Late '77 air filter housing?

[oldiron]

Can someone verify this. It has three holes in the front side of the filter housing. I doubt i'll be using this, since I'd have to fill the holes with something.

 

[Scoop]

Looks to me like a PO mod to increase air flow. Pretty sure the 3 holes are not stock.

 

[oldiron]

They look to be factory holes ( I could be wrong). There are none of the tell tale signs of p.o. hacking. All three are very clean and have locating tabs integrated in them. Again, I have been wrong before but I've not seen this arrangement before. Anyone seen this?
Greg

 

[904Bronco]

So here is a picture of my 77...

They are temp sensor vacuum switches, which were still available from Motorcraft a few years ago.

One controls the preheat stove door for warm air into the air cleaner

The other controls air to the air injection valve from the smog pump.

This is for the 49 state, non CA, smog equipment.

The 3rd hole may be for an electrical sensor, (two wires) that I saw on a 50 state smog equipped Bronco, but it was disconnected.

I have seen some Broncos with the 3rd hole plugged with a rubber grommet painted to match (hint, hint)

Doug

 

[spap]

My original CA 77 looks just like Doug's, its nice to see some thing that untouched and original..

 

[Scoop]

That's what I get for speculating! %) LOL

At least I learned something new today . . .

 

[jckkys]

The one on left when facing the engine is a cold weather modulator; a light blue plastic piece with 2 vacuum nipples that works in line with the air duct temperature sensor, on the bottom of the air cleaner. The middle one is a catalyst protection temperature sensor, an electric switch my none Cal. '77 didn't have. The third one is a TVS valve, but how it's plumbed isn't explained in my '77 shop manual.

 

[oldiron]

Well that certainly helps...I won't be throwing it in the parts heap. I'll just find an earlier one to use on the '74 I'm building. Thanks for the clarification. Anyone need this one?
Greg

 

[DirtDonk]

Just so you know you're not crazy Scoop, a LOT of owners did just what you were thinking. At least they did for the earlier years. I think more and more started just changing out their housings by the later models. Thinking they were improving things don't ya know.

My own had holes drilled all over it (albeit smaller ones) to aid air flow. Had to plug 'em up to pass smog back when it was being checked.
Not that the air was any hotter, since back then they pulled air from under the hood anyway. But it bypassed the heat riser which would slow down the opening of the choke in cold weather. Making it run richer longer and pollute more, all without really benefiting any that I could tell.

Paul