Distance from Air Filter Above Carb to Carb Top??

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71GSSDemon

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If someone was going to mount a flat panel style filter element straight above a carb, how far above the carb should the minimum distance be? Or like a filtered air filter lid only without the rest of the circular filter element. Is there a standard distance to smooth out air flow? Carb/s would just be pulling straight down without bends or corners like a traditional round air cleaner. I am trying to lower overall height of my set up to fit in a hood mounted scoop better. Any thoughts would be greatly appreciated.
 
There is a minimum height above the fuel bowl vents that needs to be maintained, but opinions vary...
 
If you have motor trend TV or plus, checkout the engine masters aircleaner test. Simplified, down flow is better than across flow. Velocity stacks with a filter actually made horsepower verses no filter at all. And so did a salad bowl with a k&n filter lid.
Edit: the really short filters, like the flys eye filters were power killers. And they don't filter very well either.
 
This is why on some Holley and Holley style carburetors, the float vents are cut at an angle. You could essentially bring the lid right down against the vent and since they are angle cut, there's still plenty of room to vent.
 
If you have motor trend TV or plus, checkout the engine masters aircleaner test. Simplified, down flow is better than across flow. Velocity stacks with a filter actually made horsepower verses no filter at all. And so did a salad bowl with a k&n filter lid.
Yeah the salad bowl beat all. That was funny.
 
IMO, the minimum is 2-1/2 inches but I’d also call that to close for best operation. 3 inches or better is what I hope to get under the hood. And that is the problem, hood clearance. Here is an example of my issue on the wife’s car.

The car: A ‘67 Cuda w/a 360, RPM intake, AFB & a thick Edelbrock carb gasket which IMO is key for a cool running carb. I run the Mancini drop base filter bottom just so I can have some filter area since it’s cramped in there. The filter is a WIX 42044 to fit the black ribbed MP air cleaner.

From the top of the air horn to the bottom of the lid is a tiny 1 inch. This is choking the breathing I’m sure but I can not go higher since the wing nut pushes into the hood insulation. A hole in the hood is NOT an option nor is another hood.

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IMO, the minimum is 2-1/2 inches but I’d also call that to close for best operation. 3 inches or better is what I hope to get under the hood. And that is the problem, hood clearance. Here is an example of my issue on the wife’s car.

The car: A ‘67 Cuda w/a 360, RPM intake, AFB & a thick Edelbrock carb gasket which IMO is key for a cool running carb. I run the Mancini drop base filter bottom just so I can have some filter area since it’s cramped in there. The filter is a WIX 42044 to fit the black ribbed MP air cleaner.

From the top of the air horn to the bottom of the lid is a tiny 1 inch. This is choking the breathing I’m sure but I can not go higher since the wing nut pushes into the hood insulation. A hole in the hood is NOT an option nor is another hood.

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Thank you. I am most concerned though, with a filtered lid or a flat panel filter directly above the carburetor. No perpindicular flow at all. I am wondering how close to the top of the carb horn/vent/etc can it be - is there a distance.

I have seen the Engine Masters show with the filtered lid and the rest of the air cleaner assembly taped off made the most power along with the salad bowl.
 
Thank you. I am most concerned though, with a filtered lid or a flat panel filter directly above the carburetor. No perpindicular flow at all. I am wondering how close to the top of the carb horn/vent/etc can it be - is there a distance.

I have seen the Engine Masters show with the filtered lid and the rest of the air cleaner assembly taped off made the most power along with the salad bowl.


There is air blowing around under the hood. That doesn’t happen on a dyno.

One of the issues with the K&N style lids is depending on the air flow in the engine bay, you can have a low pressure area above the air cleaner. When that happens, and air that goes through the side of the air cleaner will flow back out of the top. You can see it on the underside of the hood because it will actually pull air up out of the boosters and that fuel and air ends up on the hood.

