Wow - 250°. I would have thought there would be problems that high. Apparently not. Good to know for future reference.
Stephan had descibed earlier how he rolled whatever he used into strings - and that's what I did.
At room temperature, I pulled and rolled the butyl into approx. 1/8" diameter strings and laid it into the grooves single file (tapering the ends of successive strings and overlapping them a little for even fill) - it's just insurance to make up for any loss of material that has been displaced - any excess will squeeze out the sides of the tongue and groove. Then I put the other half of the assembly in place so that its tongue part rested on those strings. Then I heated it into the oven and let it soak. Then I opened the oven and carefully squeezed around the outside of the tongue and groove parts (using pliers) - as it cooled a little, I put it back into the oven to heat up again, then worked them tighter together some more. Repeated until the parts were fully mated all around.
Ideally, and no doubt this is how the manufacturers do it, you would clamp the whole assembly with enough pressure to squeeze it all fully together with one heatup cycle. But it's probably more practical for the DIY'er to just work inefficiently with the pliers and repeated heating cycles.
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs
Last edited by peva; 10-07-2012 at 08:19 PM.