My car used to be injected, the previous owner threw a new manifold and a carb on the car. The air cleaner vacuum hose, and the pre heated hose were never there. Would it be a good idea to get those on the air cleaner? Even though it isnt injected anymore?

 

It was used so the factory could tune the carbs to be more emissions-friendly. Most q-jets work better with it. It operates until the engine warms up (except in extremely cold weather, when it may stay open). I know with factory q-jets, it could get downright scary when the engine had only been running a couple of minutes and the choke was starting to open, it could lean out and stumble pretty badly if that tube wasn't there.

If you have a Holley or Edelbrock carb, there's a good chance you can get by without it.

 

It was first used in the 60s, long before EFI was even dreamt of. So yeah...

Where you are (TX) it probably doesn't get cold enough to be critical; but cars usually run better in cold weather WITH it.

 

That is called the Thermac system in GM nomenclature. It's purpose is to ALWAYS deliver at least 100*F air into the carb by mixing hot air from the heat stove and cold air from the regular snorkel opening. There is a thermal vacuum switch built into the base of factory GM air cleaners to modify the amount of vacuum sent to the "flapper door servo" on the snorkel for this reason- to get the proper mix of hot and cold air to make it 100*F inside the air cleaner.

It serves TWO purposes, actually, neither of which probably matters to you, but definitely matters on factory vehicles.....

1. It is to help with emissions. Carbs do a better job supplying a consistent A/F ratio if the intake temp is held constant. Carbs can't compensate for air temp changes very well. It's not a big difference, but when you have to pass Gov't emissions testing like the OEMs do, every little bit helps.

2. The REAL reason. Preventing carburetor icing. This is a phenomenon that happens between about 30* and 50*F. Any moisture in the air (humidity) will condense on cold parts, much like fogging a mirror. This is not a problem unless the part they condense onto is COLDER than 32*F. Then that condensation turns instantly to ice. The throttle plates on a carburetor get VERY cold due to the fuel being atomized and evaporated in their vicinity (evaporation is a cooling process, if you remember high school physics). When there is sufficient moisture in the air and temps are within spitting distance of freezing the throttle plates can start to get a buildup of ice on them! This buildup slowly starts to choke off the airflow past them, especially at idle when the throttle opening is very very small. Idle speed goes lower and lower and lower as more and more ice builds up. The engine can actually stall in extreme situations! And this phenomenon will persist until either the air going through the carb gets warm enough to stop it or engine heat penetrates into the carb and makes the throttle plates too warm to allow ice to form.

It takes a LONG time for engine heat to conduct up into the carb. Heating the incoming air can be done MUCH faster with the Thermac (intake air heating) system. Which is the main reason why it existed even before the "emissions era" of the 1970s.

Do you need this on your modified vehicle? No. Not unless you daily drive in cooler weather. Then it can be handy. But even on a daily driver, you can just feather the throttle a little on cold mornings until the carb and intake heat up enough to prevent carburetor icing. In short, it's no biggie.

 

BTW- howdy, five7 and sofa. I know we often see eachother around in threads on this board but it's rare you get all three of us right in a row!

 

In texas now it is realllly cold, my cars not doing too good in the mornings