Muffler Issues

[GAHorn]

I wonder if we are all simply discussing a "fitment" problem.
If one curved and two straight risers are already installed and one attempts to fit the muffler to the installed risers...a fitment problem can exist because raising the muffler into position causes the muffer inlets to approach the riser ends at different angles. It may seem impossible to get all three to assemble correctly.
The solution is to attach the risers very loosely so that they can "wiggle" considerably even though their gaskets and nuts are in position. After clamping the muffler "snugly" (but not final torque) to the risers, then torque the risers completely to the cylinders. Lastly, torque the riser-to-muffler clamps, then the tailpipes and crossover brace.
If the system is within specification this technique will work very satisfactorily.
If the system is made up of a hodge-podge of re-used, re-welded, repairs from differing exhaust shops whose jigs are imprecise...then you'll have problems.
Exhaust systems stretch and thin out with hours of use to the point they conform to each other ....but not to another, previously worn out but "repaired" component that was not accurately jigged and overhauled.
It's one of the false economies of aviation...reusing old exhaust parts. Those pipes may look fine, but they are actually eroded until they are paper thin. Then when forced into position with other parts not of the same vintage or not properly jigged during rebuild, the old thin parts will crack and fail ...or the pre-loads they impart to the new parts will cause the new components to prematurely fail. ......False economy.
Exhaust systems are a major expense in an aircraft, and they are very commonly overlooked by aircraft purchasers (and just as commonly discounted in importance by sellers who wish to avoid the expense of properly rebuilding them.) A properly, completely re-built exhaust system on a 170 can easily be worth $1000!
And old worn out system with risers having thin, poorly fitting flanges can just as easily end up costing you six times that in cylinder damage and potential heat damage to engine components. (Or worse.)

[N3474C]

Actually, the curved riser for the LH side was longer than the one on the right, by about an inch. It even has a different part number, although I can't remember it right off hand. To make the mufflers fit, the curved risers on both sides needed to be identical. I ended up using my originals and replacing only the straight risers.

When I get back to Kenai on the weekend I'll look at the parts catalog again and show you what I mean. (busy with school at UAA now that vacation is over)


Chris

[GAHorn]

Chris, ....read my lips....
....the curved risers are all identical (or should be, as you noted) and they all are the same part number (PN 0550157-8). If you have one that is a "different part number" that doesn't fit because it's too long... then that is the problem. You need the same part number for all curved risers.

The IPC agrees with that.

(The reason the larger muffs you mentioned finding earlier didn't fit, is likely because they are 172 muffs, not 170 muffs. The larger 172 muffs will not fit beneath the 170 cowl. This is a common problem experienced when owners shop around without part numbers and fine mufflers "that fit C145 or O300 Continentals". Yeah, the engines will fit both 172's and 170's (at least the A engines do, but what about the 1964 172's that had D engines and larger cowls? 'eh?)

[zero.one.victor]

Speaking of mufflers a friend bought a NEW Hanlon-Wilson style muffler set for his O-200 powered C-150 from AWI (in Minnesota?). Don't know what they cost him,but they looked very nice. His purchase did not include the muffs,I don't know if they offer those or not.

Eric

[Bruce Fenstermacher]

I just happened to look at AWI's site and they do offer muffs. http://www.AWI-AMI.com

[AR Dave]

Pulled my Hanlon Wilson model 221-1 (stamped on shroud) this afternoon. Did a pressure test and found leaks AGAIN. One about an inch out from were the front riser enters. And a couple on the front end. This is off my 55 0300A and looks like the one in the pic. Has the heat sinks and all.
In the last annual we had a couple of holes that were welded next to the front riser. Am I done for?
My mechanic was telling me where to find a stainless steel welder this weekend, but I'm thinking how long before we pull it again?
How do you know when the metal is too thin?
George I saw your thoughts on it!
Also when I took those clamps off they were tight. Any trick for wrapping the Victor tape around the joints. And should I wrap the aluminum tape on top? Don't think there would be room for both anyway.
I'll get the books out and see when the muffler was installed.

$100,000 170B

[AR Dave]

Been reading through logs, STC's, & yellow tags, for 3 hrs all the way back to 1955. Can't see where the H&W's were installed, but see in 84 where they were welded on and flanges resurfaced. The engine was rebuilt in 75 and 85. After 85 the owner whom I bought it from, only flew 5-10 hrs a year. 600 SMOH now!! Total Time 3300 hrs. Is that about average?
I found 337's if somone needs them for Narco Mark X11 Panel Unit 5.7 lbs, Power unit 3.9 lbs , Cessna 175 wheel pants, 8" venturi, Bendix TR 641B Transponder, Kett Polaris's ADF, & much more.
George, in 78 a front cowl was installed with a vacuum system. Cessna P/nos. 0552002-72 (would that be for the year 72 cowling?)
Sorry for getting off the subject, it's really interesting to read the history of my $100,000 plane.

