OK, going back and reading a few earlier posts I'd skipped over previously:
Originally Posted by
Bend alot
FYI.
TCM IO520 engine - magnetoto engine timing 20 degrees BTC +/- 1 degree.
Bendix 1200 - E gap timing 15 degrees +/- 2 degrees
Bendix 1200 - points gap 0.016 +/- 0.003 thou.
Champion - RHB32E gap 0.016 - 0.021.
So one magneto can be 19 deg TDC, E gap 13 deg, point gap 0.013& spark plug gap 0.016.
The other mag 21 deg TDC, E gap 17 deg, point gap 0.019& plug gap 0.021.
Not sure what your point is here. You seem to be trying to suggest that all those tolerances can stack up to throw your timing off even more. Not true. The internal timing of the magneto (e-gap or point gap) only determines where the spark fires at the optimum time in the field rotation, it has nothing to do with where that happens relative to the crankshaft rotation. That is determined solely by the magento-to-engine timing. (ie: rotating the magneto on the accessory case so that point opening happens at a certain crankshaft angle) If your magneto is timed so that the points open at 22 deg. BTDC, it really doesn't matter whether your e-gap is set at 13 degrees or 17 degrees, the spark still fires at 22 Deg. BTDC. The e-gap setting only determines the efficiency of the spark generation. (that's what the "e" in e-gap stands for; efficiency)
Originally Posted by
Bend alot
** Interested as to your knowing the 25 degrees and not 22, did they allow you to be present? Normally owners/pilots are not allowed to oversee such work in many places
Jeeeez dude. Are you not reading anything? He told you how he knew. He Noted higher than normal CHT's on climbout, did an airborne mag check, noted a difference from one mag to the other, then when on the ground, checked the timing (as we later were told, using a Mag-rite electronic protractor set-up) and found one of his mags to have been set to 25 degrees BTDC.