88 Mercruiser 3.0 Valve Adjustment

[snowman246]

I am putting my 3.0 back together (full rebuild). I want to refresh my own memory on setting the valves by picking your brain. I understand TDC and which valves to set when. My question is solely aimed at removing valve lash prior to turning 3/4-1 full turn.

Am I thinking correctly, to tighten rocker nut until I cant spin the push rod equals zero valve lash? I have built a handful of this style engine but hundreds if not thousands of engines with full roller assemblies. I just want to make sure.

 

[alldodge]

Am I thinking correctly, to tighten rocker nut until I cant spin the push rod equals zero valve lash?

Ah no, you rotate the rods to make sure they are free to turn and are in the center of the rocker and lifter. Once there your move the rod up and down while turning the nut down slowly. The up/down movement is what your feeling for. Once all up/down stops, this is zero lash point

 

[snowman246]

Ok thats what I was thinking. The book I have stated when the pushrod stops spinning you are at zero lash. I knew it couldn't be right. I set them for the up/down as I have done on every other engine. The description in the book I have sucks. Just wanted to make sure the book was wrong. Thanks AllDodge.

 

[Alumarine]

Ok thats what I was thinking. The book I have stated when the pushrod stops spinning you are at zero lash. I knew it couldn't be right. I set them for the up/down as I have done on every other engine. The description in the book I have sucks. Just wanted to make sure the book was wrong. Thanks AllDodge.

The first time I adjusted hydraulic lifters I did the spinning to zero lash method.
Ended up with the valves not closing completely. Oops...

 

[Bondo]

The description in the book I have sucks.

Ayuh,.... Many manuals focus on the spinnin' of the pushrod, when the up/ down motion is what's critical,....

 

[fishrdan]

Spinning the pushrod is the correct "per-manual" procedure, but what they omit is that you need to spin the pushrod lightly between 2 fingers. Just enough pressure to spin the rod between 2 fingers, a very light touch. There is a point when you'll be spinning the rod while slowly tightening the rocker nut, and the rod will slip in your fingers - that's zero lash.

Where people get in trouble is taking the manual at it's literal words, and spinning the rod (with all their might) while tightening the rocker nut,,, until the rod stops spinning completely. By that time it's way past zero lash.

One other tip. I have had false zero lash adjustments when the socket leans over and presses against the rocker arm, causing the clearance to disappear. When the socket was removed there was still play in the push rod and the nut needed a bit more tightening.

 

[Joshto]

Sorry folks for reviving this old thread. I just replaced the blown head gasket of my 3.0 140. Adjusted the valves according to the tips here and the procedure described in 2 popular YouTube videos. Followed the steps to the letter, but I noticed that after turning the engine 360 for the second round (3 valves left), two of the 5 that I had just adjusted while cylinder 1 was in the compression stroke (piston was up so I think is the compression) became loose.

is it possible the piston was up but it wasn't the compression stroke? What method should I follow?