N/A carb hat or offset air cleaner opinions

Howdy!

I just figured out how to post pics again- worth a thousand words right?

I got my motor mounted in my project and the carb fitment is tight, but the air cleaner is tighter. It’s a 512 street build so I can give up a little maximum top end air flow but the motor will be thirsty even if I am running 2500-4500 rpm most of the time.

I can run a stainless domed screen to catch rocks but I want an aircleaner for street driving. I am thinking about welding up an offset round filter or maybe even one of those wedge style filters racers use in scoops, or maybe a carb hat or plenum with a big cone filter. I don’t want to choke out the motor or have wierd afr problems from turbulance in a hat or offset filter.

Anybody got info or ideas for me?

Thanks!

Oh and yeah I know my bowls are on backwards- just threw a 750 together for mock up 😆

How thick will the air cleaner element you use be?
The first cast aluminum bonnet I saw was back in the early 1960 for use on a 1961 Studebaker with a factory optional McCulloch superhcarger on it.
I may still have one of those for a small mouth AFB that I acquired on trade on something
My message is try both and run the one you like the most

I would begin with a "drop base" A/C bottom to take advantage of the radius shape around the opening. Extend it in all directions, especially rear (18 gauge aluminum + pop rivets, caulk it when done). What you want as result is large cross-sectional area right over the air horn. IIRC it's about 5.125" across for almost 21 In.2? You want double that (7.25" circle, 8.5" X 6.5" oval, etc. with as much height as will clear the firewall. Big internal volume (no such thing as too big) insures a large reserve of still air (intake velocity is traded for pressure), in which the venturis draw as if they were in free air.
Any form of screen: big restriction.

just curious . No screen ? What would cause these to be such a problem ? I have a similar issue though I run a dominator . Height clearance , no more than 3 1/3 ", no wider than 14". I run a screen with airplate sealed to hood
sorry for the interjection

Tex

So no go for plan B? Haha

Thanks for the responses. I wish somebody knew more about that $100 hat if it is a tuning nightmare I will steer clear. Going as big and tall as possible totally makes sense. The paper filter should slow down any air flow enough to prevent a lot of turbulence above the vents and butterflies- as long as it’s a big enough ‘filtered plenum’ it won’t get ugly and windy in there in a bad way?

My third idea came from the dollar store and is not the best one but for $6 worth a try for ABA testing...

WOOHOO !!
that's mine !

Tex

Questions are always appropriate.
The wire forming the screen is a miniature telephone pole (exterior surfaces are not actually smooth-n-shiny), and causes aero drag much worse than you would suspect. The openings must be microscopic to keep anything dangerous out, and they're the worst on flow. A screen opening large enough to reduce drag only stops birds.
The screen area has to be like 2-3 times the air horn area NOT to reduce air speed and CFM.
The usual curved dome is wayyy too small. If the rules actually required it (and forbade a filter) my guess would be to use the 14" common base and land a screen 1/2-dome 14" OD, 7" tall on it - that's 308 in.2 or 15 times the air horn area.
Other 1/2-domes ranked by surface area:
5.125" wide (stock AH): 41 In.2
8" wide: 101 In.2
10" wide: 157 In.2

Better hats are available.

maybe just a bigger diameter screen/ sieve


Tex

Seems a good candidate for a blow through style carb hat, metal tubing,and a conical filter mounted remotely.

Yeah Zippy I don’t really want a fuel injection looking carb hat with a big k&n cone filter but if it works it works. That’s why I included that pic of the spectre hat. I’ve read on some web searches that the low profile hats really kill horsepower and my problem is rear clearance not vertical. I wish I could find a nice 5 1/8” steel 90° Mandril bent elbow to shoot a straight column of air at the carb with no swirly corners to cause problems. I could fabricate something more squared off that has that general shape but then I would probably come out ahead just buying a hat like in the picture and a big cone filter.

The only thing is that would cost a couple hundred bucks and I’m always a bigger fan of making something than buying something.

I’m also worried about causing some kind of turbulence or bad restriction I want a simple reliable strong street motor not an exotic tuning nightmare.

Do you have an opinion on that hat in my pic? Got a better candidate?

Thanks!
Rdr

Polyspheric-

I have seen hats with velocity stacks inside to smooth the air but most of them are big doughnuts in shape and my tight spot is directly behind the carb.

What should I be looking at?

Oh ok. Well give it a whirl. I Don't know if that's a good design but I'm all for testing ideas. Maybe just rough it in to see what happens.

I've seen a ring welded to a flat tray holding a late model type flat filter. While that'd fit, I have no idea how it would flow.

You can find a drop base offset air cleaner base at Day Motor sports .
May solve your rear clearance issue.

Search "holley flame arrestor"

How about the plastic air horns that were on the Dakota's and 1500's late '90's early 2000's. I'll get a pic of mine later. It locates the filter forward of the throttle body.

www.ramairbox.com

Resistance to flow through screens increases with air velocity. IIRC its exponential. Screens can be used a airdams if properly supported.

As far as turbulance and flow. Don't forget how important it is to protect the bowl vents. Preferably the bowl pressure is staying the same (Holley) and certainly don't want erractic unpredictable fluctuations.
Skim through this thread for ideas - photos of various ways to do it.
https://www.tapatalk.com/groups/racingfuelsystems/bowl-vents-t15.html

Wow that looks like the old innovate message board cast of characters. I learned a lot there about emulsion, air bleeds, IFR mods, and holley tuning in general.

I went ahead and did the lazy thing and bought a setup. Dual 4” oiled cone filters into a tidy but not too small plenum. Hopefully it will smoothly feed plenty of air and fit ok.

I guess I will have a little modern bling under there after all. It’ll look awesome with the hood down! It is also a bonus that I get to keep my cabin vent scoop.

AIRAID does some pretty cool stuff.

https://www.airaid.com/carburetor_hats.aspx

Carb Hats, tubing, etc. I've never used it but have noticed it being used on a bunch of gear head shows.

Enough room for this? https://www.jegs.com/p/Moroso/Moroso-Offset-Base-Air-Cleaners/743351/10002/-1

The airraid hat is nice looking but I don’t think it’d fit. Those drop bases are smooth too but also go behind the carb too far.

This setup dropped right on and only needs a little hemmer and dolly work just behind it- there is only 1/16” now and I anticipate the motor will shake that much even with poly bushings. I’m going to try to neatly smash 3/16” or 1/4” clearance behind it. It looks like the hood will clear fine & if not the 4” tubes can get added to and routed with common turbo intake stuff. Or even a ram air or cold air setup later if I get bored of bodywork.