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Hi Dave,
In Germany I was able to find a generic air ducting at an industrial supply shop. It works, but doesn't particularly look the part. FWIW...
Neil
 

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1984 GTV6, 1973 Berlina, 1987 Milano
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I believe those are just drains.
 

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1984 GTV6, 1973 Berlina, 1987 Milano
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Oh, and I found some 3" flexible aluminum dryer vent at the local Ace hardware that worked nicely for the hose, more than enough for 2 cars for $8. The car seems a bit peppier with it installed.

Dude, my CAI totally gave me a 10 hp gain, I can totally feel it!
 

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Any good auto parts store will have Gates flexible ducting that will fit. Cheap, easy, looks good.
 

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Hi Ontario Alfa,
Sorry, it seems I didn't get any emails for the replies to the thread although I think I should have. I'll have to check my bb settings.
Yes, as others replied already, the nipples on the bottom are drains. The stock setup, as in the parts manual, shows them with hoses on them which go into a common part which I assume is a one-way valve to let water out but not let air in. I've never actually seen one of these valves though, my drains are just blocked off. (I think the last time the car was in rain was in 2003 or so...)
Cheers
Neil
 

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1966-2013
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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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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.
 

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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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1966-2013
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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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Sure is a lot of information here...
If the original poster is insistent on having the original piece of ducting, I'll sell mine and replace it with whatever.
 

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Parts book pages, FWIW. Also FWIW, my '71 1750 Spider has the type with the intake tube. I wonder if the covers are the same size and shape, so all you'd have to do is swap the front cover of the filter canister?

(Just saw after previewing the post that the two images look like they've been joined. I also see that the newer filter has the drains and OVS connection that aren't on the older one.)
 

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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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