Blow By
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Joined: Jan 2008
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Blow By
What causes it ?
Worn out Compression and Oil, Piston Rings.
The valves are sealing but the rings are shot so,the compression and exploded gases are BLOWN by the rings into the crankcase and forced up to the top of the engine out the valve cover(through the PCV valve)rather than staying in the cylinder and exiting out the exhaust.
How to fix it ?
Rebuild the whole engine !
https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=768&.jpg
Dennis
Please Don't Ask Me Any Tough Questions As:
"I'm Saving Up MY Memory For When I Develop Alzheimer's"
78 F-150 429CJ C6 ,Silver w/Explorer Pkge
641/2 Mustang,Pre-World's Fair Car #8092
64 Fairlane S/C waiting for a 390-4spd.
68-Mustang.Sunlit Gold 80,000 miles
Worn out Compression and Oil, Piston Rings.
The valves are sealing but the rings are shot so,the compression and exploded gases are BLOWN by the rings into the crankcase and forced up to the top of the engine out the valve cover(through the PCV valve)rather than staying in the cylinder and exiting out the exhaust.
How to fix it ?
Rebuild the whole engine !
https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=768&.jpg
Dennis
Please Don't Ask Me Any Tough Questions As:
"I'm Saving Up MY Memory For When I Develop Alzheimer's"
78 F-150 429CJ C6 ,Silver w/Explorer Pkge
641/2 Mustang,Pre-World's Fair Car #8092
64 Fairlane S/C waiting for a 390-4spd.
68-Mustang.Sunlit Gold 80,000 miles
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Joined: Dec 2001
Posts: 22,436
Likes: 17
From: Louisville,Ky.
Blow By
Yes weak rings or scarred cylinder walls or even a cracked piston can cause it. If it is excessive, then a rebuild is in order. You may want to check your PCV valve to see if it is working properly. It should rattle when you shake it(engine off). With the engine running, pull it out of the valvecover and stick your finger over the hole in the valve and it should suck your finger to it. If not, either the valve is bad or or your line is clogged. I have seen them clog up after years of service. Also check where the hose connects under the carb and make sure that it is not gummed up. A small amount of blowby is acceptable on a high mileage engine, but it shouldn't be more than the pcv valve can handle to keep any from escaping into your air cleaner( or the other valvecover hole if you don't have a hose going to your aircleaner) 
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