11-25-2006, 12:53 PM
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CC Member
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Join Date: Dec 2000
Location: Austin, TX, US,
TX
Cobra Make, Engine: Exact427
Posts: 70
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Positive Crankcase Ventilation - Another Option
A different PCV approach was utilized on some engines during the 70's.
The most common method uses a PCV valve attached between the crankcase and the intake vacuum. Fresh air is provided via a separate breather cap (usually oil filler) on early cars, while later models ran a hose to the air cleaner to use filtered air. This air flow loop seems most effective right to left in the valve covers but obviously works front to rear as well. As an open system, it would have no vacuum.
Another method you'll see doesn't use a PCV, but connects the crankcase via valve cover directly to the intake vacuum. There is NO beather or fresh air. This works as a sealed system and I'm guessing actually provides a vacuum to the crankcase.
1. Is the breather really necessary? Pros/Cons?
2. Modern drag racers run vacuum pumps, can the alternate method improve performance?
3. One manufacturer switched from a PCV valve system to a sealed PCV system DURING the production run. (engineering improvement?)
4. Anyone ever try the "ALTERNATE" system for PCV? Dyno results?
Last edited by Roger Bolick; 11-25-2006 at 01:54 PM..
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