PF 25 oil filter

Chevyforever

Veteran Member
Jan 4, 2011
1,443
Ontario, Canada
Gravity likes to pull the oil into the oil pan when the engine is not running. Engines using a cam-in-block arrangement, having oil in the upper galleys during startup is critical to the life of the engine. If the oil is not there, camshaft bearings can wear along with the lobe and lifter. What keeps the oil in the upper oil galleys is the anti-drain back valve. It protects against the backflow after the engine is turned off. I have used filters with and without ADBV for years , however I do believe there is value in those containing the ADBV on the Chevy V8.
 
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Gary S

Administrator
Lifetime Gold Member
Apr 14, 1999
24,520
Bismarck, North Dakota
Think back people. Have you ever changed oil on an old small block Chevy engine and had the filter anything than overflowing full even if the engine sat for years without being started? Every filter I've removed in 50+ years has been full to overflowing as soon as the filter is loosened. That tells you that the anti-drain back valve is useless and possibly harmful if it chooses to limit oil flow to the engine.

Look into the top of a filter with anti-drain back valve and you can see the valve. The valve is nothing more than a "flap" of plastic blocking the filter. When the engine has oil pressure, it lifts the flap so oil can flow around it. I don't want anything like that between my engine and oil pump. A filter without the valve is fully open to oil flow. That is my way of doing things.
 
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kenny77

Veteran Member
Lifetime Gold Member
Jul 31, 2001
3,276
Ft. Lauderdale, FL
In all my small block books, no place is an anti drain back filter ever mentioned or shown in the factory drawings. It was designed at the very start to hold oil, I mean look at the position of it. Anti drain back was invented by mfgs that put the filter sideways on the engine. And that was DECADES after the Small Block Chevy was designed. No vertical filter would need one. Common sense.
 

Chevyforever

Veteran Member
Jan 4, 2011
1,443
Ontario, Canada
In all my small block books, no place is an anti drain back filter ever mentioned or shown in the factory drawings. It was designed at the very start to hold oil, I mean look at the position of it. Anti drain back was invented by mfgs that put the filter sideways on the engine. And that was DECADES after the Small Block Chevy was designed. No vertical filter would need one. Common sense.
Just checked the CT350 "602" Chevy Crate Engine instruction booklet I have (~28 pgs) and in the break in procedure section it states " Change the oil and filter with 15w50 full synthetic motor oil and Ac Delco PF454 (P/N 25324052).
Hmm ... good thing those engines aren't constantly pushed to the limit and beaten up under gruelling conditions for entire race seasons. Chevrolet Performance lacking "common sense" I guess.
 




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