There are a few basic tests for the PCV system that can be performed to get an idea if the system functions and has enough flow. First, the better your ring seal, the less need for crankcase ventilation. The PCV valve itself is a simple, yet very carefully engineered "shuttle type" flow control valve. The taper of the pintle inside, the spring wire size and spring rate, and the orifice size on both sides of the valve all contribute to the flow character of the valve. The valve shuttles in it's housing passing blowby gasses based on engine vacuum. If the engine makes 15" or more vacuum at idle, the correct stock PCV valve will work fine. If the engine has a hotter cam, gently raise the engine RPM to 1200 RPM. If you have 15" of vacuum at 1200, you will still be OK with stock system. If you have a really hot cam and are driving on the street, you really need a vacuum pump. Possibly, the adjustable valve mentioned in the thread would be a benefit on an engine making 10" of less vacuum at idle. Couple of other simple tests you can do. Pull out the pcv valve with the engine running and put your thumb over the end of the valve. You should get a 50-100 RPM drop as you do this. No drop, the PCV valve is not flowing much if at all at idle due to incorrect valve or very high vacuum. More than 100 RPM drop, the valve is passing too much at idle and can begin to use oil, smell like burning oil, smoke, idle rough or high. The single most common problem on restored or old muscle cars PCV systems is the hose from the valve to the engine. That hose from the factory is a molded or reinforced hose. When replaced, regular 3/8" fuel hose is often used. IT WILL SUCK SHUT easily and the system will no longer work. If a molded hose is not available, use power steering return line for the PCV hose and make sure it has no tight bends. Another test is to buy or find a heating and AC guy who had a water manometer, sometimes called a slack tube. It is a simple water low pressure gauge. Put the manometer hose tightly sealed to the dipstick tube. At idle, the engine should have a minimum of 1" of water. 1-5" of water is the range you want at idle. A final simple test that is much more fum is to take your Pontiac out and run the crap out of it. Make several runs wide open to the red line. Now open the hood and look at the dipstick. You have a PCV problem if the dipstick is pushed-up out of the tube, like a pencil tire gauge. If you don't see or smell any oil, the dipstick is firmly in the tube, the engine idles smooth, save your $129.00. Not saying the part described is stupid or overpriced, but only a very tiny % of street engines need or would benefit from it in my opinion.
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