The International Cessna^® 170 Association

does anyone know how far the pipes should stick out of the cowling on 48 with c145 which way the tips should face

I don't know how far they should but I can describe mine (not sure I have a pic but can get one tomorrow).

They both stick out an inch or so, maybe a little more. One is cut so the angle faces into the airstream, and one is cut the opposite direction. I doubt this is correct, but it is how they are. A little longer would be better, as they leave exhaust stains (burns ?) that I have been unsuccessful at removing.

T.

If you look at pictures from the owner's manual the exhaust stacks protrude about 3" past the cowling and are cut parallel to the cowl.

Richard

From all that I've seen, that I suspect may be original, 3" inches passed the cowl is generious. Most look like 1 1/2".

If I was replacing them I would have the new pipes extended to about 3" passed the cowl however.

Unless I'm mistaken the Service Bulletins I handed out at Kelowna had a bulletin which addressed this matter. (I'm relying on a foggy brain cell at the moment, but I think that's where it is....I don't have that handout with me in DFW.)
There have been many discussions about how the tailpipes should face and how long they should be. Lots of opinions hold that they should face aft so that relative wind doesn't stuff exhaust back up the tailpipes (as if that could actually happen) resulting in several airplanes with even worse stains on the lower cowl due to the aft-facing pipes blasting the spent gasses almost directly onto the cowl.
Then there are those who buy the tailpipe extenders hoping to keep exhaust stains off the lower cowl and later, if they're lucky, find that their new inspector won't approve them and wants them removed and they didn't help reduce stains anyway. If they're unlucky they find an FAA condition tag on their plane out on the ramp or their exhaust system starts cracking from the added weight/vibration/moment of those extensions. (There is one extension that has obtained "approval" as tailpipe replacements, but it does not list this engine on this airplane, so whether it really meets the rule or not is debateable. They certainly don't meet the OEM's specifications for length. To me this means they must be altered during installation by the installer to the correct length...so what's the point?)
My faulty memory seems to recall the bulletin saying the pipes extend 1 3/4" past the lower cowl. Regardless of their length, the opening faces forward with the lower cut parallel with the curvature of the lower cowl (and as depicted in the IPC) which helps keep exhaust off the cowl.
(What exhaust that does get onto the cowl can be made easier to remove by using TCP in your fuel The stubborn stains can be removed with Dow-Corning "Scrubbing Bubbles" bathroom cleaner but....be warned....it's agressive stuff. Try not to do this too frequently. Spray it on. Drink a cup of coffee. Rub it lightly with a plastic pot-scrubber. Wash it off.)
Those little scrubbing bubbles are pretty amazing on other belly-scum and stuff too. I was shown this little trick by the Red Baron Pizza team back in 1980. They used it on their Stearmans and I used it on my Chief's belly. The fabric didn't seem to care, but metal planes and paint will not like it done too many times, I suspect.
Keep the lower cowl either waxed or oily.

My 170 still has it's original exhaust. The pipes protrude about an inch and the cut faces forward, nearly parallel with the cowling.
Mine is a 1950 A model. Perhaps Cessna changed things along the way so some years or models are different. Being an Engineer, I know about changes!

The bulletin was indeed issued back in the mid-1950's allowing for lengthening of the pipes to the 1-3/4" (?) .

The old tailpipes on my plane were cut off with the bevel to the rear and only about 1" outside of the cowl. That made a horrible mess of exhaust stains both inside and outside of the cowl.

When my exhaust system was rebuilt, I had the shop make the tailpipes 6" longer than they should be. Then when the plane was all back together with the cowl in place, the tailpipes were cut off about 3" past the cowl and parallel with the cowl. I wanted to make sure exhaust stains would be minimized by adding the additional length.

No new exhaust stains show on the cowl after 65 hours flight time. The old stains are still visible in the picture because I couldn't find anything that would take them off. They'll come off when the plane is painted.

hilltop170 wrote: When my exhaust system was rebuilt, I had the shop make the tailpipes 6" longer than they should be. Then when the plane was all back together with the cowl in place, the tailpipes were cut off about 3" past the cowl and parallel with the cowl. I wanted to make sure exhaust stains would be minimized by adding the additional length.

I bought the extended (+2") tailpipes from Wag-Aero. These are FAA/PMA for 170/170A/170B and the early 172s according to the paperwork that came with them. They stick out about as far as the ones on you aircraft. While they haven't completely eliminated the exhaust stains problem, it has greatly improved.

The Cessna Service Information Summary George passed out at the Kelowna Convention has the following on exhaust pipe length:

Quote:
Date: 8-10-51 S.N.L.
Subject: Hanlon Wilson Exhaust Pipes

The original supply of Hanlon Wilson Mufflers were received with the exhaust pipes longer than necessary so that they could be cut to proper lengths on the assembly line or in the field, in the case of Spares. In this case, it will be necessary to cut them to the proper length when they are installed in the field, as follows: The pipes should be extended on inch below the cowl surfaces, with the cut being parallel to the cowling.

Unquote

Depending upon your feelings about retaining originality, you could put John Benham's extened pipes on and clean up the cowling (ie: no holes in it) AND eliminate the exhaust stains from you cowling completely.

jlwild wrote: The Cessna Service Information Summary George passed out at the Kelowna Convention has the following on exhaust pipe length:

Quote:
Date: 8-10-51 S.N.L.
Subject: Hanlon Wilson Exhaust Pipes

The original supply of Hanlon Wilson Mufflers were received with the exhaust pipes longer than necessary so that they could be cut to proper lengths on the assembly line or in the field, in the case of Spares. In this case, it will be necessary to cut them to the proper length when they are installed in the field, as follows: The pipes should be extended on inch below the cowl surfaces, with the cut being parallel to the cowling.

Unquote

One inch, heh?

So... does that mean I'm three-quarters wrong, 3/4 forgetful, or 3/4 mindless? (I'm about 75% certain I've got a document somewhere that extends them to 1-3/4".)

gahorn wrote:Unless I'm mistaken the Service Bulletins I handed out at Kelowna had a bulletin which addressed this matter. (I'm relying on a foggy brain cell at the moment, but I think that's where it is....I don't have that handout with me in DFW.)

U MEAN U AXUALLY FOUN A BRANE CEL THAT AINT WORE COMPLEATLY OUT?

If you look at 50 photos of 170s, you will probably find 15 different forms, both length and angle of cut, of the tail-pipe extenders. If I could post a picture of mine, it would show about 5" of extension and the angle cut on the rear of the pipe. These extenders are exactly what was on '93D when we brought her home. I don't think there is any more exhaust stain on my cowl than any other configuration but there is sure less than some.

The most noticable exhaust stains I have encountered in the past was when 80 octane became un-atainable and I had to start to burning all 100LL (this was before mogas legality). Some staining on the cowl? Sure. But the most persistent stains were all the way (aft) down the bottom skins along the belly. The polished skin in that area turned a light blue-green color. It didn't take much to clean it off but it was very noticeable after a long flight.

Someone else can pro and con the Bartone pipes, the Benham pipes and the other exhaust mods that are available BUT I LIKE MY FANGS!

One of my hangar neighbors has a 210. To deal with the exhaut stain problem he riveted a sheet of stainless steel down stream from the exhaust - seems to work well.