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on older engine--should convert to PCV valve setup?

3K views 10 replies 8 participants last post by  redsdad 
#1 ·
Besides spraying oil out of the breather pipe is there any advantage to converting to a PCV valve set-up?
 
#2 ·
yragat,

Not really. Some people say that the small amount of oil being mixed in with the air/fuel mixture lubes the upper cylinder walls. But if you have enough blow-by that oil is dripping onto the roadway then you may need more work than just a pcv up-grade.

Scholman(retired)
 
#8 ·
yragat,

You wanted to know what might need to be fixed to stop the blow-by.
Rings could be worn. Cylinders could have a large amount of taper causing compression to be lost past the rings.
Bad valve guides on the exhaust valves allowing hot gasses to be pushed into the engine. All not good.

Have Fun
Scholman(retired)
 
#10 ·
I acquired an old LeMans with a worn out 326 once. I liked the car with the 4 speed but it smoked something awful. Back in 74 Mobile oil had started selling it's Mobile 1 syn. oil and claimed a higher flash point being synthetic. So, I decided to experiment with it and at 5.00 a qt. (really high dollar back then)
I changed the oil and WALLA! no smoke. Only problem was it still used the same amount of oil at 5 bucks a qt. and it smelled like crap.
The cop's can cite you in California for excessive smoke but not for wasting money and grossing out everyone that follows you down the road. :D
 
#11 ·
yragat said:
Besides spraying oil out of the breather pipe is there any advantage to converting to a PCV valve set-up?
Do you mean the road draft tube? The one that exits the bottom of the car?

Run a compression test. If it comes out good, run a leak down test. If it comes out good, a PCV system will help you.

Here's why. All piston engines, no matter how well they are built, will have some blow-by past the rings. The blow-by collects in the crank case. At highway speeds, assuming it is not plugged up and you haven't altered the car in a way which will alter the air flow past the end of the road draft tube, the air passing over the end of the road draft tube will draw the blow-by out of the crankcase. Around town or idling, not so much. The blow-by will mix with moisture in the air and create acids in your oil. Results - sludge (or more frequent oil changes) and premature engine wear. A PCV system increases engine life because the "positive" in positive crankcase ventilation is just that; positive (and all the time).

If the engine fails a compression and/or leak down test, it probably doesn't matter.
 
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