Burning oil

[Charlesvolare]

I have a small block that's smoking at idle, but only after it's warmed up. Nothing I can tell on initial startup or while driving around. It's an la 360 with magnum heads, 10.8:1ish compression. Kb107 pistons, moly rings, fresh heads (new +.100" valves, spring pockets cut, deck surface cut). Rebuilt it last December, fresh hone and top compression rings gapped to kb's nitrous spec of .032" (I rebuilt because a ring butted and popped a ringland off, wasn't taking any chances). First start was January 3rd. Roller cam, easy break-in just to seat rings. It drove great, 500 miles the first month no problems.

Did the first oil change and did an autocross event on February 1st, the first time really driving hard on the fresh engine. One of my buddies noticed it was smoking a little and said something. Spent the next month trying to figure it out. It didn't do it before that day and has done it ever since.

I've pulled a few springs and checked valve seals, good. No noticable oil smoke on initial startup either so I'm crossed valve seals/guides off the list.

Only seems to burn oil at idle, so I pulled the intake to check the gasket. Heads are milled a little so thought maybe the intake gaskets could be leaking. Replaced the intake (chinese crosswind) with new gaskets and no change. Got a deal on an Edelbrock 7577 (Edelbrock rpm air-gap for magnum heads). Put that on, no change.

Unplugging and blocking the pcv seems to make it smoke more. No excessive blow-by. Capping off the breather and pcv with vacuum gauge on dipstick, it slowly builds pressure. Not very quickly, but enough to for sure determine no vacuum leak at the intake. I can see oil on top of the pistons looking into the sparkplug holes, as well as through a small boroscope camera thing.

Did a dry/wet compression test, after it was warmed up: (first number was dry, second wet)
1-190 210
3-205 *
5-170 210
7-200 210

2-200 210
4-210 *
6-200 210
8-180 210

From all of this, I'm guessing I have a ring problem. 1, 5, and 7 are hurt somehow. I had 500 miles on it without any problem, no smoking or anything. Definitely thought the rings would be well seated by then, especially moly rings. Drove it hard for the first time, started smoking.

Any ideas to what would cause sudden ring problems like this? Or any other suggestions as to what it could be?

Autocross event:


Smoking at idle:


Cylinder hone

 

[brian6pac]

How many miles scents rebuild ?

 

[Phreakish]

Are you certain it's oil? How much oil does it consume and how quickly?

Overly rich or lean mix can "smoke" too. Plugging the pcv on a rich mix will make it richer and smoke more.

Take some pictures of your sparkplugs and post them. If there's oil, it will be obvious.

 

[yellow rose]

Why no PCV? You should have one.

 

[Joey4speed]

Are you certain it's oil? How much oil does it consume and how quickly?

Overly rich or lean mix can "smoke" too. Plugging the pcv on a rich mix will make it richer and smoke more.

Take some pictures of your sparkplugs and post them. If there's oil, it will be obvious.

Agree, the used plugs should tell a story.

 

[Joey4speed]

Why no PCV? You should have one.

He has a breather and PCV, he just capped it for testing.

 

[nm9stheham]

Not sure why you have ruled out valve stem seals....??? The fact that the oiling increases with the PCV blocked could well indicate it is in the seals/ guides.

I'd pull the intake or work the borescope down the intake runners and inspect the tops of the intake valves. If they are reasonably clean, then it is from the cylinders/rings.

So just a hone job on the cylinders? Did you measure the cylinders for taper and out-of-roundness? Your 2nd compression ring does more for oil control than it does to seal compression. So the rings may not be sealing as well as you think due to the cylinders not be straight and true.

Any chance that the 2nd rings got installed upside down? Many/most of them have a specific 'twist' designed into them that makes them more effectively scrape oil downward off the cylinder walls. If they are upside down, the 2nd rings' oil scraping ability is lost.

 

[Charlesvolare]

How many miles scents rebuild ?

500 miles until it started and then maybe another 200 at most from driving it since.

Are you certain it's oil? How much oil does it consume and how quickly?

