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BB_cuda
User Rank
Silver
Polyurethane resists oil
BB_cuda   2/29/2012 10:47:04 AM
While not as energy absorbing as rubber, polyurethane resists breakdown from oil. Aftermarket motor and transmounts are available in polyurethane. Cost is a little higher and installation is identical.  I just did a froint end rebuild on my old 89 honda accord. Most all of the replaced bushings got poly instead of rubber. Only the upper control arm bushings stayed OEM rubber.  My 67 Plymouth barracuda will be getting poly motor mounts, trans mount, and suspension bushings too. Sources are Energy suspension and Prothane.

Rob Spiegel
User Rank
Blogger
Re: Ah, Yes, the V-8 Corvair
Rob Spiegel   2/29/2012 10:38:23 AM
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Wow, that's an amazing story. I can understand the difficulty with the cooling, since it had to be built into the back. I would imagine you didn't take corners too sharply. I'm sure you're aware Corvair's are weak on sharp turns. It's the car Ralph Nader cut his teeth on. I enjoyed mine, though.

focusembedded
User Rank
Iron
My clutch behaving strangely was my clue...
focusembedded   2/29/2012 10:06:21 AM
NO RATINGS
I had a similar experience on my '68 Cougar a few years back.  I stepped on the clutch pedal as I went to start the car, and things just didn't seem to disengage.  In fact, the clutch felt like it was binding.  What'd happened is that a motor mount had gone bad enough that the position of the engine had slipped to where the bellcrank linkage for the clutch -- which is mounted at one end on an inner fender panel and at the other end to a boss bolt on the rear of the engine -- had come out of alignment.

Fortunately the car was parked at the top of a hill and I was able to get the clutch to release just far enough to get it rolling downhill in neutral.  I then *very* carefully felt for the opening in the dog teeth in the transmission and got it eased into second gear, at which point the engine started and I limped the five miles home in 2nd.

When I got home, two new motor mounts and a little clutch adjustment set everything to right again.  This time, however, I opted for a set of racing motor mounts that didn't have rubber.  The vibration is a little harsher, but the whole car is set up to be a little on the gritty side, anyway.

Jim S
User Rank
Gold
Engine mount failure
Jim S   2/29/2012 9:29:44 AM
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I had an old Oldsmobile Omega that had that problem. The bad mounts also damaged the transmission. They seemed to fail regularly on that car. It finally cought fire and burned, which eliminated that problem for good.

fatmanonabicycle
User Rank
Silver
Engine mount failure shakes Oldsmobile
fatmanonabicycle   2/29/2012 9:26:31 AM
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My 1981 Volvo 240 estate suffered an interesting related problem. The electrically switched Overdrive (I'll get there, OK ?) was tripping out occasionally. Unsure what was going on, I changed its oil (ATF), but to no avail, and frankly I don't like getting inside gearbox assemblies. Soon enough, I lost all drive almost instantly, and had the car towed to my usual garage, offering everything I knew. Two days later, all good, the O/D being fixed by- new engine mounts ! The old ones having gone a little soft after 125,000 miles, were deflecting, chafing the O/D wiring on the transmission tunnel, causing an intermittent short which caused the O/D to trip out. The loss of drive was due to a worn out clutch, which came on so suddenly because of Volvo's outstanding build quality, which had allowed the lining to wear down to literally ten thousandths of an inch thickness, worn away all the rivets and  fallen away during a gearchange; new clutch assembly, no damage to the flywheel, and away. So, an odd one on the engine mounts, but frankly a testament to the great engineering of real rear wheel drive Volvos. What these rebadged Fords are like, I don't know, but in terms of Engineering quality, that Volvo beat any of the many Fords I've had, though I confess I've always been happy with them.

Charles Murray
User Rank
Blogger
Scary problem
Charles Murray   2/28/2012 6:57:22 PM
NO RATINGS
"The engine had been sitting in the car without any attachments, except hoses and the throttle linkage." Yikes! Sounds like it was one hard expressway stop away from a catastrophe. The scary part is that engine mounts can fail so inconspicuously and dangerously at the same time.

oldtimer8080
User Rank
Gold
Early GM motormount rubber separation..
oldtimer8080   2/28/2012 6:35:00 PM
NO RATINGS
G'mas 1963 Chevy Impala had this problem long before GM acknowledged it was a problem.

The mechanics cure was a short piece of chain that we installed on her 327 SB engine mount AFTER we noticed a rise when we jumped on the throttle.

Doing a " brake stand " exposed the movement of the drive train. We had to replace the tranny mount when things got noisy back there...

