Boog Posted November 30, 2014 Share Posted November 30, 2014 (edited) Hello fellow members, My current setup (stock) has been burning oil, but only on backpressure. I'll be going down a hill, engine braking, and my car will spew blue smoke. From the blue and the smell, I definitely know it's oil. I also had a "Stage 3" head put on a year or so ago, before I started doing my own work, and I know there is no problem from that. I am thinking that it is piston rings due to my symptoms sounding like blow by. With that in mind, and knowing that a turbo setup on an engine burning oil would be bad, I decided to tear down today. The cam lobes were a little iffy, but i would think within specs and it wouldn't make me burn oil if it was bad. When I got the head off, I found this (after some sad wiping of the pistons with a rag): Looks a little dirty, but overall not too bad, right? My concern is that the cylinder walls were glossy. This was (I am guessing) because of the large amount of oil on the cylinder walls (from cranking the engine to TDC without firing? idk). My first thought was, where the heck is the cross hatching? I've seen pictures of a few engines with very visible hatching. So I went hunting for it! After a good wipe with a rag, I managed to get the bore dry and got to this point: Now this is obviously hatching, but my flash from my camera is giving them too much credit. They are definitely not that visible to the eye. Here's a couple more for reference. So after that long story, I ask for your opinion. Do you guys think my problem was crappy rings? or do I need to hone it, and ring it? Are my cylinders ok? Thanks in advance, I always appreciate the help from you guys. Edited December 3, 2014 by Boog Quote Link to comment Share on other sites More sharing options...
Leon Posted November 30, 2014 Share Posted November 30, 2014 Your valve stem seals are leaking. Who did the "Stage 3" head? Please don't say Datsun Parts LLC... Did you perform a compression and leak-down check before tear-down? If those results were good, I'd change the stem seals in the head and put it back together. In fact, stem seals can be changed in-car with the right tools... Quote Link to comment Share on other sites More sharing options...
Boog Posted November 30, 2014 Author Share Posted November 30, 2014 Well I bought the stage 3 head from my mechanic, I have no idea what was done to it at the time, I truly was car clueless. I didn't do a leakdown test, but I did do a compression test and if I remember correctly, I did it with a hot engine, and the best reading I got was 115 or 110. I'll have to find the paper where I wrote it down, but it was very low. Quote Link to comment Share on other sites More sharing options...
Boog Posted November 30, 2014 Author Share Posted November 30, 2014 I also just looked up valve stem seal symptoms, and I found a guy with a 77 that burned oil on deceleration, which is my problem, and fixed it with valve stem seals.....definitely should have done the compression test with the teaspoon of oil. Is it more likely to be seals or rings? Quote Link to comment Share on other sites More sharing options...
Xnke Posted November 30, 2014 Share Posted November 30, 2014 Check for a ring ridge at the top of the bore. Has the bottom end been rebuilt previously, or is this a Nissan assembled bottom end? Yes, smoke on decel can be valve stem seals. Also it will puff blue smoke on startup after sitting overnight, that's another sign. Quote Link to comment Share on other sites More sharing options...
Boog Posted November 30, 2014 Author Share Posted November 30, 2014 Sorry, can you explain a little more on what the ring ridge would be? Are you saying just visually inspect the top ring? Its been so cold here lately my latest startups it blows more condensation whitish winter startup smoke than anything blue. It is the Nissan bottom end, nothing has been touched. ~180k miles on it. When I had my head installed years ago, I remember the mechanic saying something about how the bottom end was a little dirty, but in good shape. Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 30, 2014 Share Posted November 30, 2014 My current setup (stock) has been burning oil, but only on backpressure. I'll be going down a hill, engine braking, and my car will spew blue smoke. From the blue and the smell, I definitely know it's oil. I also had a "Stage 3" head put on a year or so ago, The lobes were a little iffy, but i would think within specs It's been fine for years (how many and how many miles since?), or you just noticed it now? Or you just started engine braking on the hills? I don't think that cylinder pressure measurements will pick up worn oil rings, which would be the rings causing the problem. A leakdown test won't show it either. Stage 3 might just be somebody's cam grind label. Did you buy the head used or new? If the seals are leaking, the backs of the valves will be pretty oily and grimy, I believe. The seals on my old high mileage head let oil past them on to the valves just sitting on the bench after I removed it. I don't think that new ones will do that. Iffy lobes are not good. Quote Link to comment Share on other sites More sharing options...