Overly rich or lean mix can "smoke" too. Plugging the pcv on a rich mix will make it richer and smoke more.

Take some pictures of your sparkplugs and post them. If there's oil, it will be obvious.

I haven't driven it much since it started, and it doesn't seem to do it while driving around. Only stopped at idle, and even then it not immediate. It has to idle a few seconds and then it starts. So I haven't had to add any since it started. I added a little trans fluid to see if Vale seals would swell and stop it, but it never read low enough for me to add oil. I'd have to let it sit in the driveway and smoke out the neighbors for a while to see a difference on the dipstick.

The smoke definitely looks blue to me.

These first two at after getting to temp and burping the coolant system after installing the new Edelbrock manifold + a short .5 Mile drive around the block. I have the plugs I drove with from the rebuild up until the manifold swap that I can take a picture of when I get home, but they were fouled enough for it to have a miss.

ip

 

[Charlesvolare]

Not sure why you have ruled out valve stem seals....??? The fact that the oiling increases with the PCV blocked could well indicate it is in the seals/ guides.

I'd pull the intake or work the borescope down the intake runners and inspect the tops of the intake valves. If they are reasonably clean, then it is from the cylinders/rings.

So just a hone job on the cylinders? Did you measure the cylinders for taper and out-of-roundness? Your 2nd compression ring does more for oil control than it does to seal compression. So the rings may not be sealing as well as you think due to the cylinders not be straight and true.

Any chance that the 2nd rings got installed upside down? Many/most of them have a specific 'twist' designed into them that makes them more effectively scrape oil downward off the cylinder walls. If they are upside down, the 2nd rings' oil scraping ability is lost.

I've been trying to figure it out for over a month. Valve seals were new a few years ago, I pulled a few to inspect, put trans fluid in oil to try to swell them. It doesn't smoke when the engine is cold or on initial startup. All of that combined the the wet/dry compression test is what's leading me to rings.

I didn't check for taper, it was a quick tear down and reassembly with new rings and bearings and replacing the piston that was missing a chunk. It ran great before and ran great for a month after. Would cylinder taper be something that'd show up immediately though?

I assembled everything myself and I'm 99.9% sure the rings are installed in the correct orientation.

 

[512Stroker]

500 miles until it started and then maybe another 200 at most from driving it since.



I haven't driven it much since it started, and it doesn't seem to do it while driving around. Only stopped at idle, and even then it not immediate. It has to idle a few seconds and then it starts. So I haven't had to add any since it started. I added a little trans fluid to see if Vale seals would swell and stop it, but it never read low enough for me to add oil. I'd have to let it sit in the driveway and smoke out the neighbors for a while to see a difference on the dipstick.

The smoke definitely looks blue to me.

These first two at after getting to temp and burping the coolant system after installing the new Edelbrock manifold + a short .5 Mile drive around the block. I have the plugs I drove with from the rebuild up until the manifold swap that I can take a picture of when I get home, but they were fouled enough for it to have a miss.
View attachment 1715487368 ipView attachment 1715487375

The pic's of your plugs do show signs of an oiling issue.
Which holes did they come out of? Cylinder numbers?
The plugs that look black and gummy are the offenders.
Start with the top end and work your way down.
My guess at this point is rings, that's a lot of cylinder pressure to deal with.

 

[Charlesvolare]

Are you certain it's oil? How much oil does it consume and how quickly?

Overly rich or lean mix can "smoke" too. Plugging the pcv on a rich mix will make it richer and smoke more.

I also have a wideband on it. I got it to idle nice around 13.5:1, cruise at 14:1, and 12:1ish under fill throttle, all transitioning fairly smooth. The sensors are fouled now and read lean no matter what, but I do have plugs to read.

 

[Charlesvolare]

The pic's of your plugs do show signs of an oiling issue.
Which holes did they come out of? Cylinder numbers?
The plugs that look black and gummy are the offenders.
Start with the top end and work your way down.
My guess at this point is rings, that's a lot of cylinder pressure to deal with.

