David, When I bought my coupe N3047H, it had a bad vibration. After doing what you are doing, motor mounts, clearances, engine stuff, dynamic balancing, we removed the prop and took it to a prop shop. They promptly red tagged it!! (someone had drilled a couple of extra holes in the back of the hub)
A new prop and dynamic balance and empty wallet later and I could finally make out the writing on the gauge faces while flying. Bob D. 1946 415E N3047 "Honey" Susanville, CA --- In [email protected], "drdlhammond" <drdlhamm...@...> wrote: > > Hi John, > > How can I/we tell if the rubber motor mounts are bad??? The AP thought they > looked normal (i.e. compared to others he had replaced). His torque wrench > was "validated" about 1-2 months prior to my job (he questioned both the 60 > inch pounds - too tight - and his wrench but a second, older wrench was > almost identical). Should we further tighten the mounting bolts? > > Both magnetos checked good during the March annual and both have been acting > "normally" since (i.e. no difference has been noted during engine run up > prior to take off). Yes, the right exhaust pipe vibrates enough to touch the > cowling at its exit hole (has since I bought the plane a little over 2 years > ago). Otherwise, we have not found anything that touches the cowling. I > will pass along the suggestion to check for valve spring and lifter > malfunctions. > > The engine vibration reminds me of the old K&B 0.35 nitro/methane/castor oil > model airplane engines we used in the late '60s and early '70s. These > engines were mass produced and inexpensive. Regardless of how well the prop > was balanced, they vibrated! At the time, older modelers told me these > engines were not internally "balanced" and thus their vibration. How much > engine vibration is "normal" for a 43 year old 4 cylinder 4 stroke engine??? > > Thanks for your input! > > David > N95CV > > --- In [email protected], John Cooper <john@> wrote: > > > > On 8/14/2010 10:32 AM, drdlhammond wrote: > > > We could NOT tighten the mounting bolts to the prescribed 60 inch > > > pounds (we had metal to metal contact between the engine and the > > > mount). At 45 inch pounds there was very little clearance so we > > > settled on 40 inch pounds. > > > > OK, there's something wrong there. Bad rubbers, bad torque wrench??? > > > > Once that's corrected, there are many possible causes of vibration. > > How's your mag check? Any baffles, exhaust or intake parts touching the > > cowl? Broken valve springs? Bad lifters?.... > > > > -- > > John Cooper > > Skyport East > > www.skyportservices.net > > >
