Oil Smoke - Input - ZR-1 Net Registry Forums

Ccmano · 02-20-2018

Looking for some collective wisdom. Have to admit I’m a little stumped on this one. First some backgound.

My car is an ultra high mile (181k) one owner 1990 car I bought last year as a long term restoration project. Although, the car is generally in outstanding condition. Some of you may remember the photos I posted. I’ve be working on her and have recently replace the transmission, clutch and flywheel (presenting their own issues). Also, adding headers and exhaust. Last year, the compression test was excellent averaging 190-195psi across all cylinders (I’m at 4500ft so add few more psi for sea level). It idles smooth and runs very strong. No signs of smoke of any kind other than when flogging her at full throttle. Even then just a hint of smoke which I consider normal for a 1990. I run Mobile 1 10w40 High Mileage oil.

Dominic and I have been working since the first of the year tuning the engine for the current mods. The results have been outstanding. The car is responsive and strong. The weather here has been good allowing me to do several 40 mile data logging runs a week since then. The only issue has been an intermittent code 64 (right O2 Sensor lean) at idle after a long drive.

Suddenly, about three weeks ago I started noticing light wisps of blue smoke accelerating lightly from a stop, only when the car is hot. This started to increase since then. I noticed it particularly on a long coast down in 4th gear coming down a long grade to a stop at the bottom. No smoke while coasting but when I accelerated away from the stop I got a good cloud. I’ve been monitoring it since and it is to the point where once the car is hot I get a good plume if I goose the throttle. There is no smoke at static idle though. There is no smoke at all while the engine is cold, even under acceleration. The smoke comes exclusively from the right exhaust.

So I started looking at the usual suspects to try and find the cause. Valve guides are unlikely because they don’t fail suddenly like this and generally cause smoke at startup when cold. My car doesn’t do this. Next is the PCV system and the camcover breathers. Breathers are clean and generally dry. I removed the entire PCV system and found it to be in great shape with functioning PCV valves and no deterioration of the rubber pieces. All seals are good. I cleaned the PCV valves as a precaution. While there was oil in the system, there was not enough for concern. I even ran the car with the PCV system disconnected and still had the smoke. Related to the PCV system is excessive blow by caused worn rings. With the car idling there is no pressure or air being pushed out of either the oil cap opening in the cam cover or the dip stick tube. Nothing.

Today I conducted another compression test, to my surprise it was better than last time. Averaging 200psi on the right side and 190psi on the left. Again, I’m at 4500ft, so add a few psi for sea level comparision. None of the cylinders stood out. I’m thinking the right left difference is timing chain stretch.

Looking at the plugs, particularly the right side, #2 and particularly #4 show signs of soot but are not wet. They look different from the rest. See the fotos below. I did an endoscopic examination inside the cylinders particularly #4 and #2. All the cylinders show moderate carbon build up on the top, nothing unexpected. I’m not sure what to think of the cylinder walls though. All still exhibit the cross hatching, however all have vertical scuffing to one extent or another. See photos below. Given the mileage I’m not sure what to think of the scuffing.

My current thought is that it has developed a stuck oil ring, probably in #4. Possibly from carbon coming loose. I’ve done 2 Seafoam treatments in the past and I currently run an anti carbon additive in the fuel. Today I started soaking all the cylinders in Marvel Mystery Oil. It’s the old school method to try and loosen a stuck ring.

So what am I missing here? The car idles and runs great! Compression is good. The PCV system is good. My only other thoughts are the IH gasket leaking oil from the breather to an intake valve. Possibly a head gasket? Both of those a low probability.

Your input is welcome...
H

#2 Spark Plug

#4 Spark Plug

#6 Spark Plug

#8 Spark Plug

#2 Cylinder top

Cylinder Walls

XfireZ51 · 02-20-2018

Hans,

Not sure if any of my experience applies but here’s the thread regarding what was found by Dr. Greekenstein.

http://www.zr1.net/forum/showthread....il+consumption

Ccmano · 02-20-2018

Quote:

Originally Posted by XfireZ51

Hans,

Not sure if any of my experience applies but here’s the thread regarding what was found by Dr. Greekenstein.

http://www.zr1.net/forum/showthread....il+consumption

I was thinking of your situation with the broken ring. Did you have good compression in that cylinder or was it low. Strange part on mine is the scuffing is in all cylinders and compression is good.
H

32valvesftw · 02-21-2018

Do cylinders 2 and 4 share the same coil? Maybe you have weak spark and incomplete combustion in those cylinders. The cylinders look ok as far as the hatch goes, but there is some minor scoring, no telling when that occured. Maybe oil starvation or overheating at some point in its life? I assume you did a static compression test? A leak down test may yield more information. Any lifter noises or seepage around the PCV piping?
Good luck with the Mystery oil. Does sound like a stuck oil ring at first glance, how high is oil consumption?

