[Sam Mac]

That is not factory. That is something a previous owner added. If I had to bet my guess is that it has a bad head gasket and that the PO added that to try to direct the blow by away from the air filter. Vanguards do not tolerate over heating very well. Plan on pulling the engine out, removing the blower housing and tins and giving it a good cleaning. You'll probably find the cooling fins plugged up. What I do to test an engine to see if it has a bad head gasket is to pull the valve cover, remove the push rods and spark plug then I hook up an adapter so that I can use my shop air to pressurize the cylinder. If you have a bad head gasket or piston problem you'll hear air escaping into the the push rod area or oil return, a bad exhaust valve and air will come out the exhaust, bad intake and the air comes out the intake. This one puke the head gasket and it blew into the oil return.