dry tappet clearance

[N208ET]

I am in the process of checking the valve clearance on my narrow deck 360. I removed the hydraulic lifters and cleaned out all the oil before checking the clearance. All of them were found to be in tolerance, however, one was at .03, still in the tolerance range of .028-.08 but close to being out of limits. This was done with the engine cold. A friend of mine prefers the clearance to be on the other end of the scale, especially with the exhaust valves. What say you, leave it alone or try some shorter pushrods to gain a little clearance? I have ran the engine for 285 hours with the current clearance.

Randy
8A

[Walt]

I agree with your friend.

[rocketbob]

You're fine, just put it back together and move on. There are pros and cons of leaning towards either side of the clearance. There are several models of Lycomings that don't have hydraulic lifers and generally there isn't much of a problem due to expansion/contraction even in those engines.

[N208ET]

I got lucky and was given 3 shorter pushrods to use on the cylinders with minimal clearance. It seems to run exactly as it did before, but overall, I am happy about getting the clearance a little more middle of the road. Thanks again.

Randy
8A

[chaskuss]

Randy,
Glad to hear that you found some shorter push rods. I agree with Walt and your friend. The piston inside your lifter's hydraulic unit is designed [under oil pressure] to compensate for thermal related changes in engine component dimensions. It's always better to have that clearance in the middle or loose end of the range. An excessively [beyond .080"] loose lifter will make noise [ticking, just like on a car]. A tight lifter will cause the valve to not seat properly. This can cause a loss of compression and/or a burned valve.
Charlie
FYI, a noisy lifter can cause valve train damage, but it will take many hours [hundreds] for that to happen. A tight valve can burn in a much shorter amount of time.