Lycoming Spark Plug question

[ShadowGrass Shooter]

Guys, I am trying to put new plugs in my Lycoming 435 engine. It has always used automotive plugs since I bought it. I bought some new Champion Copper Core plugs but can't figure out the gap spacing for this engine. Every plug is completly different out of the box. There must be a spec for this engine.

Any thoughts out there??
Any help would be appreciated.

 

[Larry]

I generally run .015 on the bottom plugs and .018 on the top. When I tried to run the gaps larger then .025, the motor doesn't idle well and has to be leaned way out because the mags don't work well at idle speeds. I have used these gaps in everything from 290's to 540's and it works well, have no fouling problems like I have seen with the larger gaps.

Larry

 

[ShadowGrass Shooter]

Larry, Thanks for the input on the gapping. One more follow-up question. What is the proper way to shut down this engine? Is it to switch off both Mags? Is it to switch off the fuel pump and let'er run out of fuel, or is it to put the mixture control to full lean and kill the engine that way.

Any input would be great. Thanks

 

[cfth]

My .02 is to leaner her out and let it shut down that way.

 

[ShadowGrass Shooter]

I generally run .015 on the bottom plugs and .018 on the top. When I tried to run the gaps larger then .025, the motor doesn't idle well and has to be leaned way out because the mags don't work well at idle speeds. I have used these gaps in everything from 290's to 540's and it works well, have no fouling problems like I have seen with the larger gaps.

Larry

I changed to gap to what you recommended and it made a huge difference on Idle and start-up. Thanks again!!!!!!