OBS Motor mount Question

[Nak]

OK, I have my engine bay & undercarriage all cleaned up and I'm starting to put the new parts in. My motor mounts, the rubber encased in steel mounts that bolt to the frame, don't quite line up? That is, when the top two bolts are just barely tight, the bottom bolt hole surface is a good 1/4" away from the frame???? BTW, the original motor mounts are identical. It's like you need a washer between the frame and the mount at the bottom bolt. Is this the way it's supposed to be???? Like I said, the original mounts fit the exact same way. No washer was used originally. Both left and right sides are like this.

[Nak]

After looking at this closer, the bottom of the mounts are convex. So, tightening everything down is going to compress the rubber portion. Is this intentional? Something to hold the rubber portion tighter? BTW, these are GM mounts, not aftermarket. (Getting hard to find...)

[Cardot60]

That doesn't seem right, check to make sure you're using the right bolt holes. It might seem stupid but I've seen frames that have a lot of similar spacing holes in the engine mount area. Also you can check the bottom of the mount for any interference. Hopefully it's something simple for ya. I know I hate to re-invent the wheel with the little things.

[Nak]

It's the right bolt holes. The bottom of the mounts are convex, that is the cause. I'm just wondering if they are supposed to be that convex, so that tightening it down will compress the rubber. The old mounts also have a convex bottom, but not quite as convex.

[Cardot60]

Any relation to either one of these bushings? It's been a while since I've taken the frame mounts off but I do seem to remember the rubber bushings getting compressed as I tightened them down.
http://i.tfcdn.com/img2/N7bkHGwADYnL...v8*/fvUG-v8A.B

[Nak]

em-2637.jpgThe one on the left looks like what might be encased in steel. It doesn't look like you can get it out of the steel though? Here's a pic of what mine look like.

[Cardot60]

Well, looks like you've double checked the hell out of this one, maybe try tightening it down as even as possible and see how it goes?

[Nak]

Torques down just fine; flattens out as it compresses the rubber. I called a dealership & talked to an experienced mechanic. He said it's as designed, at least every one he's done has been that way. I just hate it when there's something I can't find written anywhere though. No where in any manual is it mentioned. Hell, the old ones were the same and they seem fine after 23 years. Must be OK... LOL. I'm just too anal sometimes I guess. I'm pretty slow at this shit because I just sit and look at stuff and try and figure out the engineering behind it before I continue...

[Cardot60]

On the plus side, being picky can keep you from making some expensive mistakes. You aren't working flat rate to my knowledge, so take your time.

[Blasphemy]

I just put new "clam shell" mounts like yours on my truck and had the same issue. I just got each bolt started on as many threads as I could (after some applied force) and zipped the bolts the rest of the way with my cordless impact. I think it's just a structural design and has something to do with the steel body of the mount. Mine turned out just fine and made a huge different from the mounts that were original from '98.