<VV> Motor mounting

[HallGrenn at aol.com]

In a message dated 2/13/2010 10:08:17 P.M. Eastern Standard Time,  
Sethracer at aol.com writes:

I agree,  Hank, that the motor mount is a place where a small  inspection 
goes  a long way. That said, Charles mount did not fail. A  catastrophic  
internal failure of the rubber in either the early design 65-  or the  
later design 
66-69 mount will not allow the motor to drop out of the   chassis. There 
are 
internal steel mechanisms to prevent that in both  designs. On  the late 
models, there are a pair of crimp-design lock  nuts holding the rear  
engine 
bracket to the mount. There are four  regular hex-head bolts holding  the 
other 
portion of the mount to the  rear frame rail. ONLY if all four bolts  fall 
out or both nuts fall  off, will the mount will depart it's designed  
position 
and the  engine (usually) drop down.


Having had an engine drop at the rear mount at 75 mph in my first  '68 I 
can say I agree with Seth and understand Charles's and Hank's points,  but I 
would want to know how Charles's car engine mounts failed.  In my  case the 
mount didn't really fail--the "Corvair specialist" at the local Chevy  dealer 
replaced my clutch by unbolting the engine from the transaxle and pulled  
the two parts down letting them hang so he could access the clutch.  A  few 
months later the engine dropped--one of the two rear mount studs had broken  
and the other stud was stripped and its bolt was gone.  The "bang" and  
dragging noise really got my attention.
 
I have complete confidence in the engine mounts themselves.  Even if  the 
rubber isolation portion fails you still have mechanical backup as Seth  
points out.  Abuse and stupidity (sometimes together) will overcome even  the 
best design.  The DC-10 got a bad rap after that American Airlines  flight 
lost its left engine and pylon on takeoff killing everyone on board--not  
because of a design flaw, but because AA mechanics took a shortcut and unbolted  
the three pylon shear bolts from the wing when they switched engines instead 
of  doing the extra work to remove all the engine to pylon fasteners--it 
saved time,  but unnecessarily stressed the three pylon shear pins.  The 
result was the  rear pin failed and the whole assembly tore loose causing the 
plane to  crash.  The engineers couldn't have anticipated that any more than 
they  could have anticipated the mechanic who cost me several days work and a 
few  hundred dollars in tow charges, the repair bill and other  expenses 
when my engine dropped.
 
Bob