P&W 1830 Radial in 1/6 scale.

[bobm4360]

Because of the connecting rod geometry, the cylinder with the master rod is the only one where the piston TDC is the same as crank TDC. The others lead or lag by a small amount. In P&W 14-cyl engines the master rods are in #6 and #9 cylinders, but ignition timing is set from #1 cylinder. At one time, compensated magnetos to correct ignition timing were optional, but the later engines did not have them. Compensated mags were only used on the 14-cyl engines, the R-1535 and R-1830 series.

Regards,
Bob