Oil in cylinder but no broken rings

[JohnJL]

I noticed a lot of oil on my #2 plug, it would fire intermittently and compression figures were inconsistent.

I removed the heads and found a lot of oil pooled in the #2 and a little in the #3 cylinders. Pics attached below.

I suspected broken rings but found them all intact and in apparently good condition. These are new JE pistons, the rings they came from (I dont remember deves, goetz or something else?) and new perfectbore cylinders. The motor has 3 track days and ~12 hours tuning on the dyno. The cylinder walls show slight marking but not scratching.

The #1, #4, #5 and #6 cylinders were all dry, no oil in the chamber.

Are the rings on those two cylinders in need of replacement? THere is no apparent damage to them but perhaps its not an issue I can see.

Any other suggestions?

[Flieger]

Valve guides?

[lindy 911]

Looks like too much oil to be guides, can you post a pic of the oil ring in the cylinder. Did you measure the gap before install? Show a pic of the "marking" in the cylinder.

[Steve@Rennsport]

John,

Might be guides (I've seen that before) but I'd check some other things as well.

1) Whats your piston-to-cylinder wall clearances?

2) Ring gaps?

3) Did you inspect the ring surfaces with a strong magnifying glass? You wouldn't believe what I've seen with some Goetze rings recently.

[lindy 911]

One other thing about oil-ring; installation position. The gap needs to be up or when the motor is cold it'll let oil by. When the motor sits the oil will drain back from the tank into the case and make its way into the cylinders on the back side of the pistons. If the oil ring gap is down oil will pass into the combustion chamber. Ask me how I know.

[HawgRyder]

When I assemble engines...I always check the ring gap position on each cylinder.
Starting with the "3 piece" oil ring...the gaps of the two thin rings are at 120deg from each other...and oriented to the 10 and 2 oclock position...and the middle part of the ring...the "expander" gap is at the 6 oclock position.
Then the 2 compression rings go to the 4 and 8 oclock positions.
You might also check that the top ring is not on the exhaust side..(just my preference).
Hope this helps.
Bob

[JohnJL]

hThanks guys, here are some answers;

The ring end gaps are .559mm on each ring. I staggered the gaps on assembly. I didnt notice if they were still staggered on disassembly.

The rings were properly oriented on the pistons.."TOP" marking on the oil rings facing the piston dome.

The marking is very subtle, you cant see it in pictures.

The pistons are 97mm, and the cylinders read 97.83mm inner diameter (on my calipers). Both cylinders and pistons are new.

There was oil in the exhast port of both #2 and #3 but not #1. This motor has sat not running and in various orientations on the stand for the last 6 months.

I took the heads apart tonight, the exhaust guides were "tight," as in they move smoothly without binding and there is no play side to side with the springs removed.

The intake valves have the "slightest" bit of play. They are not as tight as the exhaust valves, when I remove the springs and move the intake valve 10mm into the head I can feel the tiniest bit of play when I wiggle the valve back and forth. I dont have a tool to measure this, but I'd guess it to be .025mm. Thats comparing a .1mm valve lash.

This is the same on 1, 2, and 3 heads. Only #2 and #3 had oil in the cylinders. THe heads were done by PR Technology in Sydney prior to the build.


There were no anomalies in the oil or signs of heat in the heads, other than the large amount of oil obviously pooling and burning in the cylinders.

Any other thoughts?

[Steve@Rennsport]

Originally Posted by JohnJL

The pistons are 97mm, and the cylinders read 97.83mm inner diameter (on my calipers). Both cylinders and pistons are new.

Calipers are inadequate for determining clearances; you need a dial-bore gauge and a micrometer. Measure the top ring land clearance first, as thats one of the biggest areas of concern. Many JE's are fitted too loose and that causes problems.

I took the heads apart tonight, the exhaust guides were "tight," as in they move smoothly without binding and there is no play side to side with the springs removed.

The intake valves have the "slightest" bit of play. They are not as tight as the exhaust valves, when I remove the springs and move the intake valve 10mm into the head I can feel the tiniest bit of play when I wiggle the valve back and forth. I dont have a tool to measure this, but I'd guess it to be .025mm. Thats comparing a .1mm valve lash.

Again, the ONLY way to know what you have is to measure the stems and guide bore ID's. "Kentucky Windage" doesn't work when trying to accurately troubleshoot these kinds of issues. Intake guide clearances aref normally tighter than exhaust guides so you should look into this.

[JohnJL]

Originally Posted by Steve@Rennsport

Calipers are inadequate for determining clearances; you need a dial-bore gauge and a micrometer. Measure the top ring land clearance first, as thats one of the biggest areas of concern. Many JE's are fitted too loose and that causes problems.

Again, the ONLY way to know what you have is to measure the stems and guide bore ID's. "Kentucky Windage" doesn't work when trying to accurately troubleshoot these kinds of issues. Intake guide clearances aref normally tighter than exhaust guides so you should look into this.

Hello Steve, thanks for your help.

Unfortunately I dont have a bore gauge, but I do have a fairly complete set of outside micrometers. When you say "the top ring land clearance" could you rephrase that description or post a pic?

