PCV system on a Mustang 1965 1966

Lately, I've had several people ask me about this system, how it works, what is it's purpose, etc...so, here's how that works and why it's important. As the fuel is burned in the combustion chambers of an internal combustion engine, the motor does not burn 100% of the fuel. Most of that unburnt fuel goes out the exhaust, but, some goes past the piston rings down into the crankcase. Also, all of the exhaust gases don't go out the exhaust. Some of that also gets past the piston rings, and again, ends up in the crankcase. As one might imagine, having these combustible gases hanging around in the oil pan can't be a good thing. What they actually do is contaminate the oil, degrade the lubricating qualities of the oil, and cause your motor to wear out a lot quicker than it should. That is with a motor in which everything is as it should be. In a motor that is getting a little tired and has excessive ring clearance, this problem is multiplied and the gases can accumulate quickly enough to actually catch on fire in the crankcase. People have devised different ways of dealing with this problem over the years, but, we'll stick to Ford's solutions. In the Model B Fords, the first cars that had the flathead V8s in them, the solution was very simple. Ford put a hole in the front of the oil pan up near the top and welded a flap in front of it to keep rocks and stuff from bouncing into the oil pan. A very straight-forward idea, but, one that cried out for some modifications. They later developed what was called a road draft tube, which you can find on some of the 64 1/2 Mustangs. This was the same idea, basically a hole to let air in through, but, a hole that road crud couldn't really find it's way through. However, dusty crud could still get sucked in.Next was the positive crankcase ventilation, or, PCV, system. Vacuum is generated by the pistons, so, they put a hose from the base of the carb over to one of the valve covers. The gases that blew by the pistons and wandered into the crankcase get sucked back into the combustion chambers. To solve the problem of the massive vacuum build-up this creates, they put a vented oil filler cap on a hole in the other valve cover. This allows fresh air to circulate through the motor and prevents the build up of the blow-by gases. They put a one-way valve on the hose that goes to the carb to prevent air/fuel mixture from going the wrong way.

A good and useful system, and very easily maintained. All one has to do is clean out the filter in the oilfiller cap to keep it from getting clogged up, and clean the PCV valve occasionally to keep it from getting stuck.