new carb heat box

[spinningwrench]

Wondering about the zero clearance on the carb heat box. Vetterman exhaust says 3/4” is the absolute minimum clearance to their exhaust, 1/2” if in a very high velocity airflow such as an exhaust area.

[gregc]

In my case (Companion/angle valve O-360/carburetor) there was barely 1/16" clearance. While it probably would have been OK, I decided to use a different heat box. The thought of possibly having to re-work the lower cowl after paint etc. didn´t appeal to me at all. Also, K&N wouldn´t help with any info on the melt/burn point of the filter and I was worried about a melting chunk getting ingested. So in the end I took the conservative approach.

[spinningwrench]

I think that is a smart move

[Bcone1381]

Greg, I came to the same conclusion and made the same decision.

[noema]

While working on the baffles I finally made the big hole into the bottom cowl and put it on. First observation is the heat box sticks out less than anticipated, which is good. The cover sheet (which supposedly the same as for the Four Place) is way too big and it's not immediately clear how to make it fit.

The second observation is that about 1/3 of the intake filter is inside the cowl. What would be a good way of dealing with this? Option A) cover the top part and seal it against the cowl skin. Option B) build a steep ramp from the nose bowl to the top of the filter.

On a side note, I have pretty good clearance between the heat box and the exhaust (Patrol, Lycoming O-360, Vertterman cross-over). I could easily fit a heatshield in between if the filter gets too hot.

[Tyler]

IMG_3355.jpg Here is what I did. Now keep in mind I'm a first timer with all this, so I'm not the expert to look to. Anyway...mine came oversized as well, so I cut a bunch off of it and bent new flanges to fit my cowl. Originally it would extend from the edge of the nosebowl to the aft edge of the cowl, so I shortened it to be flush with the air box and to terminate at my cowl exit. But in doing that I ended up with a narrower aft edge. My ideal would have been to have this thing flare out to match the width of the tunnel at its aft edge. At this point I was ready to fly so I tested it as is. I figured if I needed better cooling, my first step would be to make a new one of these that had a larger aft edge dimension. But my cooling is great so I'm running it like this.

[Tyler]

IMG_3741.jpg
here’s another view of how that recessed piece looks