Chevrolet Repair: variation in vacuum under load, monte carlo ss, engine vacuum

Question
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Followup To
Question -
I have a 1984 Monte Carlo SS(305 v8). When the engine is warm the pcv valve will rattle ( approx. 5-10 times per second) when I press on the accelerator. I assume that the engine vacuum is varying but I don't know what is causing the variation. I have replaced the pcv valve, the canister control valve and the thermal vacuum switch. The problem  must be in some other vacuum line or device.All of the vacuum lines look ok. Could  the front break vacuum switch on the carb.(or some other vacuum switch) be causing the problem or is this an internal engine problem?
Answer -
Hi Dave, The first thing you to do is get a AC delco PCV valve. I know that the aftermarket valves will do this.

Hope this helps
I do have an Ac Delco valve. The problem is with the engine vacuum, not the pcv valve.
Mark

Answer
Sorry Dave I just have seen sooo many people with the aftermarket valves. If your manifold vacuum is changing that fast then you must have a camshaft lobe gone bad or a lifter that is sticking. You need to remove the valve covers and see which rocker arms isn't moving like the rest.

Mark