I have a Holley 4160 390CFM 4bbl carb with vacuum secondaries on my 1959 Ford 292 Y Block standard shift vehicle. I started the engine and the engine had it's usual curb idle of about 750 RPM. There is an inline filter at the carb and a filter mounted at the gas tank before the electric fuel pump. Then, I shut it off and added some antifreeze. Restarted the engine and now the engine won't idle unless the curb idle is around 1100 RPM. I did not do anything else to the engine and never touched the carb. I don't think the anti-freeze has any bearing on the problem. I don't want to start taking the carb apart without first having some idea about what might be causing the problem. The carb is about 10 years old and has always run great both at curb idle and on the road. Any suggestions and info. are very much appreciated. Thanks.