The International Cessna^® 170 Association

TIC170A family, I believe I have subject exhaust w/ subject clamp per Service Kit SK70A51-1 2-page installation document. I'm considering installing new hardware, perhaps new clamps, in an effort to reduce the exhaust leaks the A&P/IA doesn't like. The Service Kit doc ID's clamp PN NAS397-32; hardware is not ID'd. I can find no source for the clamps. McFarlane and others ID what appears to be the same clamp arrangement and w/ a PN A0750161-25 but it's for 1-3/4" riser dia.; mine measured at ~1.5". By eye I believe the bolts are 3/16", plus one flat washer and one metal stop nut. The hardware is in bad shape; I may 1st try replacing it but w/ what? The metal stop nuts are good for 450 DegF.
Thanks,
Steven

Steven,
Welcome to the forum!

-The NAS397-32 clamp is a ratchet type clamp for attaching the hose ducting to the muffler shrouds. They're generally replaced by Breeze clamps.

-The A0750161-25 clamp is an aftermarket p/n for a Lycoming exhaust system clamp on the C-172. It's equivalent to Cessna's p/n 0750161-25.

-Take a look at the Illustrated Parts Catalogs (IPC's) for the C-170B and C-172's through 1967. There you'll find the two bolt and four bolt styles of riser clamps. Wag-Aero used to make them but they've been bought out by Aircraft Spruce. Could be Wag-Aero is still manufacturing them for A/C Spruce. You're looking for p/n 0550176-50 and 0550176-51. I think 0550176-50 is now the two-bolt style consisting of two halves, p/n 0550176-46 and 0550176-47.

-I'd recommend the following 1200ºF hardware to attach the clamps: bolts MS20033-1, washers NAS1587-3, and locknuts MS20500-1032.

-Check out this thread for ideas wrapping the pipes prior to clamping them.

Most of the exhaust hardware and parts are available from OUR SUPPORTER … AWI…also known as Aerospace Welding …when you talk to them…ask for Charlie Felds…and Tell them you are a 170 Assoc’n Member and “George” sent you. (I don’t get anything but it reassures Charlie I’m still recommending them…which helps him justify the discounts and the Convention Donations he gives us.)

https://awi-ami.com/cessna-170a-b-exhau ... pped-image

The entire exhaust system for both the 170-B and our 172-C …from the cylinder-head to the tailpipes…..came from AWI. Excellent product!

Gentlemen, thanks for your replies. The AWI info sure looks like what I have. I had checked their web page before but missed this. I'll call them (your contact) Mon. I have other issues with which I'm grappling but will do so in topical threads.