The ones in the vertical are 1-3-5-7 bottom to top, 1 and 5 definitely corresponding with the dry/wet compression test I did. #1 gained 20psi and #5 gained 40psi.

The horizontal picture is 2-4-6-8 left to right.

 

[Charlesvolare]

I figured it was rings, but what could cause it to suddenly do this? It was good up until that day, smoked since. That's what's stumping me.

 

[512Stroker]

I figured it was rings, but what could cause it to suddenly do this? It was good up until that day, smoked since. That's what's stumping me.

When you started gett'n on it did it ever detonate?
With kind of cylinder pressure it may have broken some rings and/or lifted some ring lands.

 

[yellow rose]

I figured it was rings, but what could cause it to suddenly do this? It was good up until that day, smoked since. That's what's stumping me.

If it is smoking when the vacuum is high it's valve seals, guides or the intake manifold is leaking around the ports.

 

[Charlesvolare]

If it is smoking when the vacuum is high it's valve seals, guides or the intake manifold is leaking around the ports.

I tried to cover everything in my first post on the thread. I spent a month hoping it was either of those, because that would be a fairly simple fix. Just upgrade to a set of aluminum heads. But I'm fairly confident I've tried everything to rule those out.

If it was seals/guides, wouldn't it do it at startup, cold, decel when driving? It's doing neither, only after it's warm and only after it sits at idle for a few seconds.

I've had two different intakes, three sets of gaskets. Crankcase is not pulling vacuum at idle, it's building pressure. But I pulled intake and replaced gaskets the first time thinking that was it, second time to double check ($20 for gaskets, an hour of time, no big deal), third time to replace with a new Edelbrock manifold that I know the angles would be as correct as possible.

 

[Charlesvolare]

When you started gett'n on it did it ever detonate?
With kind of cylinder pressure it may have broken some rings or lifted some ring lands.

It's possible it detonated, I don't remember noticing but I also I had the cutouts open to show off to all the Miata's that were there, so it was a little hard to hear.

I was looking at the piston that blew apart last fall and saw this:

The top had pushed down into the ring groove. I guess if it did detonate pretty bad it could've pinched a ring and possibly damaged the bore or something...

 

[512Stroker]

It's possible it detonated, I don't remember noticing but I also I had the cutouts open to show off to all the Miata's that were there, so it was a little hard to hear.

I was looking at the piston that blew apart last fall and saw this:
View attachment 1715487512
The top had pushed down into the ring groove. I guess if it did detonate pretty bad it could've pinched a ring and possibly damaged the bore or something...

Bingo!

 

[nm9stheham]

Taper in the bores can wear rings out pretty quickly. I did a few re-hones in my early/poor years, and the rings never lasted worth a darn. I don't do anything but fresh bores anymore. You don't need to second-guess yourself later.

If the valve stem seals are bad, you sure ought to see it when you press on the gas after a deceleration; it may or may not be visible during decel, 'specially out there in the flatlands. You 100% need to have someone follow you to observe when the oil smoke appears. You can't see it all from there, especially with the outlets so far under the car. Get one of your buddies to follow you and go through a routine of different checks.

And with the oil thicker at cold start, you may well not see it then, regardless of where it is going.

If I read your posts right, when the PCV is not connected, the crankcase is going to build some pressure regardless. so that is not conclusive IMHO.

 

[yellow rose]

Taper in the bores can wear rings out pretty quickly. I did a few re-hones in my early/poor years, and the rings never lasted worth a darn. I don't do anything but fresh bores anymore. You don't need to second-guess yourself later.

If the valve stem seals are bad, you sure ought to see it when you press on the gas after a deceleration; it may or may not be visible during decel, 'specially out there in the flatlands. You 100% need to have someone follow you to observe when the oil smoke appears. You can't see it all from there, especially with the outlets so far under the car. Get one of your buddies to follow you and go through a routine of different checks.

And with the oil thicker at cold start, you may well not see it then, regardless of where it is going.

If I read your posts right, when the PCV is not connected, the crankcase is going to build some pressure regardless. so that is not conclusive IMHO.