Boog Posted November 30, 2014 Author Share Posted November 30, 2014 I've put about 4000 miles on the new head. The oil burning on engine braking has gotten worse and worse over the past year. It also burns oil under hard acceleration, per a friends account of the smell when he followed me up an onramp. I bought the head through my mechanic, so I have very little knowledge of what has been done to it. I'm sure this info oisnt very helpful for figuring out head condition, so I'll go take some good pictures of the head and post back here within the hour. Quote Link to comment Share on other sites More sharing options...
Boog Posted November 30, 2014 Author Share Posted November 30, 2014 (edited) *Sorry about the picture size, I posted these in a rush, I can edit my post later tonight to make them smaller. Until then, please zoom out, haha.* Alright, here are the pictures. First are of the springs and rockers, as well as a couple looks at the cam. Next is the intake ports, as well as one good look at a valve. You can see the porting scratches. Last is an exhaust port. Edited November 30, 2014 by Boog Quote Link to comment Share on other sites More sharing options...
Xnke Posted November 30, 2014 Share Posted November 30, 2014 (edited) Those ports look clean enough...not sure if the valve stems have oil coating them or just residue. Ring ridge...you seen in your photos of the bore walls where the rings don't come up any higher? There is a very clear mark there. If you can catch a fingernail there, then you have a bore issue. Would be uncommon at only 180K, but certainly possible. If you can't hang a fingernail on the ring ridge, then try this Tip the cylinder head up with the valve cover bolted on with the gasket, and pour a little oil in the valley so that the valve stems at the back of the head are submerged in oil...they should have what's called "positive contact" seals on them, so with just gravity pulling, you should not get oil leaking down into the ports in any great amount...if you get any at all. Bronze guides do run a little looser and wear out quite a bit faster than the stock cast iron guides, so you will likely get a little oil. It should not be very much at all! Leave the head tipped up like this over some paper towels for 30 minutes, and then come check for oil seeping past the guides. If you get more than a drop or three, it would be a good idea to check into changing the valve seals first. A set of the fel-pro Ford 2.8L Capri seals can be tricky to put on but will not pop off or leak like some of the aftermarket stock replacement seals can. Edited November 30, 2014 by Xnke Quote Link to comment Share on other sites More sharing options...
Boog Posted December 3, 2014 Author Share Posted December 3, 2014 Ok, so I felt for ring ridge. On cylinders 3-5, there was nothing. on cylinder 2, there was the slightest hint of a ridge, barely barely barely. 1 and 6 were TDC so no testing. As for the head test, you want me to just put the valve cover on, pour in half a quart of oil into the filler hole, and see if it drops down into the valves? Sorry if I am not grasping what the guides and such are, I'm not very educated on head parts yet. Since I am pulling the oil pan to get a oil return line bung welded on, I think I'll go ahead and do piston rings and lightly hone the cylinders, if there isn't a problem with doing that.....is there a reason not to while the pan is off and I have access? Quote Link to comment Share on other sites More sharing options...
NewZed Posted December 3, 2014 Share Posted December 3, 2014 (edited) As for the head test, you want me to just put the valve cover on, pour in half a quart of oil into the filler hole, and see if it drops down into the valves? Sorry if I am not grasping what the guides and such are, I'm not very educated on head parts yet. That's close. He wanted you to tilt the head so that the oil would be completely covering a valve seal. But it looks like your engine is still in the car so that might be difficult. Added a picture showing where the valve seals are (they sit around the valve stem and on top of the valve guide, where it passes through the head to the combustion chamber, inside the valve springs) and a squiggly line representing oil level for the test. There's a thread in the FAQ, L-Series section, about honing and re-ringing. Probably worth checking those valve seals first though. Since you have the engine apart and it's been sitting, take a good look at each valve to see if oil has been leaking by. http://forums.hybridz.org/topic/81528-replacing-piston-rings-with-the-engine-in-the-vehicle-l-series-faq/ Edited December 3, 2014 by NewZed Quote Link to comment Share on other sites More sharing options...
