[rotorwrench]

Peening should not be necessary if the fit is correct. It can still get loose when it's peened in but it will move around in the pocket and just get more fretted and loose. This is why the interference fit has to be so tight. Cast iron is easy compared to aluminum though.

When I was first getting into aircraft engine overhaul, we had a local shop that would rework the cylinders for us. This work was carried out with the aluminum head still on the cylinder. There were generally always cracks in the head that had to be welded up first. If a crack was in a place that couldn't be welded, they scrapped the cylinder. Welding would include repair of either or both spark plug bosses, valve seat pockets, and dome cracks. Machining was performed after all the welding was done to get fits for all affected repairs so that the inside of the combustion chamber looked like new. The cylinder bores were then plated and processed for piston fit. The valve guides and seats were then installed. They had to be tight due to the large size of the valves. The valves guides were were then reamed to size and the valves were seated and blued for proper seal on the valve faces. Rocker shaft bushings were replaced and fit to size to finish the process.

With all this work, we still could have problems with seats coming loose but it thankfully wasn't too often. All this process was eventually changed to improve the repaired product. This included unscrewing the head from the barrel so that repairs could be performed and the head could then be re-heat treated to relieve stresses. It made it easy to install the new seats too. New barrels were screwed on to make a much more reliable repair. The company started manufacturing their own cylinders since they had this capability under and FAA parts manufacturing approval (PMA). The reason they did this was that it was cheaper to make a new cylinder than it was to do all the repairs. We still had to have our oddball helicopter engine cylinders overhauled in this fashion since they didn't make new replacements for those.

Long story short is the company was bought out by Contenintal Engine Co for its PMA business and FAA approved processes then shut down and sold off. So now Continental is heavy into the Lycoming engine parts business and we have to buy the new oddball helicopter engine cylinders from Lycoming. So much for progress. It's just too expensive to carry the product liability for repaired parts now days.