My new dropped header

It doesn't seem to heat any faster, though the indirect tank gets satisfied more quickly it seems. Perhaps that was due to scraping some of the crud off the combustion chamber. I have a cleaning & combustion test scheduled for Dec 20th, earliest they had. Ed mentioned it could be all the sawdust (and there was a lot over 3 years) that settled in the basement getting sucked into the intake. Suprised there are no air filters on the burners.

The steam timing from dead cold is as follows:

9 mins- header heated
13 mins main starts heating
18 mins long return hot
21 mins short return hot
25 mins 1st section in all rads hot

One interesting thing, rear tapping made steam 3 mins before front.

Looks like I need more main venting. Header isn't insulated, mains are 90% insulated, risers to each rad are not insulated.

I've been skimming it a bit each night and the floating oily crud is gradually going away. However there's still a ton of crud that gets kicked up when the burner fires, turning the water solid dark brown. Should I flush the whole thing or will the crud eventually settle?

jim