Heat Riser - Before I burn a valve...

[davepl]

I noticed that even fully warmed up (hot, actually) I was still getting most of my exhaust out the driver's side pipe.

I checked and the heat riser is -just- on the edge of closing. If you blip the throttle, it's enough to open it further. So it's just balanced against the spring pressure.

I expected, however, that by this time it'd be fully open.

Does the thermal spring on them work to close the valve, and just does less once hot? Such that they require the exhaust flow to actually do the work of opening it?

I didn't boil the fuel, but I got to the tick before H on the temp gauge idling with the AC on, so I really don't need to be forcing exhaust through the crossover at full temperature!

Anyone old enough to remember how they're supposed to function?

(Please don't tell me to remove it, as it serves an important driveability function. I just want it to work right).

Thanks!