I have a 1972 Cutlass with a 455 transplant. While under the car today, I noticed the driver's side motor mount looks like it is cracked. I was wondering what ill side effects there may be to it being cracked. The few times I drove it since I've had it apart, there was not any noticable problems, besides the front end having a ton of body lean. I think when the guy transplanted the 455 into the car, he didn't upgrade the front suspension, so maybe he didn't install the beefier motor mounts. I'm just speculating though. Anyway what effects can I expect from the mount? Do I need to get it fixed anytime soon? And finally, does that mean I have to pull the engine to replace it, or can I just jack it up to unbolt it.

 

Replace it. Just jack the motor up a little to slide the new ones in. Sounds easier than it is though.

I busted a motor mount so bad once, the block slid forward and the drag link was rubbing my oil pan for the 50 mile drive home. I was sweatin' it...must have stopped at 7 times on the way home to keep checking it for a big hole lol.

 

Are you talking about the rubber motor mount or the metal frame mount? If the rubber motor mount, are you sure it's really separated? It's not unusual to see lines and cracks in the surface of the rubber. Power brake the car with the hood open while an assistant watches (safely to the side of the car!). If the mount is truly broken, the engine will visibly lift up.

 

Rubber motor mounts are the same for 350 SBO, and 455 BBO. In fact I had to order 350 motor mounts for my 455 in the 72 Cutlass. It was a hassle two stores and four, or five trips. And having the old ones did not help, the ones that looked exactly the same did not work, the steel on the bottom of the mounts sat on top of the bolts that hold the pads. Crazy, I had to use the 350 with the a notch at the bottom.

 

This is not correct. There are three different motor mount (and matching frame mount) designs for the 1964-1972 A-body cars.

TYPE 1. 1964-1969 SBO and 1965-1968 BBO. These are all exactly the same. The rubber mounts do not have the "fail safe" interlocking feature.

Type 2. 1969-1972 BBO. These are the "455 mounts" The incorporation of the interlocking feature required the cross bolt to be relocated, which requires specific BBO frame mounts

Type 3. 1970-1972 SBO. These have the interlocking design also, but with the cross bolt in the original position. The frame pads are reshaped from the early pads to clear this feature. Type 1 rubber mounts can be used with Type 3 frame pads, but not the other way around.

Most aftermarket parts houses, including specialty repro houses, have these mount incorrectly identified.

 

Ha wow! And that doesn't do any other damage? I will have to take some good photos of it tomorrow. It doesn't seem to be seperated, so it may just have a hairline fracture. Hell, it may just be how it looks. I have never had any expierence with mounts.

 

Well, you don't floor it until the engine flips over the passenger side fender...

A simple rev of the accelerator while holding the brake will give a good indication.

 

You can also listen for a clunk as your CV shafts engage when you put the car in drive. This is a common problem with transverse mounted V6s. Err... nevermind.