Fiberglass hood mods... crazy?

DANO said: "The engine bay is a low pressure zone,

I am at a loss to understand what forces are at work to create "low pressure zone" underhood, when the radiator is a big, gaping hole in the front of the engine compartment and the inertia of the air in front of a vehicle travelling at high speed literally shoves that air through the radiator and into the engine compartment. Why doesn't that create a high pressure area in the engine compartment? Where does all that air go? The only escape route for it, on a flat-hood car, is to exit underneath the car, which is another high pressure area. That's why cars "lift" at speed, unless they're fitted with some sort of ground-effects (chin spoiler?) I can't see that under-car areodynamic environment "sucking" air from the engine compartment faster than the radiator opening and 100+ MPH of pressure is filling it up.

What am I missing here?


When hoods open unintentionally, the small gap created by the lifting of the hood to the secondary catch latch then creates a high pressure zone under the hood and reduces the high pressure at the windshield. The faster your going at this untimely event will generate more pressure.

Thanks for that great explanation; it is dead-on, and I feel pretty dumb not to have realized that, long ago... Makes all kind of sense...




I think if you just want to evacuate trapped air in the engine bay, a wide, low long hood scoop would do it, but this created a high pressure situation in the engine bay and in some cases if done incorrectly may reduce cooling through the radiator. I think if you had a wind tunnel (or a bunch of industrial fans and a smog machine) you could put a medium sized lip at the leading edge of your hood creating a low pressure zone across the hood to a point and place a vent prior to the high pressure zone at the windshield and let it vent air out. NACA vents inserted backwards in the hood may cause a venturi (sp?) effect on your engine bay and could help suck out air.

I could do that, and it would probably work as stated, but I don't want a scoop (or, scoops) on my hood, for strategic reasons... LOL


For your inlet, I've seen people actually put the filter in the cowl vent area, kind of a cheap air box, but I bet rain becomes a problem.

I'd bet you're right... and I don't really need water inside that system.
I may run a vertical, 4" pipe in front of the front wheel, with some sort of labyrinth to keep the water out... but this car will probably never again be driven in the rain, so, that might not be an issue. I have to do something, though; where that pickup is located sucks, big time...

Thanks for all your good ideas! I do appreciate them!!!