Engine vibration

[acam37]

We now have almost 50 hours on our -4. While in cruise we've noticed a slight vibration that seems to be coming from the engine. It is best described as when you lean back to the point the engine starts running rough. The vibration is the same at different throttle settings and mixtures. I've never flown another -4 so I dont know if its normal. Engine parameters are all normal. The Lord mounts are not the same part number as Vans sells so that's one area that might be the culprit. The prop is a Catto three blade purchased used. Any suggestions on what else to check?

 

[AX-O]

Arlie,
this could be many different things from unbalanced engine/prop combo to something slapping around under the cowl to something a bit more serious. have you had your engine/prop balanced? Are your engine mounts on backwards (don't laugh, we found one on our field with 2 mounts backwards)? have you checked your exhaust hangers? what about the oil breather tube or sniffle valve hose? Is one of your baffles folded over and its vibrating in flight because of the airflow?

 

[acam37]

Axel, I will check the items you mentioned. I know the lord mounts are correct. Installed just like the diagram. Im kind of leaning towards the prop balance. The engine was just overhauled. The vibration is not bad but just enough to notice. Cant feel it in the stick but you can feel it if you put your hand on the dash.

 

[AX-O]

Sounds normal to me but... I am not flying it.

Can you record a video with sound and post it?