Reply to "Cooling and ignition advance"

...So went to buy a temp gun to test idle temps. It was 60degF outside, so it wasn't real acid test, but learned something.

My 71 has Fluidyne rad with two temp switches, and only one is connected, and it switches the other of the flex-a-lite dual fans. The other fan is manual. Thermostatically controlled one was connected to upper switch, which is 82/77 and I think the lower one is the same because the switch on temps measured from engine were about the same.
I tested both and the difference was that the upper one switches off at about 195 deg measured from engine to coolant bottle steel line and the lower one doesn't switch off until engine is about 180-185deg (I was little late measuring, tested with both fans on). It makes sense, because upper switch sees coolant that has been cooled in the radiator already, therefore switching off earlier. The lower one has to see a real temperature drop in the incoming line.

The car was static when I did this and I found that in the lower position the fan would run continuous until I'd begin to drive, letting the engine temp fluctuate less. I decided to use the lower.

Then I measured the temps with my relatively hi initial advance and ported vacuum vs. manifold vacuum. I had to do this at 1000rpm, as I couldn't get revs lower with manifold vacuum. (I might have been able to, by removing my vac secondary holley and adjusting the secondary idle position. I did not check if there was adjustment left to close the blades.)

I got 197deg stable with manifold vacuum, and 201 with ported. It's hard to say exactly, but there was some difference.
Ported at 800rpm gave 199deg.

I did not notice that the idle speed would have wanted to "stick" like what happened in my Mustang. Mustang has much more radical engine...

Did not yet test drive to see if manifold vacuum would reduce the hi gear, low rpm, acceleration pinging. My guess is it wont, but I've been wrong before, so I'll test.