'87 Shelby CSX
#321 of 750
davidr at shelbycsx.com
Making Solid Polyurethane Motor Mount Inserts
Although polyurethane motor mount inserts are available from a number of vendors for many different cars, Chrysler turbo cars are not on the list. I set out to "roll my own" from raw materials.
After consulting with an engineer at Gallagher Corporation about the properties of various polyurethane compounds, I picked one and bought a 2"x3"x12" raw bar of their GC480 compound. The compound has an 80A durometer rating and is slightly firmer than the original rubber. Gallagher's engineer said this compound should have about a 10-year life in this application.
I carved out a piece to replace the rubber in a stock insert. A hunk of polyurethane this thick is tough to cut! I tried various hand and power saws without much luck. Power sawing generated enough heat to start melting the block. I ended up using a sharp new utility knife and a lot of muscle and patience.
Separating the rubber from the metal insert is another thing I don't look forward to doing again! I cut out what I could and ended up burning the rest out. There's probably a better way, but none of the solvents I have on-hand would affect the rubber at all.
But, after all the work, the result looks very nice. After I pressed the polyurethane into the metal frame, I gave it all a shot of satin black trim paint. With new AutoZone pieces furnishing the metal parts, and with the raw polyurethane, the cost of materials comes to about $20-$25 per insert. The polyurethane is available from Gallagher in 12" increments. A 12" bar is enough to make five inserts.
UPDATE 9-12-01 -- The solid inserts definitely keep the motor from moving, but there was way too much vibration for my taste. It would be okay for race use, but not in a daily driver. A softer polyurethane compound might work. I ended up replacing the solid inserts with a set of stock ones. To keep them from dying an early death, I stuffed a piece of polyurethane in the large hole on each one.