LT5 Smoking on Startup

[Greatlandguy]

I have a 1991 ZR-1 with the first generation (375 HP) LT5 engine with 36,000 miles on it. I noticed now that upon starting, a significant amount of bluish white smoke emits from both tailpipes for a few seconds and then dissipates. It is not water vapor. No smoke has been observed when driving, though. Associated with this issue is a significant increase in oil usage, I calculated 1/2 quart per 600 miles.

Advice has been given that this could be worn valve guides or valve seals allowing oil into combustion chambers. Any thoughts on cause or diagnostics that can guide me to proper repair would be greatly appreciated!

[GOLDCYLON]

low miles but prob the valve seals and guides as stated since you stated the oil consumption as well. This is something normally confirmed after the tear down. GC

[Dynomite]

I would make sure the PCV system is working. Any oil in the corrugated intake/Air Horn?


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[Greatlandguy]

Thanks for the help, gentlemen. I will check the corrugated air intake and air horn for oil ASAP.

[Dynomite]

Marc Haibeck on oil consumption (http://www.zr1specialist.com/HAT%20Web/articles/my%20experience%20with%20LT5%20oil%20consumption.p df)

Seems you are average on oil consumption if you are driving it fairly hard. If you are just cruising then maybe a bit much on oil consumption. As an example, I just drove 2,000+ miles with 95' and did not use any oil. there was about 4 tablespoons of oil accumulated in my oil catch can ;)

http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite17/ba5010c3-1fa7-4e37-b571-3e4229d3b12c.jpg


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[FU]

Its normal for an early LT5. They didn't have exhaust oil seals.

[cvette98pacecar]

:cheers:

[Dime]

Its normal for an early LT5. They didn't have exhaust oil seals.

Just the 90s if I'm not mistaken.

[GOLDCYLON]

Just the 90s if I'm not mistaken.

Correct MY 90 only

[32valvesftw]

The OP did not state how long he has owned the car, so this may be a problem he inherited from the previous owner or a new problem that just surfaced. It would be good to know. I think he should do a compression leak down test. Checking the PCV system is good start IMHO, you might get lucky and avoid the leak down test.

[geezer]

Original injectors?? Ethanol ?? resulting in inj. leaking. More noticeable if car sits for a few days. Not evident if car used daily. Does the blue smoke appear on start-up if started on a daily basis?

[Hib Halverson]

If that engine is a 91, the duty cycle is primarily normal driving and not sustained high rpm use or track use, I'd say that a qt. ever 600 miles indicates a problem.

What kind of oil is in this engine?
What's been the drain interval?
PCV system working properly?
What to the spark plugs look like..all oily or only some oily?