I have a 68 200 cu in 6 cyl 3-speed auto. The carb currently only has a gasket between the base and engine. I have a metal spacer that also fits this, which you have to connect a heater hose to. I understand the purpose of this type spacer is to speed up the heating up of the choke spring. Is that correct? Is this type spacer actually needed? The car runs fine without it.

 

Has nothing to do with the choke. The hot water tube prevents carb icing, which can occur under certain weather conditions, between roughly 30°F and 80°F. The engine will lose power, and even stall if this occurs. This condition is also why 6 cylinder car had a rubber flap at the top of the radiator support.

 

Can you elaborate on this rubber flap you're talking about?

 

I fail to see how icing can occur at 80* under any weather conditions...maybe below 30*.

 

I'm guessing you're not a pilot. Below 30°, there is not enough humidity to cause icing. Remember, the engine sucks air/fuel into the engine, causing manifold vacuum. When the air is humid, this water vapor condenses as the air expands and cools. Sometimes, when conditions are favorable, it cools enough to freeze in the intake manifold. This can cause your car to run poorly. It will cause your plane to crash, killing you. The six cylinder uses a water-heated spacer to prevent this. Some 390's, including the 69 Mustang 390, also had a heater spacer. Usually, as in the case of most smallblocks, the exhaust passage below the carb did the job.

The rubber flap directed intake air through the radiator, heating it more than if it passed over the radiator. The 67-70 390/428 cars used the same flap. Here you see the flap stapled to the rad support.

 

Looking at your photo, which hose goes to the spacer - right or left?

 

 

Thanks very much!