Strange Slant 6

The last day of school last year my sons slant 6 went from running great to running awful. Had to first gear every hill, would not idle, and went through four quarts of oil in 15 miles, with hardly any smoke at all.

Anyway we now have a crate motor to put in it and I have a question. The other day I unbolted the tailpipe from the manifold, and the front end of the tail pipe is as white as cotton inside. Does it mean anything?