I also thought about just changing lash pads so I did so and was able to get the right clearance. However this is still just a temporary fix.
Lucky this is Rons motor and not mine. He said head get it all checked out and maybe fixed if it can be. I told him to go with bigger valves! Ha
I'll only drive my truck a day like this.. I hope.. I'll take this head off tomorrow after work and slap on the other u67 'one intended to go on lz23' drive it this way tell everything is needed to put the Lz in the 521..
