The International Cessna^® 170 Association

I just bit the bullet and paid for the exhaust system from AWI today. I've read and searched the forumns for all the exhaust options and the pancakes that I have, while still solid would need all new risers and tail pipe pieces. By the time I added them all up and had them welded, this seemed like the way to go.

So has anyone done this recently that can pass along any gotchas? Charlie at AWI mentioned he was trying to include some rubber gaskets that are placed between the muffler and the risers but hasn't included them yet, has anyone experienced leaks in that area?

Also, if anyone wants the pancake cores and shrouds, let me know, I'll send some pics and you can determine if they'll work for you.

Thanks!

Jud

rupertjl wrote:So has anyone done this recently that can pass along any gotchas? Charlie at AWI mentioned he was trying to include some rubber gaskets that are placed between the muffler and the risers but hasn't included them yet, has anyone experienced leaks in that area?
Jud

Jud,

Leaks in that area are not uncommon. I'd like to see what AWI has to go between the muffler and riser. Whatever it is, it would have to be very thin, like tape, so as not to preclude installation of the clamps, and would have withstand very high temps (I'd guess in the 1200 to 1500 degree range). Read this post http://cessna170.org/phpBB2/viewtopic.php?t=1044 for the muffler tape that George recommends. I couldn't find the tape George uses, so I bought some "muffler patch" at Auto Zone that is a gauze-like material that has to be soaked in the provided solution before installation. It is rated for the temps involved, but I decided not to use it, as it looks too bulky to go under the riser clamps.

As far as installation, I just went through this last week. By trial and error I found that the following steps should minimize the amount of "purple language" required to insall the mufflers:

First, install all 6 risers and new "spirotallic" gaskets with new nuts, but leave them loose enough to get significant "wiggle" in the risers, so as to let the muffler decide exactly where they need to be. (I don't know if it's kosher or not, but I also put some graphite anti-seize compound on the first couple of threads of the nuts.)

Next, on the number 2, 3, 4, and 5 risers make sure you use the clamp half with the "flat spot" to clear the adjacent intake elbow. Unless you have 4 hands, duct tape each of these in place on the riser before fitting the muffler, as they can't be located after the muffler is in place.

Make sure the shroud seals part # 0550157-29 (items 12, 28 and 40 on p89 of the B model IPC) are in place before installing the muffler to the risers. If you have the right side shroud with the 3-inch duct adapters, go ahead and install the bottom seal part number 0550157-30 (item 41 on page 89), shroud, and rear adapter part number 0550157-53 (item 46) loosely before installing the muffler to the risers. Tighten the shroud fully only after the clamps are tight. The shroud with the 2" duct adapters built in to the bottom seem to go on without much grief after the muffler is in place.

The riser-to-muffler inlet fit is fairly tight, so work the risers into the muffler inlets one at time, wiggling the risers and muffler as necessary. I found it easiest to work from right to left, leaving the curved riser for last.

The # 2, 3, 4, 5 riser clamps seem to fit best if rotated about 30 to 45 degrees clockwise from square with the muffler. This will give maximum clearance to the intake elbows, and reasonable access to the bolts and nuts for tightening. I found it easiest to insert the bolts through the "backside" of the clamps and put the nuts on the front. Once the clamps are tight, you can torque the risers to the exhaust port (200 - 210 in-lb per TCM service bulletin SB96-7C).

After the shrouds are installed, it's time for the tail pipes. My new left-side muffler from AWI didn’t come with the hole for the tail pipe clamp locator pin. If you're re-using your old tailpipes, fit them to the mufflers and check the fit through the cowling holes before match drilling the locator hole in the muffler. If you also have new tailpipes and they aren't drilled either, then you'll want to test fit the pipes as above, then install the cross brace, loosely install the clamp, and use the clamp locator pin to properly place the hole.

Hope this helps, and let us know how it goes.

Miles

Wow Miles,
If everyone folowes your intructions they shouldn't hve any problem with their exhaust. something I would mention (which I know isn't kosher) is also antiseze the muffler and riser conections. This practice is two fold, number one is you can remove the risers from the muffler with aerokroil and not a two pound hammer. second the antiseze works as a sealent to an extent so you won't have leaks until the soot fills the voids.
brad

Thanks Miles,

Charlie said he would have the exhaust to me in about a week, so I'll definitely use your guidance and let you know how I made out. Many thanks!

Jud

Brad,

I wish I had known about your antiseize idea for the riser/muffler connectons before I put mine together. I tried to come up with something to seal those joints but couldn't. My mufflers and risers are in great shape and fit good and tight, so I'm hopeful the leakage will be mimimal. I'll file your idea away for next time.

Miles

Miles,

Since you're the king of documentation lately, I was wondering if you had written down what hardware you used to fasten the clamps with your exhaust. I was a little disappointed when I recieved my new exhaust without any hardware for the clamps. I got the no-blows and the brass nuts, but that was it.

Looks like a another order for hardware. Anyone have a good place to buy AN hardware in bulk?

Also, which STC do I ask Velvet for to make this legal?

v/r,
Jud

Jud,

The bolts are AN3C-4A (3/16 dia, 1/2 inch long, 1/8 inch grip, stainless, undrilled, $0.24 ea from Spruce). The nuts are AN363C-1032, all metal stainless steel stop nuts, $0.69 ea from Spruce). You'll need 24 of each.

Spruce is a little on the spendy side, but I'm close enough to get next day service from UPS Ground. You might want to check prices at http://www.gen-aircraft-hardware.com . I just tried to check prices there, but their online store is closed until Sunday.

Miles

Thanks Miles,

I found that site through a google search as well. I'll check with them Monday. Thanks for the info!

Jud

Jud I use Freemans Just Plane Hardware for hardware. They are located in Georgia. Do a search for hardware here for other suppliers as well.

You don't need an STC to install the newer Hanlon Wilson exhaust on the early aircraft because it is approve by the TCDS. A log entry saying what was installed per the TCDS is all the is necessary.

To be a bit more precise, the log entry should reference the Cessna dwg. 0550157 per the TCDS. (See item 110)

rupertjl wrote:Miles,

Since you're the king of documentation lately, I was wondering if you had written down what hardware you used to fasten the clamps with your exhaust. I was a little disappointed when I recieved my new exhaust without any hardware for the clamps. I got the no-blows and the brass nuts, but that was it.

Looks like a another order for hardware. Anyone have a good place to buy AN hardware in bulk?

Also, which STC do I ask Velvet for to make this legal?

v/r,
Jud

I understand your disappointment. When the package arrives and you tear into it, one anticipates a complete "kit". But it's important to remember that a parts order is not a "kit", and also that while many install these exhausts using common AN hardware, the cadmium plated stuff will rust very quickly. It's much better to use the corrosion-resistant "C" hardware.

well the exhaust is installed after the 5-day owner assisted annual. I think the install was relatively easy, I had to trim some of the exhaust shroud tabs on top to get the clamps to fit on the risers correctly but other than that, I was pleased. I also installed all new 2" scat tubing for the carb heat system. I flew it yesterday for the first time in a long while and noticed when I pulled power abeam the numbers I had a few backfires (popping sounds from the exhaust, I'm just assuming backfires). I was wondering if the new exhaust has changed the engine back pressure or if the new scat tubing may have the mixture extremely lean now that I have all that air going where it should. I thought I might also have some carbon built up between the exhaust valves after sitting so long (since Feb.) or the old cracked exhaust may have effected it some as well. Or am I just being paranoid and the pops are normal?

v/r,
Jud

That is probably an afterfire, not a backfire. Afterfire is a result of a rich mixture, excess fuel burning in the exhaust.

Steve