I do block them. Always have.
The molly paste assembly lube used for cam break in will plug the filter soon after you fired up the new engine. You should follow the directions regarding the cam break in procedure then change the oil and filter after about 1 hour while still warm. That gets the metal crud and molly paste out of there. The rings will not like the molly paste while trying to break them in so it needs to come out as soon as possible after the cam is broken it. After that, you should not have problems with low oil pressure. If it does affect your oil pressure after the first change, your oil was not being filtered anyway [img]graemlins/clonk.gif[/img]
Think about it another way. If you leave it alone you will still quickly plug the filter with the molly paste and the bypass will do its job and open. Now you are breaking in a brand spanking new engine using no oil filter at all.
All those metal particles are just being pumped right back into the oiling system and continuously recirculated. That can't be good.
If you plug it, you will always have filterd oil. During the break-in process you may see lower pressure on the gauge but at least the oil is still getting filtered. After the initial oil change, you should not have low pressure issues any more. If you see low pressure on the gauge after the initial break-in, you need to check the filter as it may be dirty. If not, you have other problems. The engine is not under load during cam break in and the pressure is not in the danger zone.
Loose that Fram filter. They are not the best. Try a Wix or Purolator. They are much better.
Just my opinion. [img]smile.gif[/img] Your results may vary but I want you to have both sides of the story.