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1966-2013
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13,741 Posts
Cooler air is denser than warm air, thus a denser induction charge which results in more power relevant to how much cooler the charge air is. (there's even math somewhere for it)

Sumping hot underhood air is pretty much always going to produce less power than fresh/cool intake air on the same engine.

This is why many folks notice more grunt when driving during a cool night vs a hot day.
 

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1966-2013
Joined
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13,741 Posts
Most all of the factory airboxes I've seen had the tube (or provision for it and the tube went missing) or some means of pulling outside air ('snorkel' airbox that pops out into the wheelwell for example) in some form or another regardless of carb, SPICA or EFI.
Though I vaguely recall one version that had a large 'hat' on there where the tube would normally go, but dunno what model it came from.

Shouldn't be any impendance created by the system other than what a given material or density of the filter(s) impart.
If the volume of the box itself is of adiquate proportion everything balances out nicely.

Side note: lotta folks create an issue on thier own by going too small for replacement boxes, or worse yet, those little filters that have the pretty chrome solid plate covers that sits about 1~1 1/2" off the intake throat opening. Might as well poke holes in a half tennis ball and stick that on there if going that route as it'll flow about as well and doesn't cost nearly as much.
 

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1966-2013
Joined
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13,741 Posts
A hose to the front end would perform a bit better than a downward pointing snorkel as it's pulling directly on outside air while the snorkel is picking up some convected hot air from the side of the block and sump. The hose can also provide a bit of ram air effect at speed depending on a few variables.

I wouldn't want to bet money on it, but I'd hazard that a down pointing snorkel might even have funny pressure losses or high turbulence dependant on the shape of the lower nose (air dam, chin scoop, bumper vs no bumper, etc.) and the effect it would have on underflow air in certain circumstances or speed ranges.

Either tube or snorkel is superior to sucking straight engine bay air as would be found with some aftermarket filter rigs.
 
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