The International Cessna^® 170 Association

My 48 has a carb heat diverter box, (not carb air box) with 4 outlets for scat tubing to attach to. Inside is a flopper on a hinge that has come loose. I will need to break the spot welds to split it to do the repair and installation of the flopper or get another from somebody who has the entire unit. I would rather buy one that is functional before I start drilling and beating this one apart. I can send a photo if you e-mail me. Duane Shockey duane4@sbcglobal.net My next step will be to put a want ad in the Flypaper.

Duane-
There are shops out there that do very nice work on old beat-out airboxes. Atlee Dodge in Anchorage will always get my business when I need airbox repairs.

Richard he's not talking about the air box but what some of use might call a Y but the Y has a third outlet so it's really not a Y.

The curved end of this Y or the bottom is what is connected to the heat box. The two outside legs of the Y except the scat from each muffler. The center leg of the Y then goes to the heater manifold on the fire wall.

The flapper or one way valve is in the leg that attaches to the carb heat box and stops a carb backfire from traveling up the heater scat.

These Y fittings were used on 170s and 170As and usually found when the auxiliary heat duct is used down the center flap handle console.

Here is a picture of the Y (lower left photo) from another thread we recently had and posted by Mark.


The exact same Y was also used on early 150s Duane so salvage yards may be a source. I bought one years ago at Sun N Fun for $5.

I wouldn't be afraid to drill out the spot welds then use screws to put it back together. You can also eliminate it all together by acquiring the 90 degree elbow that is used most often in our installations instead of the Y. Then the right scat goes directly to the heat box via this elbow and the left scat goes directly to the firewall heat valve.

I've run my heat/carb heat scat with and without the Y and see very little difference with either the carb heat or the cabin heat.

Thanks for the clarification Bruce. I saw that thread with that picture and was amazed at all the hoses and extra parts.

I also posted the picture below on that thread and made the comment carb heat and cabin heat are usually separated so there is always an uninterrupted supply of carb heat available no matter what is done with cabin heat. I know some 170s came with the combining air box from the factory but separating the two hot air streams really makes sense to me, and not just because that's the way it is on my 170, 180s and 185s are plumbed the same way separating carb and cabin heat within the muffler shroud.

It would seem reasonable to me all that extra lash-up (read extra maintenance parts and labor expense) could be removed and one muffler feed the carb heat and the other feed the heater. Much cleaner and also original factory design on later models. The backfire potential goes away also. I can't really tell from your picture but it appears the air intake boxes are the same on both type systems so it should be an easy job.

Thanks to all of you for your responses. I got two recommendations to expert repair places for carb air boxes. Maybe they also work on carb air diverters also. I really want to open this one myself if possible. I really wonder how wide the spot weld will be where the two surfaces meet. I plan to rivet the pieces back together if I end up doing the job. ThxDuane

Duane, keep in mind (whatever repair scheme you select) that any method of reassembly that involves loose parts such as screws, tinnerman nuts, etc. etc. should be external, so that no possibility of any loose hardware will result in the parts being ingested into the engine. (Spot welds are great. Rivets are less great. Screws/nuts are even less worthy.)

Good point George.

In this case both the screws and nuts would be outside the intake. BTW I used screws and nuts as a term loosely here to mean a means of holding the two halves of the Y pipe together other than spot welding.

What Duane is talking about is the "muff" that is used to pick up heat on the exhaust pipe on the early, Straight C-170, (Ragwing), exhaust system.

No BL. He is talking about the Y elbow in the center picture below which is installed as seen on the left photo with the red arrow pointing at it. On the right is the elbow that most of us have instead of the Y.



The flapper Duane is talking about is installed inside just above the elbow and below the three outlets. The whole unit is two pieces of aluminum spot welded together in the outer flange with the flapper hanging from a tube of aluminum spot welded to the inside.

Note One outlet of the Y at the top in this photo is folded in and it should not be.

Ah, so! I stand corrected.