What makes the AC a "HiPo" AC? The size or the label?

 

Exactly 13.75”? Any chance a 13.875” will fit? It’s also 2.64” tall.

 

There's this one for which the application info says "65-68 Mustang 289 hipo"

 

That's the one to get. Premium quality, correct perforated screen, and correct inside and outside diameter.

 

Pretty sure mine’s a Mr. Gasket from O’Reillys

 

The summit 239142 air cleaner will fit the bill. It is 13-3/4" diameter. I recently bought one to replace my 3-in air cleaner because I put a 1-in open spacer on my single plane intake. The 1-in open spacer changed my tune drastically causing it to go much leaner and hesitate. It wouldn't even idle unless I enriched the circuit. I decided that instead of trying to tune the carb I abandoned the use of a 1-in spacer. I figured it just wasn't worth it even though Pipemax told me I needed a larger plenum.

Previously, I bought a Mr Gasket 1480A 2-in air filter and it was something like 13-3/8" diameter even though it's advertised as a 14-in element so I returned it. 😡

 

https://www.summitracing.com/parts/sdk-b7sz-9601-a?seid=srese1&ppckw=pmax-restoration&gclid=CjwKCAjwxNW2BhAkEiwA24Cm9Dh37-eHd7JBuTs9Lb3H7i9DjU7f7zMh9Rsd8g6p3zf-q2rqqzJAbRoCpCwQAvD_BwE

 

If you can get me the original FA- number, I have some original NOS Motorcraft filters, I may have one or 2

 

It's probably FA-41. kip

 

Adding more confusion to the fire, I looked in the MPAC and found the information below. I don't know if the part number given is a Motorcraft part number or a Rotunda part number. My owner's manual doesn't list the air filter element but does list a Rotunda oil filter part number. Maybe they're the same ... dunno

 

I know I have a few FA-50, C8AF-9601-A, not sure what they fit and I would have to measure to see what size they are

 

While the 2" is "correct", a taller air filter will give the air a little better path and reduce flow restriction by having more surface area. Think about how tall the choke horn is, 2" does not leave much room for air to get in. I can fit a 3" with Edelbrock RPM and have about 1/4" to spare.

 

I tried several air cleaners because of low hood clearance. The drop base air cleaners seemed to have very little clearance over the throttle opening. At least a 2 inch air cleaner has a bit over 2 inches of clearance over the throttle openings. It has more room over the openings than a stock air cleaner. It's good for about 500 HP.

 

@66coupe289 Would you have a link to the one you are using? I like the "orange" of the original but would like it a bit taller.