Paul Workman · 02-21-2018

Ccmano · 02-21-2018

Quote:

Originally Posted by 32valvesftw

Do cylinders 2 and 4 share the same coil? Maybe you have weak spark and incomplete combustion in those cylinders. The cylinders look ok as far as the hatch goes, but there is some minor scoring, no telling when that occured. Maybe oil starvation or overheating at some point in its life? I assume you did a static compression test? A leak down test may yield more information. Any lifter noises or seepage around the PCV piping?
Good luck with the Mystery oil. Does sound like a stuck oil ring at first glance, how high is oil consumption?

2 and 4 do not share a coil. The compression test was static with a warm engine. Since compression is not the issue I’m not sure a leak down test would provide any useful information. No lifter noises and no PCV seepage. Oil consumption is fairly high. A quart in 300-500 miles.

Good question. Keep the ideas coming guys...
H

gtcollins@maxnet.co.nz · 02-21-2018

Hi looks like oil sitting on top of the piston to the right

My engine will smoke if I decell hard from high rpm changing down the gears is this normal for LT5 engines

Sent from my SM-G930F using Tapatalk

Ccmano · 02-21-2018

Quote:

Originally Posted by gtcollins@maxnet.co.nz

Hi looks like oil sitting on top of the piston to the right

My engine will smoke if I decell hard from high rpm changing down the gears is this normal for LT5 engines

Sent from my SM-G930F using Tapatalk

I take it yours is the Black 90’. The 1990 came without valve stem seals. What you described is not unusual. I took the photos immediately after the compression test. I believe that’s fuel the piston.
H

gtcollins@maxnet.co.nz · 02-21-2018

Yes mine is the black 90 and I Will be rebuilding the original engine and will be fitting valve guide stem seals to the exhaust

Sent from my SM-G930F using Tapatalk

XfireZ51 · 02-21-2018

I discussed oil consumption with Marc recently. He stated that 1qt. per 700miles or so I not unusual. Now that doesn't mean you end up w sooty plugs.
But its pretty common to have oil puff showing after hard accel and decel. You can take a ZR-1 to the track and go thru a quart with just a few passes.

