Valve Adjustment, 2004 3.0

[ronaldreagan]

I have a 2004 Mercruiser 3.0 and that I rebuilt. Ever since, the engine pings / knocks. When I put the engine back together, I adjusted valves per the service manual. The timing has been adjusted, carb rebuilt, and high octane gas was used to try and work the pinging out and none of these were the solution.

After checking the compression again, I get 120 psi on each cylinder. Tonight, I took the valve cover off and spark plugs out, loosened the rocker arm nuts at each cylinder 1/2 turn increments and checked the compression in between increments. The compression improved to 135 psi on the first 1/2 turn, then 150psi on the second half turn.

The concern is when I check the rod play at the recommended engine position it seems so excessive that I would not want to run the engine unless I knew it was adjusted properly.

Here are the two questions:
- How do I adjust the valves on a Mercruiser 3.0?
- Could bad valve settings cause the pinging / knocking?

Any advice on properly adjusting the valves would be great!

 

[Paintman1960]

Many vids on adjusting valves. I suspect you don't have it right , yet !
But you will get there...

 

[ronaldreagan]

Many vids on adjusting valves. I suspect you don't have it right , yet !
But you will get there...

This the best explanation on the mechanics of hydrolic lifters so far....

Makes sense how they can get over tightened. Also makes me wonder if my lifters are operating correctly.

 

[ronaldreagan]

Okay... I meticulously followed the Mercruiser procedure again and the compression went back to 120psi across all cylinders again.

Thinking I still didn't get right, I took off the side plate to inspect the lifters and confirmed that they were in the right position when adjusting. Rod just snug against the lifter, then one 1/2 turn to preload the lifter. Again 120 psi across all cylinders.

Loosened a 1/2 turn, 135 - 140 psi compression.

Does anybody know what's going on here?

 

[1960 Starflite]

Okay... I meticulously followed the Mercruiser procedure again and the compression went back to 120psi across all cylinders again.

Thinking I still didn't get right, I took off the side plate to inspect the lifters and confirmed that they were in the right position when adjusting. Rod just snug against the lifter, then one 1/2 turn to preload the lifter. Again 120 psi across all cylinders.

Loosened a 1/2 turn, 135 - 140 psi compression.

Does anybody know what's going on here?

I have rebuilt a few Chevy small blocks. I only use the method you have done to set lash to zero + 1/4 turn. Final adjustment is made (Me) with engine running. I altered a valve cover by cutting a slot out at the adjustment nut area.
With engine running loosen each nut until clack is heard (one valve at a time), tighten until rocker is silent. Tighten 1/4 turn, engine will stumble a little, then 1/4 turn more. I never had much luck with the 3/4 turn thing with small blocks.
I used the same method with my 140hp 3.0L in my Century. Little messy but "it is what it is" with valve cover off.

 

[alldodge]

Your going past zero lash. Zero is where there is no up/down movement of the push rod, rotating is not in the mix. The weaker the lifter is, the more sensitive your fingers need to be to find zero

Try the running method that 1960 mentioned

 

[Lou C]

agreed the tricky part is determining zero lash. When I replaced the heads on my 4.3 I used the zero up and down on the pushrod method + 1 full turn. And got 160-165 compression numbers.