Very little resistance? Check all of your rocker arms to make sure you didn't spit a lifter out. There are only so many things that cause a sudden loss of oil pressure while running.
1) twisted tang on intermediate shaft (isn't that) 2) oil filter rupture (isn't that) 3) cracked pickup tube (probably not, I've seen two of these fail in my entire life) 4) pushrod/rocker failure and loss of lifter (???)
"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
