The International Cessna^® 170 Association

Greetings,
Just pulled exhaust system off my '52 O300A equipped airplane today. Discovered some significant chafe wear on several of the intake risers produced by the exhaust tube riser clamps! Although some of the chafing is deep, I don't think intake tubes have been compromised...
Anyway, any recommendations for obtaining adequate clearance when I reassemble the exhaust/intake system? The exhaust clamps are the 4 bolt type, and I've heard mention of a 2 bolt type. The clamp material thickness seems to be the culprit in what I've observed.

Thanks,
Gary

I had that issue and the mechanic ground out a little "half-moon" in the edge of the clamps to give adequate clearance.

Gary, welcome to the club of nearly everyone else with slots worn in the intake from the exhaust clamps.

It takes the perfect position of each clamp and in many cases, fine tuning of the clamp itself to eliminate intake wear. If you could get your hands on a few of the 2 bolt type clamps, they can be the only way to go in some of the positions.

It is sometimes an impossible puzzle.

Good luck.

The two bolt clamps are not cheap but they do save a lot of headaches.
https://www.wagaero.com/engine-parts/ex ... pma-d.html

One side of the standard 4-bolt clamps has a flat spot at the bottom that goes toward the intake riser. They are a PITA to install, but I've never had a chafing problem with them. The 2-bolt ones look like they'd be a breeze to install...

So now getting ready to put it all back together. Purchased the 2 bolt exhaust riser clamps in hope that they may provide some needed clearance. If not, may just be doing a little grinding!
So whats an alternative to the metal rings that install under the shroud where exhaust stack exits and the 2 exhaust risers enter muffler. Mine are really worn/missing. There was actually a small piece of, looks like, high temp/asbestos rope filling a missing portion of one of the rings at exhaust exit stack...

Gary

Gary, do a search on the forum as there has been some discussion about these "seals" in the past. I am not sure what the key word will be to search them out, but hopefully you will have success. Mine are missing entirely and as I recall to find new ones is almost non existent. I did run across a source for some used ones, but elected not to spend as much as they wanted for them. George, Bruce or others will likely pick up on this and give you some better guidance. Except for making your cabin heater work better and maybe tightening up the shroud a bit I am not aware of any other benefits although I too would like to have a set.

Although they reduce the amount of "leakage" overboard of cabin heat and carb heat...they do not seem to make a lot of difference EXCEPT that, being metal, they vibrate and contribute to muffler-wear by thinning the muffler-wall.

There is a high-temp rope-like product often used in automotive and heating industries to act as a barrier to air leaks, and I've often thought of making some "doughnuts" out of that stuff to substitute for the seals, but clearly it's not on my "must do" list. (Certainly, don't make any such seals yourself out of asbestos .)

I measured the "gap" between the shroud and the muffler and cut a piece of some aluminium thick walled pipe that thickness . The pipe diameter was a little larger than the exhaust pipe. To get it to profile the roundness of the muffler ,this pipe piece was then placed in a large vice with 3 blocks of wood ,with one piece of wood in the middle and the other two on the edge . When assembled the edges of the pipe were then coated with a red color high temp silastic [ RTV 106 made by GE ] . This was to stop leakage and movement.
Note. Wear gloves when using this RTV.

Yes I actually located some high temp material at a local surplus store. Looks like flattened rope, figure 2" wide that I thought might work. But unable to figure out anyway to attach/bond ends together to form a closed loop. Can't melt it together, of course, fireproof! And you're right, old metal rings loose and will flop around inside shrouds. So all's going back together without rings or any seals. Besides, my old 140 didn't have anything similar, though shroud was a bit tighter around pipes....
But must tell you, it's been a true challenge getting clearance between exhaust risers and intake pipes on #'s 3-6 cylinders! Even with all new 2-bolt clamps, its required much adjusting, bending, and some minor grinding to establish adequate clearance... Can't figure out why Continental designed engine with such minimal clearances.

gahorn wrote:Although they reduce the amount of "leakage" overboard of cabin heat and carb heat...they do not seem to make a lot of difference EXCEPT that, being metal, they vibrate and contribute to muffler-wear by thinning the muffler-wall. ...

I never had that problem. My seals were soft aluminum and they did the wearing instead of the muffler. I couldn't have asked for the heater to work any better, but I never ran without them, so I can't speak to the difference without them.