Blue smoke?
Thread Starter
Instructor
Joined: Jun 2006
Posts: 125
Likes: 0
From: East Windsor CT
Blue smoke?
My 69 427/390 is blowing blue smoke (i know blue smoke is oil) out the left exhaust only and it is only at higher rpm (4k and above). It blows enough that I can see it on the highway. Ive only seen on it the highway when really goosing out in 4th gear and when in neutral in a parking lot. So I figured that either the rings or the valve seals have gone bad. I was leaning towards valve seals because that car sat for at least 3 years before I bought it. So last night I did a compression test hoping to see a cylinder that was far off from the other 7. Here are my results:
1 - 181 2 - 167
3 - 165 4 - 156
5 - 166 6 - 161
7 - 173 8 - 165
As you can see, none of the left bank cylinders are down in cracking compression. The first cylinder is a little higher but if 165 is considered as the norm (dont know if that is true or not but I went with a number that occured the most), then 181 is still within 10% of the others. Any ideas what could be causing my blue smoke? After I drive the car hard, some oil drippings can be seen on the valve covers near the breather and the oil cap. Thanks
Don
1 - 181 2 - 167
3 - 165 4 - 156
5 - 166 6 - 161
7 - 173 8 - 165
As you can see, none of the left bank cylinders are down in cracking compression. The first cylinder is a little higher but if 165 is considered as the norm (dont know if that is true or not but I went with a number that occured the most), then 181 is still within 10% of the others. Any ideas what could be causing my blue smoke? After I drive the car hard, some oil drippings can be seen on the valve covers near the breather and the oil cap. Thanks
Don
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
My first thoughts would be gummed up rings due to the sitting 3 years.I have brought many engines back by gently cleaning them up with frequent oil changes with high detergent oil.Here is one from Swepco there are others.
http://www.swepcousa.com/lubesite/oil.htm
http://www.swepcousa.com/lubesite/oil.htm
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
Originally Posted by DWncchs
My first thoughts would be gummed up rings due to the sitting 3 years.I have brought many engines back by gently cleaning them up with frequent oil changes with high detergent oil.Here is one from Swepco there are others.
http://www.swepcousa.com/lubesite/oil.htm
http://www.swepcousa.com/lubesite/oil.htm
try Marvel Mystery Oil its very light & does a good job cleaning. Run it until the smoke stops. If it doesn't after 200 miles chg & repeat. If the smoke doesn't stop you may have a bad ring.
1st Gear
Joined: Aug 2006
Posts: 1
Likes: 0
The valve seals are outside the compression chamber, so if the compression is normal chances are oil is getting past the seal, runs down the valve stem and when the intake opens sucks in the oil. the oil on the outside could be from an exhaust seal blowing exhaust back up into the valve covers, the pressure blowing the oil out the breather. My 79-350 sat for 3 years while I was in UK, smoked at startup and when I ran it hard. New valve stem seals at less than 12$ including valve cover gaskets did the trick....good luck. Jerry
Last edited by Chief_D; Sep 27, 2006 at 10:01 AM.
Thread Starter
Instructor
Joined: Jun 2006
Posts: 125
Likes: 0
From: East Windsor CT
Originally Posted by Chief_D
The valve seals are outside the compression chamber, so if the compression is normal chances are oil is getting past the seal, runs down the valve stem and when the intake opens sucks in the oil. the oil on the outside could be from an exhaust seal blowing exhaust back up into the valve covers, the pressure blowing the oil out the breather. My 79-350 sat for 3 years while I was in UK, smoked at startup and when I ran it hard. New valve stem seals at less than 12$ including valve cover gaskets did the trick....good luck. Jerry
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski