Show me that AD For the 421C? I have never seen or heard that requirement for a GTISO 520.

Yes, but you don’t have to do all that stuff every oil change?

Every 150 hours you inspect the tail pipes

Repetitive Compliance Times Thereafter at intervals not to exceed 50 hours TIS or 30 calendar days, whichever occurs later. Thereafter at intervals not to exceed 12 calendar months. Thereafter at intervals not to exceed 500 hours TIS. Thereafter at intervals not to exceed 12 calendar months. Thereafter at intervals not to exceed 500 hours TIS. Thereafter at intervals not to exceed 2,500 hours TIS or 12 years, whichever occurs first. These inspection intervals are established to coincide with each regularly scheduled engine overhaul. Prior to further flight after damage is found.

FWIW, the AD estimates the part (b) inspection to take 3 hours. It's not just a visual once-over. It says to clean the components with a solvent, then dry. Remove heat shields, polish suspect surfaces with crocus cloth. Visually inspect the whole thing. Measure exhaust joint springs, then remove them, then measure them again, then reinstall them and measure them again.

you change your oil on your engines every 25 hrs?

is that normal for a 421? i thought it would be more like 100 hrs?

This is the reference I use, and it doesn't differentiate by model, just 300 and 400 series Cessnas. Do you have a better source?
https://www.dropbox.com/s/mzeia22v0hyaamo/AD%202000-01-16%20Exhaust.pdf?dl=0

This was something I didn't know about the 421's. So if you're on a 40 hour oil change schedule and 50 hour mandatory exhaust inspection, you're doing (2) shop visits every 50 hours?? Ugh.

This is the reference I use, and it doesn't differentiate by model, just 300 and 400 series Cessnas. Do you have a better source?
https://www.dropbox.com/s/mzeia22v0hyaamo/AD%202000-01-16%20Exhaust.pdf?dl=0

Section (b) is only a visual inspection... If you find suspect areas, you have to correct them prior to flying again.

"(b) At the Initial Compliance Time and Repetitive Compliance Times specified in Figure 1 of this AD, visually inspect the exhaust system for burned areas, cracks, or looseness. If any area of the exhaust system shows damage as defined in the Appendix of this AD, prior to further flight, repair or replace the damage part.
"

Items I mentioned are on the next page under Visual Inspection.

Yes but you don’t have to do those at every oil change.

Items I mentioned are on the next page under Visual Inspection.

Interesting enough, last week I was putting parts back on my 414 in preparation for the engine return after repair. My IA commented that the clamps that I have are the one piece clamps as (shown in the AD) and they do not crack. I looked at the wastegate clamp in my hand, handed it to him and said both sides of the clamp have 1"+ cracks in it... I guess no-cracking isn't really non-cracking..

So you’re passing along an alleged insult to a shop from a third party? That’s incredibly unhelpful.

Juan maintained my 421 and King Air. No, not cheap, but good.

Ronert

Robert,
I didn’t get it from a third party. The guy I know just posted on the Twin Cessna forum about his experience. I know him personally, and he is a good friend. So no, not a third party. His experience was indeed horrible. I have been following this ever since he bought his airplane, and sent it to this shop. The reason I used “alleged “ is because I still believe you are innocent until proven otherwise. The FAA will decide…

That's correct, we've got the 4-blade.

I'm told that the wheel covers and strakes are obtainable (and helpful), too.