It doesn’t always happen. The only way to find out is to run it and see what happens. And it may only do it at certain speeds. Or it may not happen at all. It’s kind of random because the air flow patterns in the engine bay can be random.
 
Thank you. I am most concerned though, with a filtered lid or a flat panel filter directly above the carburetor. No perpindicular flow at all. I am wondering how close to the top of the carb horn/vent/etc can it be - is there a distance.

I have seen the Engine Masters show with the filtered lid and the rest of the air cleaner assembly taped off made the most power along with the salad bowl.
I see, well, I’d simply get as much as I could within reason. How close is bad? IDK
 
Rumble,
What makes you think 2 1/2" clearance is the minimum? Just wondering, do you have source/data that recommends this?
I do not see a problem in the pic in post #6, with a 1 1/2" gap. I spot a Carter/Edel AFB/AVS. The biggest size is 800 cfm with 1 3/4" t/bores, total area of 9.6 sq in. Using 8" as the smallest diameter of the A/C base where the 1 1/2" restriction occurs, I get 37.7 sq in of breathing area, 4 times the area of the bores so I don't see how a flow restriction could occur. Also, plenty of clearance above the carb vents.
 
No data handy to post. But what I have learn first hand.
More filter is better. More diameter is better. More pleats the better. Taller is better. (Seen from history) The ability to flow air straight down into the carb is better.

2-1/2 is a good a driver. This is a in general amount for driving down the road on the primary alone. More is better. Then again, it could be enough.
(Picked up elsewhere) Air doesn’t like to turn, it only turns so much so fast. More area above the carb makes turning the air easier as well as more available volume above it.

Mathematically working out the area of throttle bores to the available amount of element filtration doesn’t mean you have enough available air flow through the element or enough area to allow the carb to breath at it best. Air fuel ratios (via 02 meters on board) lean out with more filter. This is personal experience.

The 2-1/2 inch number is a general number that is reasonable for a simple driver to a in general hot rod build most often seen here. This number graduates higher as the power goes up.

On the above picture, when the fiberglass 6 pack hood was on the car, a taller filter was used. The switch had me lean out the carb and a noticeable throttle response change was noted. Small, but there and only under full throttle. Not driving around town or at medium speeds.

Also, a 4 inch high filter doesn’t have 4 inches of filter but just a little less. I also question just how many much of the filter itself is working & how well.

Since the question was general and not specific to the posters except engine specs or intended usage, a in general answer was given.

Rumble,
What makes you think 2 1/2" clearance is the minimum? Just wondering, do you have source/data that recommends this?
I do not see a problem in the pic in post #6, with a 1 1/2" gap. I spot a Carter/Edel AFB/AVS. The biggest size is 800 cfm with 1 3/4" t/bores, total area of 9.6 sq in. Using 8" as the smallest diameter of the A/C base where the 1 1/2" restriction occurs, I get 37.7 sq in of breathing area, 4 times the area of the bores so I don't see how a flow restriction could occur. Also, plenty of clearance above the carb vents.
 
Never considered blocking off the side filter and just running the top. Now I’m gonna have to try it!
 
Rumble,
My reply to your post #6 was referring to the area available for air flow between the high point of the A/C base & the lid. The area of maximum restriction. That is what I thought you were showing in the pics.
A/C filter size & flow through it is another story....
 
Rumble,
My reply to your post #6 was referring to the area available for air flow between the high point of the A/C base & the lid. The area of maximum restriction. That is what I thought you were showing in the pics.
A/C filter size & flow through it is another story....
Well, yea, ummm, the amount of flow available through or past the 1-1/2 inch area is making a 90* turn which IMO isn’t a lot of area and to much of a turn within that area for a hard acceleration or WOT. Easy driving, sure.

Hiw much can be passed through there is a good question but I think what I wrote above for what is generally good.

*I Think* we are on the same page? IDK.

IF I could get an honest 4 inches (or better) with a flow through top, I’d be good there. That only works with a hood in the hood and/or a scoop.
 
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