ORIGINAL: MOTORMAN37
I have quite a bit of experience running .12-.15 size Mod car engine's, and these mods do work if you know what you are doing.
All you have to do, is to look inside any of the purchased Mod Car engines that come with these mods to begin with to realize it really does work.
Another simple trick is to bevel the bottom of the liner, since most of the stock engines I have had apart do not have much of a Bevel.
I have never tried Modding plane engines with any of the extreme Mods, because I do not think they spin high enough rpm to make it pay off where the .12-.15 size Mod engines are easily spinning upward of 35,000 and more rpm.
This is exactly what I do to all my engines. I do all the work on the outside of the sleeve and have done OS nickel liners too there`s no risk at all of peeling due to this kind of work. I measured the improvements in all my aero engines and the Tower 75 immediately rewarded me with another 600 rpm, my MVVS 49 gave 500 rpm more, which seems to be about what the rest of my engines also increased by doing this. I have done buggy engines too, and lately I`m hooked on speed nitro boats . I have flow ported and polished my Dynamite .32 marine engine and fitted a bigger carb and a different pipe and now my Thunder Cat 31 flies (It actually gets airborne due to high speed alone)
I`m sure altering the timing will give even more power, but I`m very pleased with my results for this rather quick and easy and almost risk free mods