The press fit tubes are a thin brass tube used extensively until Lycoming knew better. I would say they were the most common up till the late 50s or early 60s. Call it O-290s, O-235s and very early 320s.
I had not thought about what the lower thread size is as to whether I can cut threads in my engine case, or turn the threads off a tube.I would more than likely incorporate an upper support since it appear long press in tube might not have been utilized.
I am considering extending mine, these are nominally 1 ¼ OD tube and I can get a foot of 1 ¼ .032 wall from Mcmaster to work with. Probably be just about right.
Yes,
I do not know if the upper and lower threads are the same since I never paid attention to that in the past, logically I could use a standard Lycoming extension or if a medium length filler tube would work as such.
charlie i have a bunch of the different length screw in type, tell me the length your looking for and i will send you one. some are metal and some are a bakelite product.
That would be logical.
For my needs an oil tube of 10-11" would bring the fill up close to the cowl. I did not check what thread they use to determine if I can just thread my case, I will check that soon.
But logically it might be if I just threaded a 7ish inch fill tube into the 3" tube my engine has and use a long Dip stick would be the most reliable way rather than homebrewing something that could kill me.
Being that I will be welding up my own oil sump the calibration of the dipstick is meaningless till I know what mine calls for.