same milage on my engine, the oil might be normal. Quote Link to comment Share on other sites More sharing options...
wheelman Posted May 19, 2007 Author Share Posted May 19, 2007 Yeah I think it's normal but I want to get rid of that puff of smoke after a high rpm run. I also looked in my intake manifold tonight through the throttle body and it's lined with carbon deposits. I think a catch can will help to stop more of that forming and may even help get rid of what's already there. Wheelman Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 21, 2007 Share Posted May 21, 2007 I'd love to see what you come up with for a catch can. I need on my Z and my Galant VR-4. Something small would be cool, and something that drains back to the pan would also be nice. I know, I'd need to provide a path for that back into the pan. Quote Link to comment Share on other sites More sharing options...
wheelman Posted May 21, 2007 Author Share Posted May 21, 2007 I'll take a picture of it. Are you sure you want to drain it back to the pan? From what I've read the oil collected by these things is pretty contaminated with water and fuel. Wheelman Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 21, 2007 Share Posted May 21, 2007 Good point on the drain back issue. I guess I should just not be lazy and be happy with a quick and easy way to drain it into something, and maybe a sight tube on the side of it? Quote Link to comment Share on other sites More sharing options...
wheelman Posted May 21, 2007 Author Share Posted May 21, 2007 It'll be this coming weekend before I can post any pictures, my wife has my camera and she's visiting friends back east right now. She gets home on Thursday so I might be able to have some pictures up by Friday night. I used 2" PVC pipe, some brass fittings I had lying around from my fuel system and a drain from a coolant catch bottle. Cost me about 12 dollars. I'm going to redo it though. I originally built it with the inlet on the top and the exit on the side, but now that I think about it it would be better to have both on the top. I also used a short length of tubing soldered to the inlet fitting to increase the distance between the inlet and outlet inside the can. That way the oil would have a more difficult angle to turn in order to be sucked into the exit. Moving the exit to the top will make the angle even more extreme plus reduce the chance of oil being pulled into it during hard cornering or braking. Does that make any sense??? Wheelman Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 21, 2007 Share Posted May 21, 2007 You guys will be missing out on the benefit of having vacuum in the crankcase if you just route it to a catch can. Not that this is a horrible idea, I had my L6 running like that for years. My current plan is to do the exhaust PCV setup to get the vacuum without putting a bunch of oily garbage into the intake. You can also use a vacuum pump from a diesel and hook that into your catch can. The supposed benefits of the vacuum are better seal on the piston rings, not burning oily crap anymore, and even less wind resistance in the crankcase. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted May 21, 2007 Share Posted May 21, 2007 You route the PCV through a catch can and into the intake. The catch can is just an oil separator. Here is a popular version from LS1tech.com. It has an internal filter to catch the oil mist http://www.ls1tech.com/forums/showthread.php?t=589855&page=1&pp=20 And here is the $40 Arkansas special http://www.ls1tech.com/forums/showthread.php?t=563211 Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 21, 2007 Share Posted May 21, 2007 Oh. Well you're still burning whatever crap comes out of the crankcase, although that may or may not be enough of an issue to consider something else... Quote Link to comment Share on other sites More sharing options...
Hey_Allen Posted May 25, 2007 Share Posted May 25, 2007 A number of factory turbo cars come with a seperator of some sort fitted. The idea being to seperate the oil from the airflow. Often they have some sort of return to the crankcase or oil pan to drain back down. I know my old Mercedes diesel has a spring loaded valve at the top of the oil pan where the seperator drains to. On an Isuzu turbo I had long ago, it had a set of baffles in a little box on top of the valve cover, again with a drain back to the oil pan. When they work properly, they seem to cut down on the oil burning, and reduce HC in exhaust to some extent. Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 26, 2007 Share Posted May 26, 2007 The $40 Arkansas special looks like the catch can I saw talked about on a DSM forum, which pointed to the Z06Vette.com forum: (See post #90 below) http://www.dsmtalk.com/forums/showthread.php?t=177223&page=4 http://www.z06vette.com/forums/printthread.php?t=73303 I'm about to put two of these on my Galant VR-4. It's just an air compressor oil/air separator/filter. For boost applications, "oldman" on the DSM forum suggests a check valve that follows the PCV valve. Quote Link to comment Share on other sites More sharing options...
wheelman Posted May 30, 2007 Author Share Posted May 30, 2007 Here is the picture of mine I said I'd post, sorry it took so long. Wheelman Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted May 30, 2007 Share Posted May 30, 2007 If the pcv system is your smoke source, why does it wait for the end of the straight? (It's in play all the time). Could be, when you lift, the high vacuum sucks a little oil past the 102K intake valve seals. <> Quote Link to comment Share on other sites More sharing options...
wheelman Posted May 30, 2007 Author Share Posted May 30, 2007 A.G., Thats true. My thought was that the high rpms pumped more oil into the valve covers and lifter valley and when I lifted the high vacuum pulled oil in through the PCV but it could be the seals. The next Auto-X event I'll have the wife video tape a couple runs so I'll be able to tell if my catch can helped. If it didn't then I guess it's time for new seals, but I'll wait for a rebuild to replace those. Wheelman Quote Link to comment Share on other sites More sharing options...
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