proppastie
Well-Known Member
Having had a stuck valve and bent push-rod once a long time ago I was worried about my engine because of the rough running at full throttle if the engine was not fully warmed up. Looking at the weather I saw 2 warm days in a row so decided to take a look.....there are two Lycoming service bulletin/instruction as regards the sticky valve problem....1425A and 388C....One requires dropping the valve in the cylinder and ream of the guide and the other requires special tools to measure the wobble to see if you need to ream the guide of the carbon. There was a phrase in 388C about pressing the valve in to get it off the seat to measure the wobble, which when the special tool is on and the rocker arm is off and the springs are still attached I have no idea how it could be done.
Thinking about it I rotated the prop until the exhaust rocker was just pushing the valve in and off the seat....I then took a screw driver and pushed against the cap between the rocker arm and valve stem and "eyeballed" the movement......There is very little play maybe .001 between the cap and the stem so whatever the movement was it was close to the wobble of the valve stem. The spec. is between .015 and .035 and it looked as I had more than .015 and in any case there was wobble and I do not have to worry about a sticky valve. This method should work for any of the Lycoming engines when one suspects a sticky exhaust valve because of carbon or lead fouling.
Thinking about it I rotated the prop until the exhaust rocker was just pushing the valve in and off the seat....I then took a screw driver and pushed against the cap between the rocker arm and valve stem and "eyeballed" the movement......There is very little play maybe .001 between the cap and the stem so whatever the movement was it was close to the wobble of the valve stem. The spec. is between .015 and .035 and it looked as I had more than .015 and in any case there was wobble and I do not have to worry about a sticky valve. This method should work for any of the Lycoming engines when one suspects a sticky exhaust valve because of carbon or lead fouling.