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Were both altimeters set to the same barometric setting, or just to airport altitude? If they are connected to separate static sources, one of those sources might have something wrong with it. Or someone blew into the static port and ruined that altimeter.

Someone forgot the nuts, or left them loose and vibration shook them off. The mechanic got distracted or just wasn't paying attention. The Dirty Dozen factors in aircraft maintenance errors: In this case, Distraction is a strong possibility. Cellphones should not be allowed on the shop floor...

Those gaskets are just composition material, and they get compressed when the nuts are snugged up. With the heat from the head, and just plain age, they take a set and lose their elasticity, and the friction that keeps them tight is lost. They get brittle and crack and can shed pieces that get...

What is? The tropopause? Never. It's found between 30,000 feet at the poles and 56,000 feet at the equator, with some seasonal variations from that, but never as low as 16,000 feet.

A 48-year-old airplane. I bet that exhaust has more than 475 hours on it. When the engine gets hot, it expands in all directions. The cylinders get farther apart, and so they force that exhaust system to stretch and bend some. Then it cools and the exhaust is compressed. Enough cycles like that...

The lapse rate has to do with the temperature decease with altitude, from the ground up. Normally, it's about 2°C per thousand feet. At this rate, or less, the air is stable and won't support thermal lift. But if that lapse rate gets a bit steeper, more than 2°C per thousand feet, air that rises...

The typical injection system as used on the Lycomings. The servo is mounted to the backside side of the throttle body, as you see it at the bottom right, with the "idle valve lever" on it. For the purposes of understanding the fuel regulation and flow, the servo is shown at the top left, with...

By the time I retired six years ago the Skybolt stuff had gone through at least three generations trying to fix shortcomings. They used too much aluminum, and galling and wear were a problem. The aluminum bits in the rubber shockmount would act up, and getting them adjusted and getting them to...

The above was posted BEFORE these two: You really should read the thread.

In Canada, mixing STC'd systems (on certified ships) is verboten, and the FAA might also take a dim view of it. Steve Wittman's death in his last Tailwind was due to fabric retention failure as mixed chemicals destroyed the bonds. From the Poly-Fiber installation manual...

That there. It stays flexible. We had a Citabria with Air Tech, and yes, it cracked up. American Champion used a lot of that stuff. Ray Stits used to say that it was the fillers in the urethane and PVC finishes that eventually caused the hardening and cracking. Poly-Fiber (which some of us old...

Lycoming wants a non-AD oil used for break-in for most engines because those oils don't have additives that reduce friction, and friction is what we want for proper ring seating. With those additives, the rings and cylinder walls are kept apart and don't cut each other until a good match is...

I would ask that shop if they would rebuild that engine again, for free, if it did not break in properly and had high oil consumption. Make them back up their recommendations.

From Lycoming themselves: https://www.lycoming.com/sites/default/files/attachments/Lycoming%20Reciprocating%20engine%20Break-In%20and%20Oil%20Consumption.pdf And from the referenced SI 1014...

I have been around homebuilding since 1972. I remember reading about broken crankshafts in auto conversions, many of them because of the overhung, unsupported PSRU pulley loads. They do break, and no amount of wishful thinking will change that. We need to learn from the mistakes and failures of...

Been there, done that for an E-AB owner. I designed and did the installation of a Subaru 2.L in a Glastar. By the time it was done he could have bought a factory O/H O-235 and been flying a year or more sooner, at no more cost. The Soob came with an RAF PSRU on it, but I had to build a complex...

There are no overhung piston loads on a crank. It is supported on each side of every rod. It's the overhung loading that bends the crank, a crank that was designed to carry the flywheel or torque converter, maybe 10 or 20 pounds. It's also designed to transmit straight torsion, not side loads. A...

It's not just the crank's bearing. The crank itself is being bent as it turns, and it fatigues, cracks and breaks. This is why most PSRUs have a support bearing on the outboard side of the crank pulley. The support structure for that bearing has to be extremely rigid, or it won't relieve the...

SOME single-engine airframes have that. NO SE Cessna has it. The stab is aligned with the fuselage centerline. The engines have no offset, either down or to the right. This stuff is common in Pipers and some others, and even the Citabrias have an offset fin. Cessna pilots actually have to learn...

And a crankshaft grinder, a cylinder boring machine, a cylinder honing machine, and crankcase line-boring machine, valve seat grinding equipment, piston and con rod and crankshaft forging equipment, along with the forge, centerless grinding equipment for the lifters... It's not something easily...