One of the genius POs of my '79 F150 decided to bypass a 4 port vacuum switch and throw out the spark delay valve which allows a limited amount of vacuum to reach the distributor during warmup. I need to get that part, but no parts vendors sell them. Its basically just a piece of plastic with a small hole in it, so I figure the main jet for a small engine would be perfect. I could dial in the desired vacuum level by drilling out the jet. Does anyone know what thread size the jets are?