Cold Air Intake

[truckster]

Just thinking here... no current plans to cut into my firewall.

BUT... why not run cold air induction from the firewall? There's already cold air coming in through the cowl, so why not just plumb into that?

[Boog]

It works for race cars so why not a street car? Nascar racers have been ducting air from the cowl to the carbs since the 60s.

[Dead Parrot]

Keep in mind that most race car drivers wear a flame retardant full body suit in case of fire. They call it a firewall for a reason.

[truckster]

Originally Posted by Dead Parrot

Keep in mind that most race car drivers wear a flame retardant full body suit in case of fire. They call it a firewall for a reason.

But cutting into the cowl area wouldn't open up the passenger compartment.

[Boog]

I just remembered last year or so someone asked about a cowl plenum air intake option on a truck. It was a little known of option apparently. It was on a late 60s truck. I may be wrong.

[DieselSJ]

http://www.ramairbox.com/models.html

They have air cleaner housings for just that setup.

[D13]

So you want to open up a path for exhaust leaks and gas fumes directly into your heater / AC air source? Ummm... The guv'ment kind of made a bunch of rules about the factory doing that, for a reason.
If you look at the 70's cars with cowl induction they draw air from outside the vehicle, above the HVAC plenum, where there is a high pressure zone from air hitting the windshield at high speeds. The air in the plenum is actually under a vacuum due to the running of the HVAC system, particularly on any 70's up vehicle with the mandated continuous cabin ventilation.
NASCAR didn't have HVAC until recently, and their HVAC air does not come from a firewall plenum. If you are making a race truck and weld up all the firewall holes and remove your heater, then sure. But if you drive with heater or AC then please don't do this. CO poisoning and the smell of fuel in your cabin are not conducive to trucking enjoyment.

[AcampoDave]

It'd be a pain keeping rain and wash water out of the motor.

[LT7A]

I found this thread from reading another one and since it's current I thought I would post here as well. I give quite a bit of consideration on how to bring cooler air in for the motor (and let heated air out) and have read a bunch of threads on different forums.

Regarding the idea of contamination of the cabin air, I get the idea, but a good setup should keep a problem from happening IF, and it's an important if, there is an airbox that is sealed to the firewall. Were someone to just cut a hole in the firewall to let cool air in near the carb then there is a high likelihood of contaminating the air that the heater/AC draws from. If the hole is sealed to the airbox/carb, then I could see that some gas fumes could conceivably meander through the air filter, into the cowl trough, and into the cabin. But unless you're running the heater with the engine off, there's not a way to draw contaminated air in. As long as the heater/AC and the engine are both running, both are a source of vacuum and have an sizable amount of outside air to draw from based on the size of the plenum.

With regard to rain and washing, I think if the hole was above the floor of the cowl trough you'd be alright. Maybe screen it to catch big drops, but I would imagine that whether it's intake air or AC/heater air that it will lose the water droplets when it turns the corner to the intake area.

[mattfranklin]

If it's good enough for a Chevelle...
http://www.chevyclassicsclub.com/wp-...f/tech0913.pdf

[Ironangel]

If I'm not mistaken, the fresh air vents get their air through that plenum? I wonder if them Chevelle's had vents in the kick panels like our trucks? I'm not saying it won't work because if a "cowl induction" is properly isolated like or similar to what GM engineered for the Super Sports, it will work. Kinda labor intensive though considering that that cool air can be had at either side or below the core support. You have to be careful about piping a positive pressure intake that increases pressure and flow with speed? If your using a carb she'd be rich at idle and lean at cruise speeds? I like your thinking though because those bugs can and have been engineered out...But, there goes simplicity and one of the main reasons why I wont go LS or anything with an ECM in my old Chevy...Guess I'm old school, but I liked the first paragraph in that Cowl Induction add..."Picture this: Two gorgeous big-block Chevelles parked side by side,
both packing identical firepower. One’s got the standard SS hood,
the other’s equipped with a cowl induction setup.
What’s the big difference you ask?
Five, 10, maybe 15 more horses?
Nope. Actually the cowl induction
system adds zero horsepower to
your Chevelle. What’s the point then?" ..."Just sayin"

[LT7A]

Interesting assertion in that Chevelle article or advertisement. I wonder how you dyno test a cowl induction system at speed. Because that's when cowl induction comes into play. A stationary dynamometer would not mimic real world conditions. Not even with a fan.

[truckster]

It's a well-established fact that cold air induction will add 5 -10 horsepower by introducing denser air into the combustion chambers. Why the Chevelle would be any different is beyond me.