I apologize to bump this old thread, but I was researching how to tell whether my secondary was opening or not, as I felt that it wasn't. This paperclip trick is ingenious! So, I put the paperclip on, and went out to the pavement, and floored it up a hill. WOT on a medium grade in 4th gear. If the paperclip moved at all it wasn't by much:
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So, I think I should replace that secondary diaphragm, the Walker rebuild kit I used didn't have one. What is the best source for that part, I believe it to be NLA from Toyota? When I had it apart, that diaphragm held water, that was the best test I could think of for it... so maybe there are other problems? I put my vacuum gauge on the distributor port on the other side of the carburetor and verified vacuum when I revved the engine. Also on manifold vacuum I am sitting at 19 now that I replaced my leaky old break booster. Any advise is greatly appreciated!