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Thanks Darren. I know this design was stock on some models/years. Do you or does anyone know why it was discontinued? I don't have it on my '69 GTV nor (I think) did I have it on my '73 GTV, both with Spica. Can't remember whether or not I had it on my '67 step nose with carbs (long gone). The design makes sense but I wonder whether there is greater resistance to air flow at idle.
John
 

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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.
I'll snoop around more in my engine bay for an outlet. I've seen diagrams where there as a bracket bolted to the upper right corner of the radiator to aim the hose toward the grill but if I ever had one it is gone now. I don't have as much space for a tube compared to the pic in post #2, in part because my coolant overflow reservoir is right next to the oil/vapor separator. Also, the opening to my air canister is oval, not round, and points downward if that makes any difference. But thanks for the info.
 

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OK now I'm really curious

I've been looking at lots of engine bay and engine pic threads and it seems that the 1750 air intake plenums are like mine, with the opening facing down and opening up into the engine bay. Given that so little else differs between engines/bays, is this a worse design than the one where there is a duct heading toward the grill, or is it the case that the downdraft configuration preferentially draws cooler air?
 

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Thanks Bob, this helps a lot. Maybe at our next get together in CT someone will have the other front cover so I can compare them. Do you by any chance have a diagram showing how the snorkel is directed to the front grill in a 1750 with the other plenum design? Mighty tight in my engine bay unless I move the radiator fluid reservoir. PM me if you'd prefer.

I still can't understand why Alfa had this (my) design if it really compromises performance much, although I have to admit that my car is happiest when it is 50-60 degrees F.

Best,
John
 

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And my plenum has the front cover of the upper example in Bob's figure but also has the drainage nipples of the lower example. Talk about Alfa design
evolution in small increments!
 
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