This made me remember something. I had an engine I bought out of a wrecking yard in 1980. It was "fresh" and it sounded good.

After about 700 miles or so, every time I pulled up to a stop light, the engine would spring a leak. No matter what I sealed and resealed, it would find another place to leak. Eventually it started leaking out of the timing cover seal and pushed the pan gasket out.

So I pulled it out and took it apart. And some whiz bang used a ridge reamer on a standard bore to the point that to fix it required a .040 over bore.

It had .010 taper as well. Every single top ring was broken.

That's what broke the rings. No way would you ever be able to seal that pig up the way it was. The funny thing was other than the oil it leaked all over the place, it didn't use oil.

 

[Charlesvolare]

I didn't think about the oil thinning at temp

So two possible explanations:
1. Rings. Possible detonation damaged rings/bore. Explains result of compression test. And suddenness of symptoms.

2. Valve seals/guides. Heads probably have 200,000 miles, possibly original guides. I got them at 180,000 miles and have touched everything but the guides. When engine is cold, oil is too thick to get past seals/guides. After it's warmed up, oil is thin enough to seep past under idle vacuum. Need to have someone follow me while driving and watch the exhaust. What could be a possible "switch" to cause the smoking? Guides would wear slow and slowly open clearances. I've been running Driven GP-1 15w-40 synthetic since rebuild.

Are there any better ways to test the two? Look at the tops of the intake valves? Any more symptoms of the two? Anything I've explained happening that doesn't make sense for one or the other?

 

[nm9stheham]

Just the bore taper and out-of-roundness. And flipped 2nd rings. Boy, 200K on the guides..... It'd be pretty unexpected be very tight anymore.

It had .010 taper as well. Every single top ring was broken.

That's what broke the rings. No way would you ever be able to seal that pig up the way it was. The funny thing was other than the oil it leaked all over the place, it didn't use oil.

Funny how that works...LOL. I just think that when you get some taper in the bore, the constant flexing of the rings just does them in in quick order.

 

[yellow rose]

Just the bore taper and out-of-roundness. And flipped 2nd rings. Boy, 200K on the guides..... It'd be pretty unexpected be very tight anymore.

Funny how that works...LOL. I just think that when you get some taper in the bore, the constant flexing of the rings just does them in in quick order.

Yup. Rings detest changes in bore diameter. And the thicker the rings, the less they will tolerate bore geometry issues.

That thing was a mess. I haven't thought about that engine in years. It had some unknown cam it that wouldn't idle well below 1200 and at that, it was just nasty. And idle doesn't bother me, but the girlfriend hatred it. It would shake the car so bad the visor on her side would drop down. Not a big deal, unless you were her. Then is was an absolutely deal breaker.

And, it was just nasty to about 1900 and then it would clean up a bit and by 2500 it was making steam. Unfortunately at 4500 it was all over but the crying. At the time I figured it was turning 7500 (hell, I thought I was) but my dad drove it and said its lucky to be turning 5500. So I went and bought a nice Stewart-Warner tach and damned if the old man was off by a grand. 4500 was all she had.

I hated that oil spewing turd.

 

[Charlesvolare]

I remembered today when I tore down for the rebuild, cylinders 2 and 7 also had broken top rings (besides #3 that blew the ringland) the ring gap was way too tight and lasted through two years of pretty hard abuse and bad tuning while I figured out this hot rodding stuff on my own. I definitely remember it having more blow-by than it does now and it didn't smoke at all.

Ring gap is good, tune is even more conservative than it has ever been. Just some thoughts I had on it today, really hoping it's valve guides/seals.

 

[512Stroker]

I remembered today when I tore down for the rebuild, cylinders 2 and 7 also had broken top rings (besides #3 that blew the ringland) the ring gap was way too tight and lasted through two years of pretty hard abuse and bad tuning while I figured out this hot rodding stuff on my own. I definitely remember it having more blow-by than it does now and it didn't smoke at all.

Ring gap is good, tune is even more conservative than it has ever been. Just some thoughts I had on it today, really hoping it's valve guides/seals.

Are you hitting this thing with a bottle?