Climbing through 2500 FT departing an uncontrolled airport a Bellanca pilot found his engine performing 'as if it were a lawn mower running on bad gas'. A successful return to the airport was completed.

Narrative

I planned on flying back home yesterday afternoon. Preflight good; started up fine; back taxied to the runway. Good run-up; everything as expected. Took off and made right turn to head north back home. Kept the climb at sixty MPH to 2500 FT since it was a bit bumpy down low and the landing options are limited over downtown. I'd just found a nice emergency field off the left side; reached for the throttle to power back and level off -- hadn't touched it yet when suddenly power went down from 2500 RPM to 2000 RPM and the engine sounded sick -- very sick -- as if it were a lawn mower running on bad gas. I glanced at oil pressure; looked for the field; then decided to do a 180 to see how far it was back to the airport. The engine was still putting out some power -- but barely. I had the handheld radio set to 122.800. Announced: 'Returning to Airport; Loss of power; clear the runway' (there was a C172 at the fuel pump that just started after I taxied out -- I never heard him make any calls so didn't know where he was).I looked ahead -- plenty of altitude with this amount of power. If it died between here and there I'd make the river. I didn't touch the throttle until I was two miles out. I was over 1200 FT AGL. I reduced the throttle slightly and it went nearly to idle. I slipped aggressively (very aggressively -- this airplane will fly sideways with enough aileron and counter-rudder) and was still pretty high. I kept the slip in until I was about five feet above the pavement; one third the way down the runway; then wheelied it on the upwind side (When I departed there was a direct crosswind varying from 6-10 KTS. I couldn't see the sock before I landed; but really didn't care).I rolled on one wheel for about 400 FT (I was doing about seventy when I touched down); and kept the weight on the upwind wheel. When the lift decayed I kept the tail up. Eventually both mains were down and I held some brake. I wheeled a long way; but actually only used about 1000 FT of runway. The combination brake and wheel landing allowed me to brake fairly heavily. I pulled the throttle completely to idle -- the engine continued to run; but unevenly. There was no possibility of go around and the end of Runway 23 has a nice tall road berm about fifty feet above the runway. I had plenty of runway left once I touched down. I taxied in; parked in front of the hangar; and ran it up -- lots of unburned fuel smell. The FBO owner and a mechanic came out -- we pulled the cowling off. Sure enough; number one plug on the left front cylinder was hanging out in space. They'll repair it there and I'll bring it back home later this week. Bottom line: Training took over. As soon as I heard the power change I had my field in sight; did a turn to lose altitude. When I knew I had residual power; made for the airport; kept it high; had an out if the airport wasn't made; and slipped aggressively and wheelied when it was the only option. Practice engine outs; practice slips; and make sure you know how your airplane will fly at different reduced power settings.