Later F134 4 cylinder engines used PCV valves as opposed to the breather mechanism shown in the 1965 factory service manual. Below is a basic diagram of the F134 that uses a PCV valve:
One of the problems I found on my engine was a previous “repair” that had rendered the PCV valve inoperative. A 3″ long wood screw had been driven into the brass “L” fitting to plug a hole, jamming the PCV in the process. The valve was not able to open enough to let the engine “breathe,” but it was also always “open” enough to create a permanent vacuum leak at idle.
Removing the screw and plugging the hole properly fixed the sludge buildup problems I had as well as curing the permanent vacuum leak as well.
Below is a diagram of how a PCV valve works:
A working vacuum and PCV system is critical for proper engine performance, proper vacuum wiper performance, and preventing engine sludge buildup.