PCV system
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| + | ==Why do we need PCV Valves== | ||
| + | Positive Crank Case ventilation is needed to help remove the acidic gaseous buildup inside the crank case. This is caused by combustion gas blowby around the rings as well as fumes released as the oil gets hot. | ||
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| + | ==History== | ||
| + | Before the PCV system road draft tubes were used. This basically vented the gasses directly to the atmosphere. This was major source of smog in big cities and an initiative was launched to solve this. GM invented the PCV system and "gave" it to other manufacturers to use. This was the first emissions control device on automobiles and it drastically reduced the smog problem. | ||
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| + | ==Typical Configuration and Components== | ||
| + | There are only a few components involved in the PCV system. | ||
| + | * A breather is located in the passenger side valve cover through a rubber grommet. This allows fresh air to enter the engine. There are two popular ways to do this. | ||
| + | ** A tube that connects to the valve cover to the air filter. | ||
| + | ** A small air filter that pushes directly on the valve cover. | ||
| + | * The PCV valve itself is located on top of the driver's side valve cover through a rubber grommet. | ||
| + | ** The area inside the valve cover where the grommet is located should be baffled. This helps to avoid oil getting sucked into the valve. | ||
| + | * A rubber hose that connects the PCV valve to the intake or carb (or some sort of vacuum source to be digested into the engine). | ||
| + | * This setup allows fresh air to enter one side of the engine, go through crank case, and exit out the other side. | ||
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| + | You should avoid attaching the breather tube and PCV to the same valve cover. This will not vent any of the combustion gases. | ||
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==PCV valves for modified engines== | ==PCV valves for modified engines== | ||
Big cams with low idle vacuum throw can throw off a stock PCV valve, creating a lean idle. Normally at idle the PCV is in the low flow position. But if the PCV valve is open at idle (because of low idle manifold vacuum caused by a big cam), the idle gets lean and unstable and may suck too much oil along with too much air. This is akin to a big vacuum leak at idle because the PCV is open at idle instead of in the idle (low flow) position. | Big cams with low idle vacuum throw can throw off a stock PCV valve, creating a lean idle. Normally at idle the PCV is in the low flow position. But if the PCV valve is open at idle (because of low idle manifold vacuum caused by a big cam), the idle gets lean and unstable and may suck too much oil along with too much air. This is akin to a big vacuum leak at idle because the PCV is open at idle instead of in the idle (low flow) position. | ||
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