02-20-2018	#1
Ccmano Join Date: Jun 2006 Location: Sparks, NV Posts: 2,852	Oil Smoke - Input Needed Looking for some collective wisdom. Have to admit I’m a little stumped on this one. First some backgound. My car is an ultra high mile (181k) one owner 1990 car I bought last year as a long term restoration project. Although, the car is generally in outstanding condition. Some of you may remember the photos I posted. I’ve be working on her and have recently replace the transmission, clutch and flywheel (presenting their own issues). Also, adding headers and exhaust. Last year, the compression test was excellent averaging 190-195psi across all cylinders (I’m at 4500ft so add few more psi for sea level). It idles smooth and runs very strong. No signs of smoke of any kind other than when flogging her at full throttle. Even then just a hint of smoke which I consider normal for a 1990. I run Mobile 1 10w40 High Mileage oil. Dominic and I have been working since the first of the year tuning the engine for the current mods. The results have been outstanding. The car is responsive and strong. The weather here has been good allowing me to do several 40 mile data logging runs a week since then. The only issue has been an intermittent code 64 (right O2 Sensor lean) at idle after a long drive. Suddenly, about three weeks ago I started noticing light wisps of blue smoke accelerating lightly from a stop, only when the car is hot. This started to increase since then. I noticed it particularly on a long coast down in 4th gear coming down a long grade to a stop at the bottom. No smoke while coasting but when I accelerated away from the stop I got a good cloud. I’ve been monitoring it since and it is to the point where once the car is hot I get a good plume if I goose the throttle. There is no smoke at static idle though. There is no smoke at all while the engine is cold, even under acceleration. The smoke comes exclusively from the right exhaust. So I started looking at the usual suspects to try and find the cause. Valve guides are unlikely because they don’t fail suddenly like this and generally cause smoke at startup when cold. My car doesn’t do this. Next is the PCV system and the camcover breathers. Breathers are clean and generally dry. I removed the entire PCV system and found it to be in great shape with functioning PCV valves and no deterioration of the rubber pieces. All seals are good. I cleaned the PCV valves as a precaution. While there was oil in the system, there was not enough for concern. I even ran the car with the PCV system disconnected and still had the smoke. Related to the PCV system is excessive blow by caused worn rings. With the car idling there is no pressure or air being pushed out of either the oil cap opening in the cam cover or the dip stick tube. Nothing. Today I conducted another compression test, to my surprise it was better than last time. Averaging 200psi on the right side and 190psi on the left. Again, I’m at 4500ft, so add a few psi for sea level comparision. None of the cylinders stood out. I’m thinking the right left difference is timing chain stretch. Looking at the plugs, particularly the right side, #2 and particularly #4 show signs of soot but are not wet. They look different from the rest. See the fotos below. I did an endoscopic examination inside the cylinders particularly #4 and #2. All the cylinders show moderate carbon build up on the top, nothing unexpected. I’m not sure what to think of the cylinder walls though. All still exhibit the cross hatching, however all have vertical scuffing to one extent or another. See photos below. Given the mileage I’m not sure what to think of the scuffing. My current thought is that it has developed a stuck oil ring, probably in #4. Possibly from carbon coming loose. I’ve done 2 Seafoam treatments in the past and I currently run an anti carbon additive in the fuel. Today I started soaking all the cylinders in Marvel Mystery Oil. It’s the old school method to try and loosen a stuck ring. So what am I missing here? The car idles and runs great! Compression is good. The PCV system is good. My only other thoughts are the IH gasket leaking oil from the breather to an intake valve. Possibly a head gasket? Both of those a low probability. Your input is welcome... H #2 Spark Plug #4 Spark Plug #6 Spark Plug #8 Spark Plug #2 Cylinder top Cylinder Walls __________________ 90'ZR-1 #1461 Red/Black Ported Intake, Degreed Cams, OBX Headers & Exhaust, Fidanza FW, Secondary Delete, Custom tune, C6 GS Wheels. Sold 08 C6 Z51 Crystal Red Metallic Sold Vararam Intake, Tune, Sold 05 C6 Z51 Red/Black Sold 90'ZR-1 #1723 Black/Gray Sold but not forgotten 91' Z51 L98 White Vert. My First, you always remember your first. Sold. Last edited by Ccmano; 02-20-2018 at 09:18 PM.

02-21-2018	#5
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,493	Re: Oil Smoke - Input __________________ Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry

02-21-2018	#7
gtcollins@maxnet.co.nz Join Date: Mar 2015 Location: New Zealand Posts: 385	Re: Oil Smoke - Input Needed Hi looks like oil sitting on top of the piston to the right My engine will smoke if I decell hard from high rpm changing down the gears is this normal for LT5 engines Sent from my SM-G930F using Tapatalk

02-21-2018	#9
gtcollins@maxnet.co.nz Join Date: Mar 2015 Location: New Zealand Posts: 385	Re: Oil Smoke - Input Needed Yes mine is the black 90 and I Will be rebuilding the original engine and will be fitting valve guide stem seals to the exhaust Sent from my SM-G930F using Tapatalk

02-21-2018	#10
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,708	Re: Oil Smoke - Input I discussed oil consumption with Marc recently. He stated that 1qt. per 700miles or so I not unusual. Now that doesn't mean you end up w sooty plugs. But its pretty common to have oil puff showing after hard accel and decel. You can take a ZR-1 to the track and go thru a quart with just a few passes. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX

02-20-2018	#2
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,708	Re: Oil Smoke - Input Hans, Not sure if any of my experience applies but here’s the thread regarding what was found by Dr. Greekenstein. http://www.zr1.net/forum/showthread....il+consumption __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX

02-21-2018	#4
32valvesftw Join Date: Jun 2015 Location: Texas Posts: 530	Re: Oil Smoke - Input Do cylinders 2 and 4 share the same coil? Maybe you have weak spark and incomplete combustion in those cylinders. The cylinders look ok as far as the hatch goes, but there is some minor scoring, no telling when that occured. Maybe oil starvation or overheating at some point in its life? I assume you did a static compression test? A leak down test may yield more information. Any lifter noises or seepage around the PCV piping? Good luck with the Mystery oil. Does sound like a stuck oil ring at first glance, how high is oil consumption?