C3 Broken engine mount in the UK
Thread Starter
8th Gear
Joined: Oct 1999
Posts: 8
Likes: 0
From: Dartford, Kent, United Kingdom
C3 Broken engine mount in the UK
Took my 75 C3 to a drag racing night last Friday here in the UK and now when I pull away hard the fan hits the cowling, so I'm assuming I have broken the left hand side engine mount, as that's the one that's being stretched.
Is this a reasonable assumption, and is it easlily fixable. Can I jack up the engine and slip a new mount in. I see in my Mid America catalogue that there are locking and non-locking mounts. What's the difference between these (what exactly is it that locks) and would either be usable without removinge the engine. Do urethane mounts transmit more engine vibration through to the car than rubber ones.
Surprised this has happened as the car had a body-off rebuild 4 years ago and I was only running mid 15 seconds at around 100mph.
Cheers, Rob.
Is this a reasonable assumption, and is it easlily fixable. Can I jack up the engine and slip a new mount in. I see in my Mid America catalogue that there are locking and non-locking mounts. What's the difference between these (what exactly is it that locks) and would either be usable without removinge the engine. Do urethane mounts transmit more engine vibration through to the car than rubber ones.
Surprised this has happened as the car had a body-off rebuild 4 years ago and I was only running mid 15 seconds at around 100mph.
Cheers, Rob.
Race Director
Joined: Nov 1999
Posts: 10,643
Likes: 8
From: Foxfield CO 1970 Convertible
The "locking" mounts are shaped such that the metal parts interlock. If the rubber or poly part breaks, the metal interlock keeps the engine from moving more than about an inch or so. You still have to replace the mount, but there usually isn't any damage to anything. With a "non-locking" mount, the engine can rock many inches and do considerable damage! Go with locking. I'm running polyurethane mounts and like them for street. Can't tell much difference from rubber. I'm not sure about solids for the street - even if you can't feel it, the engine is transmitting its vibrations to the frame through the mounts. Things eventually crack.
Safety Car
Joined: May 2001
Posts: 3,758
Likes: 3
From: Surrey
if the chassis wasn't designed to cope with vibration from a solidly mounted engine then I wouldn't take the risk (having seen what happens when vibration causes failure of a frame.... 
).I got a pair of locking mounts (next day delivery) from Corvette Kingdom. As you say, just jack up the motor slightly & slide the old out & the new in.
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Melting Slicks
Joined: Oct 2004
Posts: 2,662
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From: Knoxville Tennessee
If your engine vibrates, there is something wrong with it. It torques from left to right. the frames on C3s flex so much already, if you don't beef the frame it will crack. As for the solid mounts, there are too many people on the forum running them with major horsepower without problems. It does a great job stiffening the front frame area, fixing a motor mount problem and improved handling.
Bernie
Bernie
Race Director
Joined: Oct 2000
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From: Kansas City, MO ...I'd like to go fishing and catch a fishstick. That'd be convenient. - Mitch Hedberg
How do you go about raising the motor enough to make this change without the use of a cherry picker?
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
Chunk of plywood on top of a floor jack, under the oil pan. You don't need to raise the motor, you just need to hold it in place. The plywood has enough "give" that you won't damage the oil pan unless it's rotted anyway.
Le Mans Master
Joined: Jan 2003
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From: Tuttle OK
Cruise-In VIII Veteran
Race Director
Joined: Oct 2000
Posts: 11,891
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From: Kansas City, MO ...I'd like to go fishing and catch a fishstick. That'd be convenient. - Mitch Hedberg
Excellent. Now without lying, tell me it's that easy to change the trans. mount and body mounts as well.
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
The body mounts aren't supposed to be difficult if the nuts don't break free. I'm hoping it's not too bad, I have the poly kit, new bolts and new #4 reinforcements - both of my #4 reinforcements are on the verge of disintegration.
