adjusting valves 3.0 GS PNCA

[aerobat]

hey gents!

i want to check/adjust valve clearance on my 3.0 and have read the according manual procedure from boatinfo.

the job seems straight forward and easy, but i do not understand one thing fully and fear to make something dramatically wrong :

the manual calls to turn the adjusting nut until ZERO valve lash and after that even turn it one full turn TIGHTER. ???

so they call for zero valve clearance ???

i adjusted valves in cars and motorcycles , but this were OHC / DOHC and not pushrods, and i never heared to adjust for zero clearance !

or is it here different so you indeed go for zero lash on the rocker and the final valve clearance is done automatically by the hydraulic valve lifters ?

can somebody clarify ?

thanks much in advance !

 

[Silvertip]

Re: adjusting valves 3.0 GS PNCA

Your engine has hydraulic valve lifters to maintain zero lash. There are two ways to do this. 1) by feel, 2) engine running. But the fact remains, if the adjustment was properly set when the engine was built, they will be properly set today. Chevy built engines have used hydraulic valve lifters since the introduction of the PowerGlide transmission in the 1950 model year cars.

By feel you turn the engine so the valves on one cylinder are both closed.
You Then loosen the adjusting nut until you can just barely spin the push rod.
Turn the adjusting nut one turn down. This sets the plunger in the lifter to the proper depth and that valve is good to go.
REMEMBER: The valve you are adjusting must be closed with the lifter on the base circle of the cam.

To do this with the engine running, cover the push rod end of the each rocker arm with aluminum foil to prevent oil from spraying all over you.
1) Start the engine
2) Loosen the adjusting nut until the lifter just begins to rattle (you no longer have zero lash at this point).
3) SLOWLY tighten the nut until the rattle just quits
4) SLOWLY turn the nut 3/4 - 1 turn more.
5) Repeat for the others.

 

[aerobat]

Re: adjusting valves 3.0 GS PNCA

But the fact remains, if the adjustment was properly set when the engine was built, they will be properly set today.

thanks silvertip ! so please lets clarify - if there is no urgent need , lets say a rattling rocker, there is no need to ever touch that kind of adjustment since the hydraulic lifters should keep valve clearance over an entire engine life maintanance free ?

 

[Don S]

Re: adjusting valves 3.0 GS PNCA

You are correct, if it's not noisy, leave them alone. If you do have one that is noisy, you might be able to turn it down and stop the noise, but that lifter either needs rebuilt or replaced.

 

[aerobat]

Re: adjusting valves 3.0 GS PNCA

ok, i learned something new about my engine. i do not have rattling lifters...

thank you gents !