FAB - I don't get it...

I have a new Filtered air box to construct and add to an O-320. I'm having a problem seeing how this goes together despite looking at some other builder logs. In particular, the fiberglass housing is about 3.5? deep. The filter is 2.5" deep. The aluminum top plate is about 0.5" deep and recesses into the fiberglass housing. If I press the top plate onto the filter into the housing, the top edge of the top plate is about 0.5" below the top of the fiberglass housing which just does not look right and does not look like others that I see in builder logs. Other builders seem to have the top of the housing aligned more or less with the top of the top plate. What am I missing here?

Thanks in advance!

Cheers, Sean

Funguy said:

What am I missing here?

Thanks in advance!

Cheers, Sean

Click to expand...

The -320 airbox is different from the rest. On the -320, the filter is sandwiched between the plate which bolts to the carb and an oval disk which seals the bottom of the filter. The airbox doesn't touch the filter - there's probably a half inch or more of space between the bottom of the fiberglass bowl and the filter/seal plate.

On most (all?) of the other installations, the bottom of the filter seals against the bottom of the airbox.

Missing disk...

Hi Kyle - On my Bill of Materials dated October 31, 2007, I have no such oval disk nor do I see it in the exploded view... Maybe it became available in later versions? Do you have a part number for this? Thanks for the speedy response.

Cheers, Sean

I?m not sure what Kyle is referring to but on my o320 there is no gap. The top of the air box is trimmed down to match the top plate when it is in the proper position against the filter. Most Vans fiberglass parts need trimming to final size.

Chris

Funguy said:

Hi Kyle - On my Bill of Materials dated October 31, 2007, I have no such oval disk nor do I see it in the exploded view... Maybe it became available in later versions? Do you have a part number for this? Thanks for the speedy response.

Cheers, Sean

Click to expand...

My airbox is probably 20 years old, so there's every chance yours is a later version. I do not have a part number for that bottom plate, but since my airbox/filter/etc is apart right now, I'll take a couple of pictures as I reassemble it tomorrow and post them in this space.

A guess is that they have modified the installation and your new one is like what I have for the RV-10, where you snug the bottom of the airbox up against the filter to make a seal. In your case, that might allow you to trim the upper flange of the fiberglass airbox to match the flanged plate that forms the top of the airbox.

Kyle Boatright said:

A guess is that they have modified the installation and your new one is like what I have for the RV-10, where you snug the bottom of the airbox up against the filter to make a seal. In your case, that might allow you to trim the upper flange of the fiberglass airbox to match the flanged plate that forms the top of he airbox.

Click to expand...

Yep that sounds like the process I went through. Sounds like they changed something.

Chris

Thanks gents! Looks like I am just over thinking this. Sounds like I'm in the trim to fit boat.
Kyle - looking forward to seeing your photos.

Cheers, Sean

While you are building, and for anyone else lurking - on the left side of the FAB, put 426 rivets in to avoid the very common cracks in the snorkel on the left hand side where the FAB clouts the side during start and stop.

Gets worse with age - don't we all sag a bit, eh ?

The first picture is the year ~2000 version of the O-320 air filter installation (before I reinstalled the airbox). It has a plate that closes the filter on the bottom.

The second picture is looking in through the mouth of the airbox, showing ~3/8" of clearance between the bottom of the filter and the fiberglass airbox.

Thanks y'all

Thanks Mike and Kyle.

Cheers, Sean