my cessna 170 with 180hp lyc has virtually just a puff of heat coming out, seems the carb heat hose is larger in diameter than the cabin heat hose and me thinks heat is just blowing out of carb heat box...anybody have a fix?? thanks, woody

Woody,

I bought a carb heat box for a mid 70's Cessna 172, but the Scout uses the same setup. I installed this system, so that it's completely separate from the muffler, then took ALL the heat off the muffler, and routed it into the cabin, in two cabin inlets. The cabin inlets and valves are available from Atlee Dodge.

We field approved all this, but it's all basically off standard aircraft, with similar engines.

The new carb heat is a "stack robber" type, so it doesn't use any heat from the muffler.

If you want to tweak what you have, first look VERY carefully at the muffler heat shroud, and see if you can find ANY gaps at all. I'll bet there are some. If so, cut and fit pieces of metal to close those gaps. Every gap is just passing hot air out of the system into the cowling.

Second, if your carb heat is making HUGE heat, and cabin heat isn't, try just switching the hoses, and see what happens. On my airplane, there was virtually NO heat in the cabin (and a large cabin) until we rearranged the muffler system. Now its toasty.

Finally, consider building a cloth curtain to close off the back seats, aft of the door posts. Use velcro to attach. This reduces the amount of area to be heated.

I can try to take some pictures of my system, but basically, it's just copied from a mid seventies Cessna 172.

MTV

Thank you so much I am going to try these tips, woody