I'm trying to figure out, in all his wisdom, what Mr. T was thinking. I've been studying the Hot Air Intake and Hot Idle Compensation systems after I noticed my HAI diaphragm was always up - always feeding the engine hot air - no matter if the engine was hot or cold.
Before I go on: I'm in Denver and have to keep all my smog gear. My 60 runs great but I'm a meticulous guy and want to get to the bottom of this. I've also tested my HIC per the FSM and it absolutely works.
At cold conditions the middle nipple on the HIC is supposed to route vacuum from the PCV hose to the HAI and pull the diaphragm up. Great, some hot air off the manifold to help warm things up faster, a little feedback loop of heat. At hot conditions, however, the HIC is supposed to open up and allow the PCV vacuum to draw fresh air from the air cleaner in through the PCV hose to the base of the carb (bypassing the carb) to lean the mixture out a bit. Great, I guess, for emissions at idle when the heat of the motor is just sitting there. Photos of Emissions FSM below.
Here's where I'm stuck though. At all three levels of "hot" shown in the FSM, the diagram shows air coming OUT of the middle nipple TOWARDS the HAI diaphragm. This ought to keep it closed and let fresh/cold air into the air cleaner. This doesn't make sense to me though. Once the HIC is open, the PCV hose is providing the strongest vacuum (from where it originates at the base of the carb/manifold) - at the top of the HIC is a weak vacuum/atmosphere, and at the middle nipple you have a dead end at the diaphragm of the HAI. Of course the diaphragm is going to be sucked closed. See my hand-drawn diagrams.
So am I reading these two circuits wrong? Did Mr. T draw the diagrams in the FSM incorrectly or - gasp - design the circuit the wrong way? Is the engine supposed to just be drawing hot air all the time? i's love to hear some thoughts.
Before I go on: I'm in Denver and have to keep all my smog gear. My 60 runs great but I'm a meticulous guy and want to get to the bottom of this. I've also tested my HIC per the FSM and it absolutely works.
At cold conditions the middle nipple on the HIC is supposed to route vacuum from the PCV hose to the HAI and pull the diaphragm up. Great, some hot air off the manifold to help warm things up faster, a little feedback loop of heat. At hot conditions, however, the HIC is supposed to open up and allow the PCV vacuum to draw fresh air from the air cleaner in through the PCV hose to the base of the carb (bypassing the carb) to lean the mixture out a bit. Great, I guess, for emissions at idle when the heat of the motor is just sitting there. Photos of Emissions FSM below.
Here's where I'm stuck though. At all three levels of "hot" shown in the FSM, the diagram shows air coming OUT of the middle nipple TOWARDS the HAI diaphragm. This ought to keep it closed and let fresh/cold air into the air cleaner. This doesn't make sense to me though. Once the HIC is open, the PCV hose is providing the strongest vacuum (from where it originates at the base of the carb/manifold) - at the top of the HIC is a weak vacuum/atmosphere, and at the middle nipple you have a dead end at the diaphragm of the HAI. Of course the diaphragm is going to be sucked closed. See my hand-drawn diagrams.
So am I reading these two circuits wrong? Did Mr. T draw the diagrams in the FSM incorrectly or - gasp - design the circuit the wrong way? Is the engine supposed to just be drawing hot air all the time? i's love to hear some thoughts.