Boog Posted December 3, 2014 Author Share Posted December 3, 2014 Actually the head is off, so that test is doable. I will give it a shot as soon as I can. My main question is, given the condition of my cylinders as seen above, is it worth doing the rings and honing? I feel like the valve seals have a higher chance of being bad than the pistons, given the many accounts of these bottom ends doing 300k miles no rebuild (i'm at 165k). Quote Link to comment Share on other sites More sharing options...
Xnke Posted December 3, 2014 Share Posted December 3, 2014 More than likely it is bad valve stem seals. As I said...the bronze guides don't last as long as the cast iron stockers either. Did you do a wet and dry compression test before you tore it down? Quote Link to comment Share on other sites More sharing options...
Boog Posted December 3, 2014 Author Share Posted December 3, 2014 I did a compression test after driving, and i wrote down the numbers but I lost the sheet. I remember all of them were under 120, maybe down towards 110? Definitely no higher than 120, and i remember thinking "wow, these are pretty low". Quote Link to comment Share on other sites More sharing options...
Leon Posted December 3, 2014 Share Posted December 3, 2014 (edited) I did a compression test after driving, and i wrote down the numbers but I lost the sheet. I remember all of them were under 120, maybe down towards 110? Definitely no higher than 120, and i remember thinking "wow, these are pretty low". That could easily have been the valves out of adjustment and/or stretched timing chain. Did you check valve lash and cam timing? I don't want to jump to any conclusions but if the necessary diagnostic steps haven't been taken, it's difficult to recommend the next course of action. If you really want to know whether you should rebuild the bottom end, you now need to mic the bore for nominal size and taper. I can't tell you anything about the bearings unless you've been monitoring oil pressure. If it's an original Nissan bottom end and it hasn't been run low on oil or overly abused, there's a pretty good chance that the bearings are fine. Edited December 3, 2014 by Leon Quote Link to comment Share on other sites More sharing options...
NewZed Posted December 3, 2014 Share Posted December 3, 2014 Or an enlarged combustion chamber. The head's been worked on. "Stage 3". Could also be the gauge. Using a metal adapter tube instead of the hose will drop a 180 down to about 120. Quote Link to comment Share on other sites More sharing options...
Xnke Posted December 3, 2014 Share Posted December 3, 2014 I know you did a compression test...did you do one with a teaspoon of oil added to the cylinder? Both the dry and wet test are needed to rule out rings without a leakdown test. Also...not every gauge set reads the same. Did you write down each cylinder, noting if any cylinder reads more than 10% (personally I go 5%) different than the others? Quote Link to comment Share on other sites More sharing options...
Boog Posted December 4, 2014 Author Share Posted December 4, 2014 I did not add oil, so unfortunately I do not have results of a leakdown test. I do know though that the readings were within 10% of each other. Is there any reason not to do a re-ring and hone? As for oil pressure, I'm pretty sure my sending unit is messed up, every time I start it the readings are fine, but once I start driving and have one decent pull to 4k, when I get off the gas and let it idle the needle goes negative. It seems to me like I have some gunk in the sending unit. Quote Link to comment Share on other sites More sharing options...
Xnke Posted December 4, 2014 Share Posted December 4, 2014 (edited) If it's an original Nissan-assembled engine, it has higher quality components than you're likely to be able to find nowadays...you can't get Nissan bearings or ring sets anymore for these. You can still get quality parts, don't get me wrong, but you really have to hunt for them. If it was me, I would disassemble and check dimensions and clearances, and if they were still in-spec, reassemble and go on with it. If they were out-of-spec, then I would do a complete rebuild. It does have nearly 200K on it, depending on the life it's had, it may be time. If the compression test was within 10%, then you likely have decent compression ring seal, so it is down to either oil rings or valve seals. Valve seals are twenty bucks, headgasket is twenty bucks, so you could be back on the road and not smoking for under 50$. Or you could drop 800$ or more on a complete bottom end, plus 50$ for the same headgasket and valve stem seals. I would order a set of the Ford valve seals and install them, carefully, and then reassemble the valve train and the engine with a new headgasket, and run it. Chances are good your smoking problem will be solved. Edited December 4, 2014 by Xnke Quote Link to comment Share on other sites More sharing options...
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