RealDealZ28

I’m having trouble installing Prothane polyurethane motor mounts on my 2000 Camaro Z28. It’s an LS1/automatic car. Has anyone ever encountered a problem installing these—I mean, beyond the usual hassle of changing motor mounts? I bought the inserts that Prothane offers, the ones where you drill out your original GM mount, install the poly inserts, and reuse the original metal/clamshell portion.

The problem I’m having: these mounts are nowhere close to fitting. When I say they’re off, I mean with one side assembled with all of the bolts partially tightened, the other side is literally ½ to 9/16ths of an inch away from fitting in the frame mount. It’s so bad that the hole through the middle of the Prothane insert (the large 18mm bolt and nut) is over a half a hole off from lining up with the hole on the frame mount.

Both I and another mechanic at our shop have used all of our usual tricks: The car is on a lift, so we’re working from underneath. None of the motor mount bolts have been fully tightened, so we should have plenty of movement. We’ve used transmission jacks and pry bars to raise, pivot, tilt, and move the motor and transmission every way imaginable. The transmission mount has been loosened off to allow more movement.

When I say that one mount is still off by a mile, I mean just that. We’ve jacked the motor back up and removed both the frame stands/supports as well as the motor mounts themselves to make sure everything was assembled correctly. I’ve even taken the clamshells back apart to make sure the inserts are installed correctly. The inserts are identical to what every other Camaro owner has installed (there’s a nice thread with pictures on LS1tech), and are assembled correctly according to the Prothane instructions and other owners’ installation pictures.

Has anyone ever had this much trouble out of polyurethane mounts? We typically beat the book fairly easily at our shop (we have a tech that has spent 30+ years doing nothing but motor and transmission replacements). That tech and I spent all afternoon trying to get both mounts lined up before finally giving up for the day. As he said, “Thank God this isn’t a customer’s car.”

We’re both really, really frustrated, and even so because both of us do this for a living and considered this kind of job to be a walk in the park. At this point, I’m starting to wonder if I didn’t get some mounts that were mislabeled, or that maybe weren’t made correctly. I’ve looked all over Google, and it seems like almost nobody is having the level of trouble we’re having. I know my car has been wrecked, but it was put on a frame machine and professionally repaired back to GM specs.

Bottom line—has anyone ever experienced this kind of frustration with these polyurethane mounts? Thanks in advance for any advice, comments, etc!

97camaro383

I got my clam shells out and new mounts put in them, in a hour or two ill try to put them back in ans let you know how it goes. So far its a bit of a PITA, the long tubes are a pain to work around.

RealDealZ28

I'm really glad I don't have headers to work around. Let me know if you have any luck--I'm about to try again on my car.

Marc 85Z28

Mine were a PITA, and I had my entire engine and k-member assembly separated from the rest of the vehicle. With the drivers side mount installed, all bolts loose, even the stands, I had a friend pry on the engine with a huge bar to line the passenger side mount up - again, with the stand mounting bolts loose. Once I got the through bolt in, everything was tightened.

RealDealZ28

We got them installed around an hour ago. Using two pry bars, we got the mount close to lining up to the frame stand. Then, using an air ratchet, we forced the bolt through (similar to how some people grind the tip of the bolt to a point--it's the same principle).

I'm glad they're finished, but believe me, I never want to do another set!

johnny6

The joy of installing Prothane mounts! I also had to use pry bars but it was still a pain, enjoy the chassis vibrations Everything rattles in my car now.