So I brought our new to us M4-220C home last Sunday, and have put a couple of hours on it since then. Today I removed the cowling to get familiar with the bits underneath and get some part numbers for consumables, and noticed the right side (copilot's side) exhaust was quite loose. I could move it side to side a good half inch, and all the movement was coming from the stub exhaust pipes moving inside the cylinders.

Obviously this isn't ideal, and the longer it's run, the worse it will get. Does anyone know how common this is, and what's involved in the repair? It looks like there is potentially a lot of weight hanging off of the #2 cylinder exhaust. It looks like a bracket could be tied into the alternator bracket to take some of the load off of the #2 cylinder. Has anyone tried this, or something similar?

I'm sure some of these guys know what this looks like off hand, but could you post a picture of it? Might help to throw out some ideas

Are the studs all the way up and in?
Is there exhaust leaking past the gaskets, providing they are still there.
Don't know if you can use dammit memory - ah Helicoil inserts in the exhaust flange.
Answer is probably buried deep in the bowels of the AC 43-13.b close I hope

Have helped with a couple of Maule MT-235 or so. Exhaust were often shaking loose from not solid support on the lower end. Modified and fixed that condition. Tried to pry some of the tubes off to get the muffler? lower pipe ends repaired. EASIEST we learned the hard way was to unbolt the damned system at the flanges and drop the whole unit and let the repair shop deal with the rest of it.

PS - I have only worked on Maules with Lycs.

Trim

STUDS would be easy. These are short exhaust pipes that are apparently pressed into the cylinders. I can get a picture from my extra engine later today. I've talked to Susan Prall, and it sounds like she has some stubs that are slightly different diameters, but they're just production variances. I suspect that I'm going to need either some kind of shim or a high temp filler/epoxy of some sort...

The Franklin exhaust is very different from the Lycoming on the Maules.
The Franklin header pipe stubs go up into the cylinder casting and are held in by two half moon shaped keepers.
These keepers get warped, especially if the exhaust riser pipes are too tight at the joint with the headers.
The muffler hanging bracket often breaks because of its original mounting point (now changed) and if there is too much interference with the riser/header juncture, the keepers get warped along with the high heat there.
Often the keeper studs become stuck.

Trimtab, the reason the 6 cyl Lycoming/ Maule exhaust does not drop straight down off the header pipes is that the #1 and 2 headers are on an angle and thus not parallel.

GravityKnight wrote:I'm sure some of these guys know what this looks like off hand, but could you post a picture of it? Might help to throw out some ideas

It took me a few days, but here's a picture of the stubs/headers on my extra engine. It looks like one of the exhaust attachment tabs is cracked.


I dropped my plane off with my A&P on Tuesday, so we'll see how the repair goes. It could be pretty straight forward, but they were REALLY loose, so I'm crossing my fingers...

1:1 scale, If it is just a broken attach tab/bracket, it is easy to weld up. One problem is the rear support not doing its job, but the much more common fault is that overzealous mechanics over tighten the bolt which fastens the exhaust can riser to the header.
This bolt should not be cinched tight as the cylinders all expand/contract in different ways and movement at the slide joint is needed.
Use a locking exhaust nut and tighten to a point that you can turn the bolt with one finger on a 4" wrench.

Thanks Jeremy. I should clarify that the cracked tab is on my spare engine. I just noticed it when I was taking the picture. As far as I know, all the tabs on the flying engine with the loose stubs/headers are intact. Good info on the torque for the attachment hardware