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Engine Air Intake

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Atrus

Atrus

Jedi Warrior
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I might be jumping the gun again, asking this before reading Vizard’s book (it’s on it’s way!!!!), but does it seem odd to anyone that basically every setup I see keeps in the air intake for the engine right under the hood, near the exhaust as it is stock? Wouldn’t it stand to reason we’d want to pull in as cool of air as possible? I know when I was into modifying my Grand Prix everyone watched intake air temps like crazy, and some people went though painstaking efforts to duct in cool air.

For the Sprite, I will be doing an EFI conversion in the near future, and I was thinking of a way to implement a cold air intake for a sidedraft or downdraft setup. Downdraft, I am considering a custom hood scoop/filter setup…this is undecided, as I want it to look tasteful - thinking along the lines of the AC cobra scoop. I also realize there isn’t much clearance at all in there, so this is preliminary thinking. If I go sidedraft, I was considering incorporating a fender vent between the wheel and the windshield pillar. I was thinking I could duct in cool air from the driver’s side, and I’d relocate the heater intake to the passenger side vent.

Thoughts/Experiences? It just seems to make sense to me, cooler air = more power.
 
vizard has a lot to say about this, so all i can add for now is wait for the book.
 
Certainly, cooler air at the intake will give you a denser charge and more power. How much? Is it worth it? Most likely not worth making a cool air box. However, anything you can do to help vent hot air out of the engine compartment is worthwhile IMO.
 
Some run a duct similar to the heater intake duct to the carb side. Does it help? Dunno. When you are travelling at speed, there is a lotta air passing through the engine bay.
Some scoops actually cause a vacuum and defeat their purpose. Unless you get a cowl induction or snorkel, be careful what you use for a scoop if you want fresh air in the intake.

Also, don't try port injection on an A-series motors. The siamese ports will make it inefficient. Use a TB from a small car or motorcycle, something around the same displacement.

Cheers,
Derf
 
On my recently deceased Opel GT, they had, as OEM, a cold air intake. I bought a carb hood for my Weber so I could use it. Now I have a Midget with a Weber and the carb hood should fit. No good place to plump an intake snorkle through the radiator firewall on that side of the engine but just now I was staring at the engine and thinking I could put the carb hood on backward, route the intake "snorkle" between the rocker cover and heater box and tie into the heater air intake. Have to fit a filter into the mix. Just wondering if this is feasible or just a waste of time? Cold dense fresh air is better then hot engine bay air but enough better to care to fiddle so much? Of course, fiddling is part of the fun.
redlinehood.jpg
 
Use a separate source for air. When the engine is off the gas fumes from the carb will collect in the heater air hose and travel into the passenger compartment.
 
How tall is the unit overall? I shopped around for one for my bugeye but they are all just alittle to tall. where did you find it? Most of the ones I found were for VW"S and just would not fit.Measurement from the carb recess contact point to the top of the mounting nut would be great!
 
Atrus said:
Thoughts/Experiences? It just seems to make sense to me, cooler air = more power.
Click to expand...
Food for thought.
Air density increases about 1.8% for each 10 degree F. drop in temperature. If you have a 200 degree under hood temp. & 100 degree outside air temp, you can potentially drop the engine air intake temp. by 100 degrees. This amounts to an 18% increase of air density & engine power. Jetting richened to match.

The early Austin-Healey LeMans cars used a cold air intake ducted to the carbs from just behind the grill. They required richer carb jetting to compensate for the colder more dense air.

Drag racers & circle track cars have been using cold air intake to good advantage for many years.

It's essentially free horsepower.
D
 
Took some measurements. From the top of the carb body to the top of the hood is 3.25"
hoodstraight.JPG


"RamAir" foam filter thingy that was on there is about 2.5" high.
I have not tried bonnet clearance. (in the middle of engine pull at the moment).
Here's a shot with it pointing backwards to maybe plumb into heater duct. I'm not too keen on punching a hole through the metal on the driver's side.
hoodback.JPG


Opel GT had snorkle configuration sticking through radiator firewall as OEM and Opel guys like to retain it through all mods if possible.

It's a Redline Weber snorkle kit and it isn't cheap, $140 as I recall. Can rotate the hood 360 degrees.
Too tall?
 
Shoot its too tall for my BE needs to be < 2.75.
I think I'm going to have to crave one up out of foam and glass . Thanks for the measuements to bad it wont fit.
 
Opel guys had a shorter one, don't remember what but it led air into the choke tower, so they didn't like it much.
It was one of these. Have you checked all this stuff?
Jam Engineering
 
If you have side draft carbs It's pretty easy to do. Here is a pic of the A-H BN2 factory cold air intake.

The box is 4" by 2" & connects to a 4" diameter hose. The H6 carb float chamber vents are connected to the box for pressure balance. The front end of the hose is connected to a high flow K&N conical filter just behind the grill.
D
 

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It's all about the hole for me. I can't do, it, just can't do it. I'm WEAK!
 
I was messing around with the Redline weber adapter
https://redlineweber.com/html/application_guide/DGV_Snorkle.htm
It does fit under the hood if pointed backward.
If I route the intake hose back along the front of the heater box and plumb into the heater box intake, it could work. Of course, by then the air will probably be hot again anyway.
Is this worth the effort or should I just sell the thing, it's probably still worth $60, which I could certainly use for more "necessary" parts.
 
I think I would sell it, if you can not bring your self to cut a hole you don't need that. LOL

Heck unless you are doing lots of other mods to the engine 2 HP is not worth the effort, you will never miss it.
 
I think I'll hang onto it. Insulated tube around back of block and use the heater duct hole (since the carb hood has to point backward anyway, may as well route it that way). Few feet of hose and as cheap a K&N cone filter as I can scrounge and in theory I'd have cold air intake. You're teasing me that'd it be worth 2 ponies right? I'd for sure do it for that. Cheapest HP I know of. That and ditch the fan for an electric (which I have hanging on the wall BTW). Alright, enough, got to get the brakes in order before I go any FASTER!
 
Two HP is about 1% HP improvement.
 
ER: 2HP is about a 1% improvement in HP.
 
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