[zero.one.victor]

Dave,you might look thru your 337's & see if any of them might be useful to others,and send copies to the Association for their files. The 337's for the 175 wheel panties & the 8" venturi are likely candidates. Might want to include any accompanying documentation as well--parts specs,IPC drawings/parts lists,etc.
I just sent in copies of the 337 for the installation of my Cessna 185 jumpseat,and another similar 337 that I had a copy of from somewhere. Also copies of the appropriate pages from the 185 IPC for parts identificaion and documentation.Hopefully the next guy to do this mod will find them useful in preparing his own 337 and getting it approved.
337's for installing "new Narco Superhomer" or similar obsolete stuff probably won't be in great demand,so don't feel obligated to send in copies of all your 337's.

Eric

[N73087]

I have to start planning some R&R on my exhaust system. I have the: ”airborne solid copper blo-proof gaskets”, and they may be a problem because they are thin. The exhaust stack clamps are rubbing a nice gouge into the intake elbows. Thicker “spiral wound” gaskets would give a little more clearance between the clamps and the elbows (or would they?)
Are loose studs repairable with new studs and helicoils? Or is temperature a factor?
I have “four bolt” clamps on my stacks. I had “two bolt” clamps on my C140 W/ C150 exhaust system. What is the part number for the “two bolt” clamps? It seems they might be a bit easier to work with.
It seems I just read a posting that went through the exhaust gaskets and even gave part numbers for gaskets, clamps and SS bolts, but I can’t find it.

[AR Dave]

AircraftSpruce.com
Gaskets:
Spiral Wound Flange........ RA627429......$4.80 ea
Cont Brass Exhaust Nuts.. 22022 ...........$ .79 ea
Clamp Hardware:
Nut, Stop SS................... AN363C1032... $ .61 ea
SS Undrilled Bolt .............AN3C-4A ......... $ .23 ea
SS Flat Washer............. ..AN960C10....... $ .10 ea

[GAHorn]

I have to start planning some R&R on my exhaust system. I have the: ”airborne solid copper blo-proof gaskets”, and they may be a problem because they are thin. The exhaust stack clamps are rubbing a nice gouge into the intake elbows. Thicker “spiral wound” gaskets would give a little more clearance between the clamps and the elbows (or would they?)
Are loose studs repairable with new studs and helicoils? Or is temperature a factor?
I have “four bolt” clamps on my stacks. I had “two bolt” clamps on my C140 W/ C150 exhaust system. What is the part number for the “two bolt” clamps? It seems they might be a bit easier to work with.
It seems I just read a posting that went through the exhaust gaskets and even gave part numbers for gaskets, clamps and SS bolts, but I can’t find it.

The "four bolt" clamp are the correct pn's for the 170. The spiral wound gaskets are more durable than the copper thin gaskets and will likely give better intake elbow clearance. Also be certain the clamps are correctly assembled. They have a "flat" portion on the elbow side to give proper clearance.
Not picking on anybody but.....Why do people think they can maintain a complicated piece of machinery and not have an Illustrated Parts Catalog? Do they imagine that they'll always be lucky and find something to fit? Or would they prefer that the parts they order are correct parts because they can discuss them intelligently with others. It's difficult enough finding the correct parts for 50 year old airplanes, much less hold out any hope that incorrect ones will work. Get the IPC if you want to assure you always have the correct parts. (Don't make someone else look up your parts for you.)

[N1478D]

For an A model, the IPC for the 170A is not much help on exhaust part numbers with the HW system installed.

[GAHorn]

For a computer equipped person, the best way to get an IPC is probably McCurtain Technologies CD. http://www.mccurtaintg.com/ That way you'll have all 3 models IPC for one purchase price.

[zero.one.victor]

For an A model, the IPC for the 170A is not much help on exhaust part numbers with the HW system installed.

Thing to do is ask some helpful B-model type to photocopy the relevant pages form their IPC & then add them to yours.

Eric

[AR Dave]

AWI: overhauled, with a 15% discount for being in the 170 Club.
RH Muffler 0550157-32 $325
Curved riser 0550157-8 $78, straight riser 0550157-7 $45.
AWI didn't have the curved risers in stock so they had to have one made up for me. It came from a different location, Knisely is stamped on the side.