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Old 08-01-2002, 11:39 AM
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I am having a lot of blow-by coming out of the valve covers and the dip stick on my 350. It does not have a pcv system. There is a hose and a filter in the aircleaner that pulls air out of the block. I have flipped the cover of the aircleaner over to get more air to the motor so I am not sure how effective this system is.

Why am I getting so much blow-by and how can I solve it?
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Old 08-01-2002, 02:03 PM
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[quote]There is a hose and a filter in the aircleaner that pulls air out of the block.<hr></blockquote>

You have to have some type of crankcase ventilation system. The hose you are describing is the fresh air inlet for a PCV system. You need to have a PCV valve on the opposite rocker arm cover and a manifold vacuum source to operate it.
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Old 08-01-2002, 02:10 PM
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Blow by comes from one thing and one thing only, Bad Piston Rings, you will need a rebiuld the motor to fix the problem entirely.run a compression test on the motor and let me know how it goes, be sure to record the info for each cylinder. after the first reading try sqiurting in some engine oil had recored the results.
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Old 08-01-2002, 02:28 PM
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All engines produce some blow-by, if they didn't manufactures wouldn't have invented systems to deal with it. Piston rings do not seal 100%. you need a pcv (positive crankcase ventilation) valve in one valve cover connected to manifold vacuum. This applies a controlled vacuum source to the crankcase. The fresh air is drawn in the other valve cover. Theat's what the crankcase filter is for (that's the little filter in your air cleaner). Fresh air through filter, into valve cover, through engine crankcase, sucked out by pcv in other valve cover, into intake to mix with intake charge. We used to just have breathers in both valve covers untill the gov't said it was illegal to vent crankcase vapors (blow-by) into the atmosphere. That's when they came up with the pcv system. You should also make sure you have baffle plates under the holes in the valve covers to prevent the pvc from sucking oil out of the valve cover. Adding a pcv system to your engine should correct the problem unless your engine is really spent but to expect no blow-by in an engine without a pcv system is rediculous.
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Old 08-01-2002, 02:47 PM
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Thanks for the help. I guess I had it working backwords. I figured the gases would get sucked into the carb thru the hose and filter. Sometimes the simplist and most obvious things are overlooked. There is no hole in the other valve cover for a pcv valve. I will have to find another valve cover so that I can install the pcv.

Back to the junk yard for parts I suppose.

Thanks again.
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