I know my intake valve guide description is poor. I am fairly sure that that amount of oil would not have come from the intake valve guides though. 2 reasons...first is they are still fairly tight...they make a strong vacuum against a finger when removed. I dont see that much oil leaking by. The second reason is I didnt see much or any oil in the intake port on the backside of the intake valve. If the intake guide was leaking I'd expect to see oil behind the valve. I do see evidence of a lot of oil in the exhaust port. It looks like oil is coming in through the rings and getting pushed out the exhaust port.

I'm curious about my ring gaps. These rings came with the pistons, but having checked some posts now and JE's site those gaps seem quite wide. I did not file them on installation. There should be no wear on the cylinders, they are fresh from Perfectbore and still have the hatching.

Thanks guys.

[JohnJL]

OK, I got better cylinder/piston measurements.

Pistons mic to 97.16mm

Cylinder inner bores mic at dead-nuts 98mm measuring across the outside of a ring installed and measured through the cylinder skirt cut-outs.

[JohnJL]

Have emailed the JE Piston Tech guys for their comment here....

[Steve@Rennsport]

Originally Posted by JohnJL

Hello Steve, thanks for your help.

My pleasure.

Unfortunately I dont have a bore gauge, but I do have a fairly complete set of outside micrometers. When you say "the top ring land clearance" could you rephrase that description or post a pic?

Measure the diameter of the piston above the top ring groove; this is also known as the "head land". Sometimes JE uses a little too much clearance here that causes some loss of sealing.

[JohnJL]

Steve, that's where I measured 97.16mm with a micrometer this time. The pistons are marked with "97M" on the bottom of the dome.

My ring gaps are .559mm or .022" which is ~50% wider than the .015" the JE Piston site and build sheet state. I recall seeing somewhere 1MM as being Porsche's max acceptable gap. Are ring gaps a case of variations not being an issue as long as they are within range? Could the gap be leaking that oil into the cylinder?

[lindy 911]

When looking at the piston in the cylinder while the motor is on the stand, the oil ring gap should be pointed at about 2 O'clock on one and 10 O'clock on the other (there are two). If the gaps were facing down, oil can seep by them when the motor is at rest.

[JohnJL]

Originally Posted by lindy 911

When looking at the piston in the cylinder while the motor is on the stand, the oil ring gap should be pointed at about 2 O'clock on one and 10 O'clock on the other (there are two). If the gaps were facing down, oil can seep by them when the motor is at rest.

Thanks Lindy, I did install the rings with the gaps properly staggered, I didnt notice on disassembly though if they had rotated.

[lindy 911]

Not likely they rotated but it's possible I guess. Did you use a thermal barrier coat on the piston top by chance? I've recently learned this is a big no-no, especially with JE pistons. The thermal barrier doesn't allow the piston to absorb enough heat so that it can grow into the cylinder bore. The end result is a loose fitting piston with piston slap and not able to seat the rings because they are not square to the bore. JEs are known for making some noise when cold but as they warm up and expand into the bore they quiet down.

[Two Rivers]

One other place to look is the valve guide bore. I had a set of heads that the PO had rebuilt and when the guides where pressed out it had scraped deep groves in the guide bores.
The engine smoked on deceleration and at idle.Looked like yours when I pulled the heads. I was surprised at how much oil passed between the guide to head bore.
The repair was oversize guides.

[stownsen914]

I'm a little late to this party, but couldn't the oil in the cylinder be the result of pooling from storage? I've seen this in two different race cars I've owned that have large capacity, front mounted oil tanks. I understand that this happens because the level of oil in the tank equilibrates over time with the level of oil in the engine sump by slowing trickling through the oil pump, eventually getting into the cylinders. I also understand that it doesn't necessarily require worn out rings or valve guides for this to happen, since some clearance is normal even for new parts. For my cars when I've gotten this, I get significant smoke upon start up, and it disappears after a few minutes. I avoid having this pooling by storing the rear of the car on jack stands or wheeled up on some boards.

When the engine was oil fouling, did it reduce after the first few minutes by chance?

Scott

[CaptainCalf]

Originally Posted by lindy 911

one other thing about oil-ring; installation position. The gap needs to be up or when the motor is cold it'll let oil by. When the motor sits the oil will drain back from the tank into the case and make its way into the cylinders on the back side of the pistons. If the oil ring gap is down oil will pass into the combustion chamber. As me how i know.

+1

[Walt Fricke]

I echo Scott's suggestion. One 914-6 race car I know of had a big ball valve installed in the return line from the front sump. In turn, an electric switch was installed which disabled the ignition unless the valve handle was turned to the on/flow position. Just in case.

When I've jacked my track car with its 4 gallon front tank up by the front to work up there, sometimes I get excess oil in the crank case, and I think I've even had some get into the heads in amounts enough to require pulling plugs.

I can also pull the engine without draining the oil. I spill some, but not much. But I have to remember, with the engine on the engine stand, not to turn it too far, or at least for too long.

Still, with that much oil I think it pretty much has to be getting in via the rings. Ring gaps tend to rotate around despite our efforts to install them in logical positions. I think the crosshatch angle may have something to do with that.