Gengis, as promised:
I couldn't find any reference to any emergency procedures in the PA18 manual. I seem to recall there being some kind of emergency procedures in the checklist - but the checklist lives in the plane, and the plane was out flying, so I couldn't check. I'm also not sure whether that was an official Piper check-list, anyway.
I did find a page of engine limitations, though. Hope they're useful:
Fuel: the minimum grade of fuel approved for use with this engine in 80/87 octane.
Oil Temperature: normal operating range: 120 to 245 degrees F (green arc)
Caution: 40 to 120 degrees F (yellow arc)
Maximum: 245 degrees F (red line)
Minimum: 40 degrees F (red line)
Oil Pressure: normal operating range: 65 to 85 lb/sq. in (green arc)
Caution: 85 to 100 lb/sq. in (yellow arc)
Maximum: 100 lb/sq. in (red line)
Minimum: 25 lb/sq. in (red line)
Engine Speed Limitations: The maximum permissible rotational speed for all conditions of flight is 2,700rpm (red line). The normal operating range is from 500rpm to 2,700rpm (green arc).
Use of Mixture Control: The mixture control is only to be used to maintain "Weakest mixture for maximum power" conditions when cruising at altitudes greater than 5,000 feet, or to avoid rough running due to over-richness in all other power conditions and must not be used to cause a drop in engine speed.
And that's about it!
FFF
-------------