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Old 07-18-2019, 09:45 PM
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Default Cold air intake plumbing/routing: Fit a BB?

I currently have a homemade air box that seals up to the L88 hood rear opening. The concept works (efficiency = ?), and with some string lengths hanging down over the hood rear opening I can see the strings being pushed inward at speeds above about 15 mph. I'd sure like to do some efficiency comparisons of that versus getting the air from in front/above the radiator, but damn, with the shape of the hood (particularly the dip/valley in the front portion of the scoop), and what looks like the fan being positioned higher in the car versus a small block position, I'm striking out trying to route a clean looking (and decent size) hose/tube to the carb airbox. Anybody ever run a CAI hose in a BB? I'd like to do some box interior pressure measurements, with just the present box, and then with the extra hose inlet (with perhaps a reed valve setup in the box rear to seal off the windshield area source in the event that the front hose setup supplies more air than the rear.

Longer story than I planned. Anybody have any thoughts on running a front air source in a big block?

Thanks,
Mike
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Old 07-19-2019, 04:11 AM
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Originally Posted by 69427 View Post
I currently have a homemade air box that seals up to the L88 hood rear opening. The concept works (efficiency = ?), and with some string lengths hanging down over the hood rear opening I can see the strings being pushed inward at speeds above about 15 mph. I'd sure like to do some efficiency comparisons of that versus getting the air from in front/above the radiator, but damn, with the shape of the hood (particularly the dip/valley in the front portion of the scoop), and what looks like the fan being positioned higher in the car versus a small block position, I'm striking out trying to route a clean looking (and decent size) hose/tube to the carb airbox. Anybody ever run a CAI hose in a BB? I'd like to do some box interior pressure measurements, with just the present box, and then with the extra hose inlet (with perhaps a reed valve setup in the box rear to seal off the windshield area source in the event that the front hose setup supplies more air than the rear.

Longer story than I planned. Anybody have any thoughts on running a front air source in a big block?

Thanks,
Mike
You must be reading my mind. I am almost finished moving the motor back some more until it put the throttle body (Wilson- like a big 4-barrel) just in front of the cowling lip. I will have to run a small cowl hood scoop with a rear facing opening, which I plan on having open in the rear and mated to an air box. However, I also have an opening above the radiator that is ducted to the front of the grill. Half of the air goes to duct work for the oil cooler, but the other side could be ducted around the radiator "chimney" (air from the radiator ducted vertically out the hood) and into the intake air box. I really like your idea of a reed valve set up that would let the highest air pressure source feed the engine. In the photo below you can see the opening (duct) above the radiator. The drivers side (half) is ducted through a scoop on the bottom of the hood to the opening on the driver's side that feeds air to the oil cooler. the passenger side half could be ducted into a 4 inch hose (or fabricated duct) to go down the passenger side of the engine compartment to the air box.

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Old 09-25-2019, 06:30 AM
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Are cool air boxes for injected motors?
I donít think they work well with carbs
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Old 09-25-2019, 11:21 AM
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Find a swap meet hood and graft on a 67 stinger hood scoop. Some guys were putting them on top of l88 hoods, but a careful graft might be better. Front facing should be higher pressure.
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Old 09-25-2019, 10:41 PM
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Constructive criticism...

I dont foresee a way to get clean airflow (for ram air effect better than the cowl) over the radiator and to the carb... Also, how much is that gonna weigh??
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Old 09-27-2019, 04:30 PM
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I was looking at this a while back. The immediate problem is the area between the top of the radiator and the underside of a big block hood. The other difficulty is when the hood is raised the underside is very close to the radiator so that doesn't give much room for a filter.

The first thing I found is that there probably is enough room above the radiator to run a duct. Can;t remember but I think it's about 20 square inches. The hood opening problem could be helped by restricting the opening of the hood but that makes it's own problems. Instead, you could move the pivot point of the hinges forward about 2 inches. That's what I did in the photo below. I tried this on my car and found it worked. Gives you a little more space for a duct.


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Old 09-28-2019, 02:34 PM
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Originally Posted by COLE SWEAT View Post
Are cool air boxes for injected motors?
I donít think they work well with carbs
Guys have been doing it for more decades than I can recall. There's no violation of the laws of physics in any of this.
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Old 09-28-2019, 02:42 PM
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Originally Posted by BBShark View Post
I was looking at this a while back. The immediate problem is the area between the top of the radiator and the underside of a big block hood. The other difficulty is when the hood is raised the underside is very close to the radiator so that doesn't give much room for a filter.

The first thing I found is that there probably is enough room above the radiator to run a duct. Can;t remember but I think it's about 20 square inches. The hood opening problem could be helped by restricting the opening of the hood but that makes it's own problems. Instead, you could move the pivot point of the hinges forward about 2 inches. That's what I did in the photo below. I tried this on my car and found it worked. Gives you a little more space for a duct.


That's a novel option/solution. I'll keep that in mind. I've already made a couple iterations of hinges in aluminum to cut weight and adjust the hood height, so I'm not too shy about fabricating one more iteration.
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Old 09-28-2019, 10:06 PM
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What if, similar to the L88 box, the duct was part of the hood? That way it wouldnít have to clear the hood when opening because itís already part of the hood. Then mate up to a stationary piece in front of the rad when in the closed position.
Iím curious what you feel are the downsides of the cowl induction?
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Old 09-29-2019, 10:17 AM
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Quote:
Originally Posted by vette427sbc View Post
What if, similar to the L88 box, the duct was part of the hood? That way it wouldnít have to clear the hood when opening because itís already part of the hood. Then mate up to a stationary piece in front of the rad when in the closed position.
Iím curious what you feel are the downsides of the cowl induction?
Didn't the early Crossfire C4's have ducts built into the underside of the hood that sealed on the air cleaner box on the engine?
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