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| So has anyone actually fixed the oil puking out of the PCV?; Tons of posts on what it could be, no posts about the actual result? | |
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| Tweet Topic Started: Dec 29 2011, 10:27 AM (4,276 Views) | |
| merlot566jka | Dec 30 2011, 09:37 AM Post #16 |
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Engineer
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Ive read your responses. I have read other information on other forums as well. I respect your opinions. A few clarifications first... I just bought this car and have maybe 1200m on it total. I do take care of my vehicles, which is why I am doing this work. The rings are not totally seated yet... This is controversial to many, some say its broke in in 15mins of driving, others say it takes about 1000 miles... others say.... bla bla bla. The fact is I have blow by that doesn’t smell like fuel, and there isn’t any burning oil in the chamber. I have new rings. The bottle bore brush does mask if there were any out of round issues. And perhaps that may be the issue. I checked the compression cold and immediately after the ring install, before any break in. I will recheck tonight or tomorrow. I have the large hole gasket that came in the mail last night. I should get it on tonight or tomorrow. I have found tons of posts on this issue, from the turbo engines to the run of the mill g10. it seems lots of people have this issue. And most have it after a re-ring or excessive miles. It leads me to a few thoughts... People who have the issue after a re-ring see a good result after using the large hole or modified head gasket. It may be that after they have driven the car for some time and change the head gasket and see a resolution, it may be that they waited long enough for the rings to seat, and the head gasket doesn’t actually do that much. Or not, and the head gasket is really a fix. People who have worn rings and change over to the modified gasket...well I haven’t seen that just yet, but it would be interesting to see if that does the same thing. But let’s go over that head gasket thing for a min... I will think out loud here. The oil return holes are on the front side of the engine. There are four of them and they are fairly large. This should be more than adequate to drain back the oil from the head. On the back side of the block, we have the other two holes. in the stock style gasket, we have one hole that is misaligned, and another that is small in proportion to the hole on the head and block. These holes are for crank case gases. The engine is angled so that the front oil return holes are lower than the crank case gas holes. Which makes sense, flowing oil will roll down these holes. Crank case gases have further to travel into the head and likely the oil will drop out of suspension once the gases have reached the holes. This prevents oil laden gases to be pushed into the head. So what is going on now, that wasn’t going on originally? Let’s assume we have blow by (obviously we must). If the extra pressure in the crank case cannot make its way past the small and misaligned holes, then it is forced to go through the larger holes in the front of the engine. These holes are where the oil is supposed to be draining back. If you have ever tried to use a water hose in the wind, you know you’re going to get wet! This is happening in the drain holes, the air is forcing the oil into a tornado of sorts, and it’s not draining back properly. Instantly you have more oil in the head and its being suspended in the air. The gasses are forced to leave the crank case breather (valve cover vent) and they are carrying lots of oil now. This is where the oil comes from. Now when we use the larger holed head gasket, the crank case gases stop being forced against the draining oil, and the gas is no longer pressurized as much because it has an easier path to the head. There is now less oil in the gases, and less pressure, so of course, we have solved the issue. But not really... But why didn’t it do it originally, I wonder. Well that’s because there wasn’t as much blow by. Duh. While honing the block and adding new rings should, in theory, restore compression, I don’t think it is doing it as we (or maybe just 'I') assume. A true bore and hone with oversized pistons and rings is needed. Without knowing the RA (or whatever you want to use to measure hardness) of the liners, we don't really know how much we are actually taking off by honing. And we don't know how much we are wearing down the cyl with these new harder rings. (Assuming we don’t have the precision instruments to measure this) So when we re-ring the engine, we are just de-glazing adding new rings… and of course it is better than worn rings. But what we still have is blow by. Because... the forces on the liner isn’t lateral at all... we have side to side forces (respective to piston rotation on the rod and pin) and this is different at the top, bottom and middle of the stroke. So we have an irregular shaped hole in different spots. New rings and a hone won’t fix an out of round cylinder. Using a flat honing stone (not bottle brush) will wear down the high points and make the bore more "square"… but all we are doing is making the hole as big as the most worn spot... which really doesn’t do much for new rings, as this just increases ring gap. We in-turn, still have blow by, just not as much as before. When the engine performs better than it did before, and our mileage is restored, we wonder "WTF its got new rings and everything, compression is good, why am I burning oil/blowing oil out" And that makes me think about "rings being seated" it may take longer on a honed engine, BECAUSE THE RINGS HAVE TO WEAR TO AN IRREGULAR SHAPPED HOLE. Uh, duh? This is just thinking out loud here. I may just get another short block and drop it off at the machine shop. As I have come to the conclusion that honing is almost worthless when the engine is worn this much.