The failure had nothing to do with chemicals. the bonded rubber simply tore loose under repeated flexing.

I saw plenty of this evidence when I worked in a salvage yard...

NOTE: Some of the mounts had VOIDS inside the rubber, which made the separation a matter of WHEN, not IF.....

 

David12345
User Rank
Platinum
Re: Yes, you can run without secure engine mounts, but,,,,
David12345   2/28/2012 5:48:42 PM
It seems that motor mounts can fail quickly in a highly stressed racing application; however, usually in a more modest street application it seems that the rubber holds-up well; unless, exposed to oil or other petroleum based liquids.  Lacking that degrading oil or ATF element, I have seen motor mounts last for the life of very high mileage cars.

The wide range in design seems to be whether the motor mount solely relies upon the bonded rubber to hold the engine assembly, or if there is an interlocking metal feature to back-up the connection.  The Chevrolet V8 "Safety Mounts" from about the mid 1970s on have that interlock.  The Chevrolet Corvair flat 6 mounts had that interlock.  The Ford Taurus sub-frame has that interlock (they just have a corrosion salt trap that makes the steel portions potentially unreliable; unless, the galvanized recall part is installed.) The 1964 Oldsmobile V8 mount had no steel interlock, just the bonded rubber.  From the readers comments it sounds like other vehicles such as the Econoline van also had no metal interlock back-up of the rubber attachment.

Clearly, it could be very bad when engines or sub-assemblies fall-out onto the road, or even when the engine can shift causing the throttle to pull-on harder and the transmission linkage to lock-up.  This is why there were NHTSB discussions with GM in the early 1970s.  This regulatory oversight probably facilitated the upgraded Chevrolet V8 motor mount design in the late 1970s.

Alexander Wolfe
User Rank
Blogger
Re: Yes, you can run without secure engine mounts, but,,,,
Alexander Wolfe   2/28/2012 4:12:33 PM
NO RATINGS
 It's my impression that engine mounts always fail sooner or later, because of the decay of the rubber that's involved. I had a reliable Camry where one of the mounts was bad, and it was too expensive to fix, so I just left it. But it definitely left an imbalance.

The other point is that real-world engine mount experience is never like those car shows on Spike TV, where they make a really nice bracket with a couple of bolt holes so it can't torque, and then they cushion it with a rain forest's worth of rubber. On real cars, most of the engine mounts don't seem to be all that well made.

David12345
User Rank
Platinum
Re: Ah, Yes, the V-8 Corvair
David12345   2/28/2012 1:52:20 PM
NO RATINGS
Had.  Yes, I had a V8 Corvair.  From 1974 to 1976, I built and painted the 1969 Chevrolet Corvair with the Kelmark Conversion Kit (Later renamed Mid-Engineering) to put the 327 Small block Chevrolet V8.  This increased the horsepower from the stock 110 hp 164 cid flat 6, to 325 hp, 327 cid V8. I rebuilt the suspension, rewired the dash, repainted it red, and installed a black interior. The V8 Corvair in it's heyday was a daily driver, autocrossed, run at Lime Rock, and entered into shows. 0-60 mph was around 5.2 seconds.  

The configuration had the engine in a cut-out where the back seat had been, on a steel box tube frame under a van type engine cover that I fiberglassed-up and carpeted.  The radiator was in the old rear engine compartment, but was marginal on cooling above 50-55 mph even with three electric fans in the fiberglass shroud.  The kit used the Corvair manual transaxle, turned-around and running backwards. (The V8 ran clockwise, while the Corvair flat 6 ran C'Clockwise.)  The 1966 to 1969 four speed saginaw transaxles were the strongest, but even with the custom input shaft, racing u joints, four spyder differential gearset, and special oiling provisions, the transmission would fail about every 3,000 to 5,000 miles.  I twisted 1 input shaft, 2 mainshafts, 4 clutch gears, 1 ring & pinion, and one set of u joints out of it from 1975 to 1984. 

The engine went into a 1969 Camaro project in 1984. I was in the process of matching a 1985 4 bolt main 350 cid SB V8 to a 1966 Olds Toronado 425 THM Transaxle to the set-up, with a front radiator, when a job and location change encouraged the car projects sale. I sold a 1958 Devin (Triumph frame and 1974 Capri V6)  to a stranger, the Corvair to a buddy in 1990 without the engine and transaxle. I believe the body was stripped and scrapped. I later sold the 350 engine and Transaxle in Memphis, TN. Alas, the break, and part-out demise of many project cars.

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