[68 Firebird]

I had a neighbors son stop over last night and wanted to test a timing
light he was doubting. Well we headed out to my garage for a beer and
hooked them both up to my Firebird and fired them her up. It was 30 degrees.
outside and car was run earlier in the week.

She went right to high idle at 1400rpms and after 30 seconds I tapped
throttle and she dropped to 1200rpms as usual. After another minute
or so the idle had climbed back up to 1350 and I again tapped throttle
and she dropped down to a 775 curb idle. Again as usual.

Both timing lights gave exact same results the whole time. for timing
and rpms. Flash was steady at high idle and curb idle.

Just as the thermostat was initially @185 opening I watched the rpms drop
down to 650 or so and the motor shuddered for a few seconds and then
recovered slowly to 800rpms. We watched it run for another 15 minutes and
it seemed it only did it once on the initial opening of stat. Just seemed odd
to me. With a 180 stat and iron heads is this normal.

I rarely run it like that, normally stat is opening as I am driving so I would never notice.
Can a drop in water temp effect a motor that fast when stat first opens?



Gerry