Valve adjustment, not a mopar

Yeah, it's not a Mopar, but I have a question about valve adjustment on a 97 GMC 350 v-8, 89,000 miles.

It's a friends truck, and he asked me to look at it because of some loud lifter/rocker noise on a cold startup.

I removed the left side valve cover and the #4 cylinder intake rocker was very loose. I followed the procedure to adjust the valves: TDC for the cylinder when it should be firing, and tightened the bolt to zero lash, then 1 additional turn. While doing this, I thought to my self that this is too tight. When I started the truck, it was too tight, the engine missed terribly and set the check engine light blinking immediately. The valves were not closing completely

Would the lifters eventaully have bled down to allow the valves to close?

I didnt let it run more than a minute, removed the valve cover and readjusted the rockers to zero lash, and no more turns. It's quiet now. Does anyone have any experience with this?
Author: admin