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| bogs | Dec 30 2011, 10:03 AM Post #17 |
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Duct tape heals all wounds
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I don't actually see anything wrong with the theory you laid out, testing it would be pretty tough to do though
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| merlot566jka | Dec 30 2011, 11:07 PM Post #18 |
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Engineer
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Anyone? |
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| redpepe | Dec 31 2011, 06:51 AM Post #19 |
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good discussion. thx. when my engine was wearing out at 325K it had the 'original' small hole head gasket and never blew any smoke. the rings and any accumulated wear did not seem to be the problem in my case. after the rebuild which was done by a very competent shop / builder [including bore / pistons] it did consistently blow nasty clouds at anything over 60mph. i tried waiting for the rings to seat and maybe didn't wait long enough [over 1000 mi. i think] but the new [modified by me] gasket did the trick and has had no problem since .. approaching 360k. as a reality check, my equally baffled builder ordered 4 new gaskets from different suppliers and they all had small holes. incidentally i tried a few things while waiting for the seating of the rings including very conscientiously driving half a tank on a freeway all at 50-60mph and achieved 86mpg. i also drove with a friend in the passenger seat holding a temp 'catch can' connected to the pcv port with a long clear plastic hose so we could monitor the specifics of the oil coming from the engine while driving / under load. my new rebuild never achieved the highest compression specified but was more than adequate at 170's if i remember correctly .... and i haven't done a compression check since but i'm getting curious. |
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| clarkdw | Dec 31 2011, 11:14 AM Post #20 |
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I have had a fair amount of experience trying to cure this problem on large overbore Mini race engines and will offer a couple of points. First is exactly as Merlot surmised. Honing an out of round, cone shaped, or name your other distortion cylinder is pretty much a wasted exercise. The cylinders in the G10 are pretty stout and probably do not get the same bore flex we were getting in the Mini with large overbore so we can discount that as a problem but if the cylinder is not straight and round no amount of honing is going to fix it. I needs to be bored true. Second thing and the fix that finally allowed us to get good sealing on the Mini is the use of a cast top ring rather than Moly. The Moly ring in the top groove is extremely long wearing and is not forgiving of out of round cylinders. It takes a VERY long time to break in if the cylinder is out of round or otherwise misshapen if it ever breaks in at all. Moly rings need the cylinder to be round, straight and with a fine finish. On the Honda race Kart engines I built the cylinders were bored very straight and round and honed with 400 stones. There was NO break in. The Moly top ring sealed up immediately and within a couple of minutes would show virtually no leakdown %. I think a very interesting experiment would be to do the common type of rebuild most do on the G10 and use a soft iron top ring instead of the Moly. I suspect with a good finish on the bore it would prove to be more satisfactory than the Moly in the case of older bores. If a rebore is done and new pistons used the opportunity is there to get the cylinder true so the Moly ring would be better in that case. Side-note: In the case of the large overbore Mini engines with lots of bore flex we used iron top rings and still had some problems albeit less. The final cure there was to connect the sump to the valve cover to balance the pressure using two 1" hoses. Not the right answer but it got the job done. |
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| GeoPete | Dec 31 2011, 06:22 PM Post #21 |
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AAS Auto Technology past ASE Master Tech
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I had to install a catch can because my y tube was shot. Could not find a replacement, even at a Chevy dealer. Anyone know who carries them? |
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| merlot566jka | Dec 31 2011, 11:29 PM Post #22 |
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Engineer
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Well I pulled the head today. NO OIL RESTRICTOR!!! So my brother and I made one. Pics to follow. Used the large hole gasket. Re-honed with stones (not dingle berries) Measured with telescoping bore gauges. 73.94mm on top 74.11mm in the middle 73.99 on bottom. Solid stone hone showed this barrel shape. Result? No more blowby. Will write more later |
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| clarkdw | Jan 1 2012, 08:48 AM Post #23 |
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0.17mm barrel? That is 0.0067" and will never give you a long living or decent seal on the rings. Time for a rebore and new pistons as soon as you can afford it. That is way too much difference to hone out and has, for sure, put your piston clearance way over the top. On the positive side, finding the restrictor missing will probably allow you to run with minimal oiling problems till you can organize for a rebuild. What size did you make the restrictor? I don't know what size the factory one was but you need to be careful not to go too small. Happy New Year
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| clarkdw | Jan 1 2012, 09:32 AM Post #24 |
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Some hose and one of these Break off Tee is a possibility. It allows for the different size hoses on the y. We can get them at Canadian Tire. I imagine some auto parts suppliers carry them or ebay. Just cut off the T to the appropriate size. |
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| t3ragtop | Jan 1 2012, 10:56 AM Post #25 |
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Turbo3 and Twincam Tweaker
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while not a cure all for the problem, the late model valve cover (92-up) has a very much improved oil vapor separator over the older, square looking valve cover. i routinely swap the older style valve cover to the newer style and that helps out with the more minor oil fouling of the air filter. |
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| merlot566jka | Jan 1 2012, 10:59 AM Post #26 |
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Engineer
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I totally agree. I can afford it, the real question is, do I want to go through with it.. The restrictor is M6x1.0 and the hole is 1/16. I figure that was about as small as I could go. I do not have a factory one for comparison. I would like to get another engine to build while I drive this one and work on the rest of the car. My other two vehicles are not daily drivers, The corvette doesnt do winter and the Duece doesnt do MPG. So it looks like this is going to be a temporary engine. Happy new year!!
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| bbowens | Aug 13 2013, 05:55 PM Post #27 |
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is there a way to verify if the oil check valve is there without pulling the head? I'm having this oil problem, but my compression is good (210 across the board, last check)?
Edited by bbowens, Aug 13 2013, 06:43 PM.
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| geostang | Aug 13 2013, 08:39 PM Post #28 |
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If you dont disconnect the fuel injector power prior to compression testing you will get 150 everytime on a good 200 engine, fuel washes the oil off the cyls. My 92 doesnt have this issue, although it has smoked two times. Both times I had pulled into a place from the highway, and it sat for ten minutes, then when I left, it left a smoke trail, and both times it was 1/2 a quart low. No idea why but those are the facts ![]() I have new PCV on this xfi. |
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| geostang | Aug 13 2013, 08:42 PM Post #29 |
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And for what its worth |
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| geostang | Aug 13 2013, 09:07 PM Post #30 |
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And his newest fart fix |
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