Air filter seal

[erich weaver]

I have an IO-360B1B (vertical induction) with AFP injection. Something is screwy with the fit between my FAB and the air filter, as when I look into the snout I can see there is not a good seal against the top of the filter. I think unfiltered and turbulent air may be screwing up my mixture in certain circumstances. Anyway, could somebody refresh my memory: How big should the oval cutout on the aluminum top of the FAB be relative to the air filter itself? That is, when looking at the top of the FAB with the filter installed, should I be able to see all, part, or none of the rubber rim on top of the filter?

Im assuming that top of the filter should be sealing against the top of the FAB, rather than sticking up slightly through the cutout and sealing against the AFP plate that the FAB gets bolted to, correct?

thanks for any assistance you can provide

erich

[Niko]

Erich, I am currently working on this part. I believe the top of the air filter should seal against the bottom of the mounting plate, the one that bolts directly to the throttle servo.

Niko

[Lars]

Originally Posted by erich weaver

I have an IO-360B1B (vertical induction) with AFP injection. Something is screwy with the fit between my FAB and the air filter, as when I look into the snout I can see there is not a good seal against the top of the filter. I think unfiltered and turbulent air may be screwing up my mixture in certain circumstances. Anyway, could somebody refresh my memory: How big should the oval cutout on the aluminum top of the FAB be relative to the air filter itself? That is, when looking at the top of the FAB with the filter installed, should I be able to see all, part, or none of the rubber rim on top of the filter?

Im assuming that top of the filter should be sealing against the top of the FAB, rather than sticking up slightly through the cutout and sealing against the AFP plate that the FAB gets bolted to, correct?

thanks for any assistance you can provide

erich

Erich, my recollection from two years ago is that the cutout in the top plate of the FAB is the same size as the outside edge of the rubber. Then there are aluminum tabs riveted to the top plate, pointing downward, that hold the filter's shape. The plate is supposed to be riveted to the fiberglass low enough that the filter sits slightly proud of the top plate. Then when it's bolted to the carb or (in my case) servo flange, the flange compresses the filter slightly. I remember 1/16" as the dimension, but my plans are several miles from here so I can't check.

I found one photo of the top plate that sorta shows what I described. I used J-B Weld as well as rivets to fasten the tabs. Belt and suspenders, if you will- I'm paranoid about self-deconstruction, though it's probably overkill. You can see that the cutout is obviously as large as the outside of the filter.

[erich weaver]

Originally Posted by Niko

I believe the top of the air filter should seal against the bottom of the mounting plate, the one that bolts directly to the throttle servo.

Originally Posted by Lars

Erich, my recollection from two years ago is that the cutout in the top plate of the FAB is the same size as the outside edge of the rubber. Then there are aluminum tabs riveted to the top plate, pointing downward, that hold the filter's shape. The plate is supposed to be riveted to the fiberglass low enough that the filter sits slightly proud of the top plate. Then when it's bolted to the carb or (in my case) servo flange, the flange compresses the filter slightly. I remember 1/16" as the dimension, but my plans are several miles from here so I can't check.

Huh. Different than I thought, but thats ok. On the plus side, may make it possible to fix my existing FAB by enlarging the cutout and building up the bottom with fiberglass to raise the air filter up. Alternatively, could perhaps place a piece of thin sheet rubber in the bottom of the FAB and glue it down securely to accomplish the same thing. Just thinking out loud..

thanks guys

erich

[Pat Hatch]

Originally Posted by erich weaver

I have an IO-360B1B (vertical induction) with AFP injection. Something is screwy with the fit between my FAB and the air filter, as when I look into the snout I can see there is not a good seal against the top of the filter. I think unfiltered and turbulent air may be screwing up my mixture in certain circumstances. Anyway, could somebody refresh my memory: How big should the oval cutout on the aluminum top of the FAB be relative to the air filter itself? That is, when looking at the top of the FAB with the filter installed, should I be able to see all, part, or none of the rubber rim on top of the filter?

Im assuming that top of the filter should be sealing against the top of the FAB, rather than sticking up slightly through the cutout and sealing against the AFP plate that the FAB gets bolted to, correct?

thanks for any assistance you can provide

erich

Eric,

As others have said, the filter should be sealing up against the FAB mounting plate, the plate that bolts to the bottom of the carb/fuel servo. You probably need to trim the top of the FAB box to allow the filter to poke through slightly and seat against the mounting plate. My top actually holds the filter in its oval shape at the top. That way, when you tighten the AN3 bolts around the perimeter of the FAB, the filter if firmly seated against the mounting plate.

[Jerry Fischer]

I found the filter wearing into the FAB so I layed a layer of BD cloth and West System epoxy laced with microballoons to self level the inside of the FAB. Problem solved, good seal and stronger Air Box.