Finally got the shock insert free of the housing.
I did several heat and cool cycles while soaking with a mixture of acetone and ATF. Found the acetone a bit too volatile for use with the heat gun, and changed to brake fluid for a few cycles. Applied tension to the shock rod by screwing the top nut down on 2? nominal PVC pipe. No joy.
I ended up connecting the shock rod to my engine hoist with a heavy duty carabiner. Restrained the cast housing below the engine hoist legs with a square steel tube and a flat nylon sling. Took a few tries to get the awkwardly shaped housing tied down so the rod tension was pretty close to straight and there was no danger of crushing or bending anything. I also added a second sling to prevent the casting hitting the floor if and when the shock insert finally popped free. Placed a foam mat under the casting just in case.
Applied so much tension I thought the sling was going to break (it actually did once, and I think they are rated to a couple of thousand pounds). Left it soaking for several hours with tension applied, while periodically beating on the shock rod to hopefully move things around a bit. Worked up the guts to add even more tension, and it finally popped. There was enough corrosion product on the outside of the shock insert that it only came half way out rather than dropping the casting to the floor.
The learnings from this experience are to make sure the bearing housing sleeve is filled with oil or antifreeze to prevent corrosion (mine were not filled).
If you can?t get the insert out with a modest pull, come up with a way to apply a Hell of a lot of tension without bending or crushing anything; the PVC pipe I had to hand was inadequate, the acetone would dissolve it. I considered using 2? iron pipe, but I would be concerned about breaking or distorting the spring perch with this method.
Thanks for all the suggestions. I was really running out of patience on this one, which is never a good thing around the Lotus!
Stu
Here are a couple of pictures.