Always stick to the basics, no short cuts....!!!!!

[Wigert]

Originally Posted by Ccmano

With only 7700 miles I seriously doubt you have the same issue. With mileage that low I wonder if the rings have properly seated. I would do a compression and leak down test.
H

I seem to gave missed a digit, My Z has 77000 miles. What is considered high mile for a Z?

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[Ccmano]

Originally Posted by 5ABI VT

wow thanks for sharing. Very interesting I wonder if this may have been the issue with many cars I have seen threads about oil consumption etc. What did the plugs look like?

The plugs did show signs of oil burning, not wet, but numbers 2, 4 and 7 were discolored. All this came on rather suddenly while I was doing datalogging runs after a header install. Based on what I know of the cars history I suspect it was rather meekly driven most of its life. Me driving it more aggressively likely loosened the now hard gaskets because of the loose IH bolts. At least that’s my theory.
H

[Ccmano]

Originally Posted by Wigert

I seem to gave missed a digit, My Z has 77000 miles. What is considered high mile for a Z?

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77000 is generally not that high but does make this condition more likely. Rings will definitely be seated with that mileage and more likely not your issue. The higher the miles the more heat and vibration cycles the engine has endured. Add to that age and things like loosening bolts, hardening gaskets and brittle plastic happens.

Pull your plugs and try to identify which cylinders are most affected. A compression and leak down test will tell you if rings or valve guides are a problem. At idle remove the oil fill cap and check for air blowing out of the cam cover, there should be none. Blowing air indicates a ring problem. Check the pcv system for functionality. Run the car with the PCV system open to atmosphere for the same time you have experienced the oil consumption. (Cap the vacuum line to the plenum) If oil consumption stops, this will tell you if oil is being sucked through the PCV system. If all this comes up negative your are left with only three other possibilities. Oil ring collapse, head gasket failure (although that usually manifests in others ways too) and my issue of IH gasket failure. This is where I made my error. I jumped to the oil ring collapse conclusion and never checked IH gaskets first.

Having said all that it is my understanding that some engines simply don’t like to be at full oil level. They consume the first quart and then stabilize at one quart low burning no more oil. Apparently a windage issue but not harmful. Try letting the engine get a quart low and see if it stops there.

There are more exotic possibilities but they generally require a tear down anyway. Follow the basics above and it will take you to the source of the problem.
H

[Wigert]

Originally Posted by Ccmano

77000 is generally not that high but does make this condition more likely. Rings will definitely be seated with that mileage and more likely not your issue. The higher the miles the more heat and vibration cycles the engine has endured. Add to that age and things like loosening bolts, hardening gaskets and brittle plastic happens.

Pull your plugs and try to identify which cylinders are most affected. A compression and leak down test will tell you if rings or valve guides are a problem. At idle remove the oil fill cap and check for air blowing out of the cam cover, there should be none. Blowing air indicates a ring problem. Check the pcv system for functionality. Run the car with the PCV system open to atmosphere for the same time you have experienced the oil consumption. (Cap the vacuum line to the plenum) If oil consumption stops, this will tell you if oil is being sucked through the PCV system. If all this comes up negative your are left with only three other possibilities. Oil ring collapse, head gasket failure (although that usually manifests in others ways too) and my issue of IH gasket failure. This is where I made my error. I jumped to the oil ring collapse conclusion and never checked IH gaskets first.

Having said all that it is my understanding that some engines simply don’t like to be at full oil level. They consume the first quart and then stabilize at one quart low burning no more oil. Apparently a windage issue but not harmful. Try letting the engine get a quart low and see if it stops there.

There are more exotic possibilities but they generally require a tear down anyway. Follow the basics above and it will take you to the source of the problem.
H

Thanks for the great writeup, I really appreciate it! This forum is a goldmine. I really have a lot to learn here and now several things to investigate. I hope that I am not in for a rebuild...



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[G-Sting]

I also sure appreciate this thread, H. Mistakes, shortcuts - we've all done them. Hopefully, not as a habit, of course. But a job done methodically, correctly and thoroughly the first time... almost always works out best.

But now you have an extra LT5 for your mantel. ...or install it in an old Porsche 911.

Thanks again for sharing your experiences and expertise.
G

[LGAFF]

Just don’t make a 2nd mistake by telling your wife


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[Ccmano]

Originally Posted by LGAFF

Just don’t make a 2nd mistake by telling your wife


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Learned to not make that one a long time ago....
H

[gtcollins@maxnet.co.nz]

Thanks for your honesty we have all made mistakes hopefully others can learn from your experience last night I was driving my ZR-1 and pulled up at the lights after down changing and was waiting for the lights to change and was looking out my side window and sore a lot of smoke go by I just topped the oil up if you watched the video I did there was on smoke on decel so maybe I need to burn of the top 1 liter there are other vehicle that do the same

Regards Glen

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[A26B]

Originally Posted by gtcollins@maxnet.co.nz

Thanks for your honesty we have all made mistakes hopefully others can learn from your experience last night I was driving my ZR-1 and pulled up at the lights after down changing and was waiting for the lights to change and was looking out my side window and sore a lot of smoke go by I just topped the oil up if you watched the video I did there was on smoke on decel so maybe I need to burn of the top 1 liter there are other vehicle that do the same

Regards Glen

Glen,
My apology if you already are aware of this;
The LT5 is notorious for slow oil drain-back to the oil pan from the top end after shutdown.

I noticed that you mentioned "just topped the oil up". If you did this based on the dipstick reading after turning the engine off, it is highly probable that you have overfilled. The best time to check oil level in an LT5 is the first cold start of the day.

[gtcollins@maxnet.co.nz]

Thanks Jerry yes I always check in the morning before start up

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