ORIGINAL: ameyam
Opjose,
I totally agree with all that you have written. Went through all of that and added and reduced nitro content, changed mufflers (stock and pitts), tried larger fuel lines, swapped out for tried-&-tested tanks etc etc. The only thing I didnt try was replacing the engine and changing to synthetic (I used to run castor then). The 75ax was an engine I didnt fully run-in. Anyway, with the FS91SII, I corrected all of those things, some of them basics and dropped the tank height and I got it reliably working.
Ameyam
Ameyam
You were working with an out of tune, not run in, AX 75 and some unknown problems.
You cured things by switching to the FS91 ( which I'll bet had been previously used ).
I've fixed dozens of such problems for people who claimed the same issue w/o ever moving the tank.
Typically, pressurization, leaks, tuning, etc. is to blame.
On close to 30 of my own planes, I've never ever resorted to moving the tank no matter the differential.
Tank height did not cure your problems, something else you fixed along the way did.
I run both of those engines inverted on different planes w/o any problems what-so-ever, even though the tank height difference is greater than your U-Can-Do.
Tank height affects pre-start SIPHONING. That - IS - a problem if you do not preflight properly as I indicated above.