<http://findarticles.com/p/articles/mi_m0BQH/is_6_49/ai_n16547364>

http://findarticles.com/p/articles/mi_m0BQH/is_7_49/ai_n26972065

Engine oil filters : technical and empirical evaluations of anti-drain back systems and element tubes</a>
Outdoor Power Equipment, June, 2006, by Paul Dilger, parts 1 and 2

Unfortunately the articles have the photos omitted, bit it is interesting none the less.

Todd
'88 Westy