Increasing the Air Flow to My Engine

[Pontiac787]

I’m trying to increase the air available to the engine in my '67 Mustang.  It’s a 427 with 3 Holley 2 barrel carburetors and a max RPM of around 6,000.  By my calculation I need about 100 sq. in. of filter surface area.

I am currently running a K&N E-1960 1 ¾” filter which, again by my calculation, provides about 50 sq. in. of surface area.  Unfortunately, I don’t have room for the K&N E-1963 3” filter because, height wise, the front of my air cleaner lid is very close to a hood support.  The car has a fiberglass hood with a functional 1966 style hood scoop.  I can see three options for increasing the air flow. 

1)   I bought an air cleaner lid from Cobranda with plans of modifying it with two K&N 66-0901 9" filter lids, one over each outboard carb. https://www.knfilters.com/search/product.aspx?prod=66-0901&pkid=5531932&rw=1

2)   Purchase this set of O’Brien Trucker 2 ½” Air Cleaners.  The front one should clear the brace and sit up into the hood scoop.  https://www.obrientruckers.com/ecom/product/239/2671/

3)   Notch the fiberglass brace on the underside of the hood so that I can fit the original air cleaner with the 3” K&N filter  https://www.knfilters.com/search/product.aspx?prod=E-1963

All of these options will theoretically get me to the 100 cu. in. of surface area.  I’m interested to hear your thoughts on which may be the better option.

[plovett]

I think option 3 is by far the best.  Then option 2, then option 1.

Option 3 will have the best flow path and allow the carbs to share the whole filter and area underneath.

I think option 1 is the worst because I believe the filter lids often don't work well, especially when over short side filters.  They reportedly cause turbulence over the carb entry.

Option 2 I'm not sure about.  Maybe okay.

JMO,

paulie

[WerbyFord]

agree w paulie.
From the website, Option 2 is $175, yow! We used to buy entire Mustangs for that, & I'm sure you could get another steel hood for that if worried about cutting your glass one. The only risk with the glass hood is they're already kinda flimsy so you'd have to judge it you could cut the braces.

The rule I like to use is, assuming a single quad and a 14" air cleaner, use 1" per 100hp. So since 14*pi ~ 14*3 ~ 40, that's about 40 sq in per 100hp. So for a healthy 400+ hp engine I like to run a 14x4 filter or about 160 sq in.

You don't really NEED that much, but anything less than that starts to cost you a few horses, then a few more. K&N wont hurt as much cuz they flow more.
The factory used about 1 inch per 140hp on a 14" filter, sometimes more, so that's more like 28 sq in per 100hp.

About the only way to tell is try it, but I guess you cant really try the taller one unless you cut the hood first.

[Pontiac787]

Thanks for the replies.  I need to get in there and figure out how much of the support I would need to take out. Those O’Brien filters are pricey but the K&N 3” is almost $100 on its own.

[TomP]

I don't think you need a 3" tall filter.  But there is little selection in oval filters now. If you could find a 2 1/4" that should be OK.

[Pontiac787]

Agreed. To find one is the trick! 

[plovett]

Go 3" tall if you can make it work.  Not only will you gain some power, but the filter will last longer before it needs cleaning.  And you will have a better flow path into the carbs.  Taller is always better, IMO.

paulie

[fryedaddy]

watch that youtube video that roadkill made where they tested i think top twenty air filter combos.you will be surprised by the results.it looks like air from the top makes more power than air from the sides.good video.

[plovett]

Yeah, air from straight above is probably ideal.  The air filter lids in conjunction with a regular side entry filter is probably not so good.  Especially since the air filter lids are usually used with short air filters specifically to get more filter area.  Height is the real positive, along with area, regardless if it is a side or top filter.   A taller conventional side entry filter accomplishes the same thing as the salad bowl filter.  It allows the air to turn and move more vertically into the carb. 

JMO,

paulie

[Pontiac787]

I took a few measurements and it looks like I’ll be able to fit the taller filter with some minor trimming of the fiberglass support. I don’t think it will affect the integrity of the hood much. Any tips for getting a decently clean cut?  I was thinking of using a close quarters hacksaw since the cut will only be about 12” long in a half-moon shape.

[Pontiac787]

watch that youtube video that roadkill made where they tested i think top twenty air filter combos.you will be surprised by the results.it looks like air from the top makes more power than air from the sides.good video.

Very interesting video.  Thanks for mentioning it.  It's helpful to see side by side comparisons like this.  I love that the old "flip the lid" option really does work. 

[Falcon67]

Yeah, air from straight above is probably ideal.  The air filter lids in conjunction with a regular side entry filter is probably not so good.  Especially since the air filter lids are usually used with short air filters specifically to get more filter area. 

And other tests and anecdotal discussions indicate that some filter top units (like K&N) actually cause metering issues.  On my tunnel ram I use two smaller filters that fit in the "hilborn style" scoop - no noted reduction in power or ET.