[StealthBird]

In the F.A.S.T. Series, the 68-69 Vettes benefit more from their lightweight and aerodynamics than from their air induction. At speeds over 100 mph, wings, dams, and other aero devices start to play a significant role. A front spoiler on a 69 Camaro is good for a mph in the traps with a car hitting 100 mph.

The various cold air setups didn't provide any actual ram effect, with the exception of the car traveling in excess of 100 mph, and even then only a few setups were capable of providing a VERY minor amount of positive pressure. The factory setups were not very efficient, more for show than go. But they did draw in cold air, and they worked. Various marketing tactics made the buyers believe that ram air would make your car a street terror, and some manufacturers came up with outrageous claims. In reality, adding a cold air intake setup, and jetting accordingly, was what made the ram air setups effective.

Why didn't everyone just use a hood scoop? Well, plenum or cowl setups were preferred because many manufacturers didn't want to use a hood scoop. Hood scoops were considered boy-racer stuff, not to mention the fact that hood scoops were warranty nightmares when owners drove year round, through torrential rain, blizzards, etc.

A12 Mopars used a huge scoop, but keep in mind that they still weren't directly in the airstream. Much larger and bolder than the other manufacturers, yes, but at over 100 mph the air would be pushed up and over the scoop. It was a far more effective setup than the GTO scoops of the era, but still far from ideal. Mopar wanted the drag racer look, so they had no problem making their scoops visible. And when they weren't visible, they had a switch that raised the scoop. [img]<<GRAEMLIN_URL>>/naughty.gif[/img]

In order to create ANY positive pressure at high speeds, the scoop(s) need to be at the leading edge of the hood, and have a straight path to the carb. Lots of examples of great scoop design, which made for great marketing, but the setups had little chance of producing any ramming effect.

The 66-69 Olds OAI setup had the right idea. However, the duct work required under the hood caused a loss of ramming effect. For every turn or bump in the ducting, pressure is lost. While they did bring in cool air, they didn't provide any ramming effect. Olds switched to the 70-72 OAI setup because it was more aggressive looking, and met their marketing tactics of getting their Oldsmobiles noticed at stoplights.

The 1969 Trans Am also had the right idea, the first GM car to have functional scoops placed at the leading edge of the hood. Unfortunately, that setup was suffocated by a small air filter.

The 1970-1975 Formula hood had the scoops in an even better location than the 1969 Trans Am, but the 90 degree turns from the plenum to the air cleaner, and 90 degrees again to the carb, killed any possibility of a ramming effect.

Shaker scoops were visual and provided cool air, but no ramming effect. The design of the 1970 Trans Am shaker was flawed, with the scoop placed too far forward to get any benefit from the high pressure buildup at the base of the windshield. They wanted to extend the scoop backwards, but styling overrode engineering. The shaker was basically a door to cool air.

Cowl or plenum induction works well at getting cool air. There's isn't enough pressure buildup at the base of the windshield to provide any ram effect, but the cowl is an excellent source of cool air. No bugs, no debris, no direct inlet for rain or snow.

Overall, all these setups provide cool air, so the cowl, plenum, hood scoop, or bumper scoops are all effective. After that, it came down to marketing, visual appeal, and hype.

The most effective setups are those that have an direct path to the carb or air cleaner, with no turns, no airflow killing hoses, etc.

If the 1966-1969 Olds OAI setups could have had a more direct path to the air cleaner, they may have been the most effective of them all. The 67 setup may have been the best, but the parking light scoops had a very small cross section.