today i have put that small spoiler underneath (radiator)... although i was told i didn't realize that it could make such a different... my estimate  temp got down by atleast 20degree F..

It's not just directing air up to the radiator (though it's the prime reason), the spoiler also keeps as much air as possible from passing under the car creating drag and turbulence, which requires more power to overcome.

I agree. I've had cars in my shop with similiar small grilles overheat going down the road. Any car with such small amount of air going through the grille need all the help they can get. Espically when running the air. The spoiler made all the difference. Terry

I never knew the spoiler helped the cooling affect of the car!! Learn something new every day....

That's the main reason it is there. When the '68 cars were being developed, they couldn't keep the engine temps down, so they put on a small spoiler...that helped, but what really did the trick was Zora going under there and cutting the 3 holes out of the lower valance panel in front of the spoiler. This allowed the spoiler to direct the airflow directly over(thru) the radiator, increasing the cooling effect. The first '68 cars had these holes cut with saws...not very pretty. Without the holes in the valance, the spoiler contributes very little to the cooling.
Without the spoiler, the air pretty much just passes under the car, and doesn't go thru the radiator.

Can anyone tell me the exact part name of this spoiler that goes under the radiator? I think I may need one for my '74. Who sells it?

It's called an "Air Dam"
Most Vette suppliers have them...normally around $40 or so.

from what i have read and even though i am installing electric fans, i will be installing a new air dam on mine. have read with the fans seals aren't as important but if i can reduce the wear and tear on fans i will.