Air Cleaner height over carb?

[astroracer]

If any of you have been following my Bad Ast build you know I have a highly modified doghouse(engine cover). An issue with the current cover is the height over the carb. I am in re-design stages for the doghouse but would like some input on how much room is needed between the top of the air cleaner housing and the top of the carb. Right now there is about an inch between the cover and the carb so I will be increasing the height of the cover to gain room for the air cleaner. I want to keep this added height to a minimum due to shifter cable routing and dashboard issues.
If I raise the cover 2 inches will that be enough room to get air into the carb with no restriction? At this point I will be building my own housing to keep the height down and will use two cone filters out in front of the engine.
Thanks
Mark

[sam 74]

if its a decient sized carb with a motor that needs a high volume of air 2 inches isn't going to work, i ran a small air cleaner on my built 470 and it choked aft about 3000 rpm, there was no opening the secondaries or it would die out, i now have a 4 inch tall filter and a k&n filter top. i'd say a minimum clearence would be 3-3.5 inches, it all depends on your motors needs though.

[astroracer]

Thanks Sam, that's what I was afraid of. I have some work to do to get that much space above the carb. The engine is a 509 BBC. I will be running the stock 850 on it for break in and de-bugging. I guess I'll shoot for 3.5 inches which means 4.5 for cleaner to doghouse clearance.

[1966longroof]

Thanks Sam, that's what I was afraid of. I have some work to do to get that much space above the carb. The engine is a 509 BBC. I will be running the stock 850 on it for break in and de-bugging. I guess I'll shoot for 3.5 inches which means 4.5 for cleaner to doghouse clearance.

I you know any round track guys up in your area. Check and see if any are using drop-base air cleaners. Look at the inside and you can see how move the air. It might give you ideas on your design. Some guys are turning over 8,000 rpm and the using a paper 4" filter. However, the top of the air-cleaner is 2" above the carb. Just my .02

[mmosley]

Air cleaner I was running on my 446ci 550hp engine sits 2-1/8" above the carb flange. I have had it above 7000rpm with no issue. Air filter is 16" x 3.5" and has almost a 2" drop. It is barely taller than the vent tube and requires the carb to not have a choke tower.

http://www.knfilters.com/search/product.aspx?prod=61-4500

Optional you can also get the deflector:
http://www.knfilters.com/search/product.aspx?prod=85-56351

[sam 74]

I had a 14 inch element, you could do like Mosley and use a larger circumference like a 16 and that should allow you to go lower on the height. I do know it sucks to hit it and have the motor choke out. You also need to keep in mind that the straighter the air flow into the carb the better, from a performance stand point anyway.

[astroracer]

Thanks a lot guys. I put up a post on the Holley site just to get their input. Let's see if I get a response.

[Chevelle598bb]

My solid roller 468 had no problem turning 6800 rpm with a 14 x 4 k&n filter on a 2.5 drop base air cleaner. No difference in power between running it and not running it.

How close is the dog house to the air cleaner? I would be more concerned with that. The main thing is to make sure you have 1/2 inch clearance from the top of the vent tubes to the bottom of the lid of the air cleaner. You can trim them down if needed.

[astroracer]

I mentioned in my initial post engine cover to carb clearance is about an inch right now. I will try to maintain that with whatever I decide to do.
This is the set up I was planning to run. I may just stay with it and rebuild the top of the doghouse to fit over it.
https://static1.pt-content.com/images/pt/2013/12/ry3D400-26.jpg

https://static1.pt-content.com/images/pt/2013/12/ry3D400-27.jpg
The connector from the hat to the tube JUST fits over the thermostat housing.
This set up wreaks havoc with the front of the doghouse, which is what I am trying to avoid tearing up. I am using the front half of the original cover to seal the firewall as it was designed. The new cover actually seals to that and comes off without having to undo the firewall bolts. I'll take some measurements tomorrow to see how thing line up.

[Motown 454]

Can you angle it to one side and make it drop down a little sooner? Might save you form changing the dog house.

[astroracer]

Thanks Wayne, It's not that old and it is still an issue. I haven't touched the van to do anything since last November so I still need to get this addressed.
As you suggested is probably the direction this will go. I'll build a housing similar to the cast one. A little lower, a little bigger in diameter and angled down towards the passenger side of the engine so it can drop to rocker cover height and run forward.
Thanks for the input!
Mark

[Derek@ModernSpeed]

As a general rule of thumb, you want 3" of clearance between the top of the air cleaner, and the top of the vent tubes. Less than that, and you might see the engine choke.