I'm waiting for UPS to deliver my leak down tester. I realized that I performed the compression test with the throttle closed. I repeated it today, holding the throttle open. Essentially same results with higher numbers.
1-200, 2-unable, 3-215, 4-210
5-190, 6-190, 7-unable, 8-210
I also measured the outside dimensions of the "box". It is 12.5x10x4 inches. This calculates to 500 in3, which is 8.66 US liquid quarts to completely fill the box. I'm not sure how thick the steel of the pan is, but I'd guess it doesn't subtract a ton. Add the pickup mass, lets say 8 quarts fits inside the box of the pan.
[Crazy useless math]
The bottom of the box is 8 inches below the centerline of the crank. That makes it 4 inches above the top of the box. Stroke on the 408 is 4 inches - half that to get 2 inches down travel of the crank. Since the box 4 inches tall and 8 inches below the centerline, that means the top of the box is 2 inches below the bottom of the crank stroke (center of rod journal). Rod journal is 2.311. Half that is 1.65ish. Add another half inch for the rod cap and bolts. Make that 2.2 inches. So the crank and rods extend 0.2 inches into the box. Add one inch space, that means I can only have 4 - 1.2 = 2.8 inches of
oil in the box. That is 6 quarts of
oil. That seems pretty close to the "7 quart SYSTEM" - 1 quart for filter and the internal
oil passages = 6 quarts added at oil change.
[/Crazy Useless Math]
So, I guess I should add 6 quarts to an empty pan, then mark the dipstick from there. (One quart down on this pan equals about 1/2 inch.)
I will post the leakdown test when I get it done.
Should I do the leak down test on a cold or warm engine? I think a warm engine would be more accurate, but don't want to burn my fingers on the headers.