Setting the Valve Lash on a 1998 Gen VI 454 Engine

[San_Diego_SeaRay]

So page 3A-24 of Manual 16 says that "No valve adjustment is needed. Simply torque the rocker bolts to 45ft lbs and that sets the lash". Is it really that simple? No "spinning of the engine"? Just torque each rocker arm to 45 lbs?

Other online resources like THIS GUY indicate that you should spin each push rod until it doesn't move freely, then you tighten the rocker stud another 1/2 to 3/4 of a turn. How many of you use this method? Do you use 1/2 or 3/4 turn?

I thought the guy in the video had an awesome trick that would simplify this process. But then I read the Merc manual. Well they simplified it even more if all I gotta do is torque to 45 lbs...

 

[scoflaw]

Best way to check lifter preload on a non adjustable valve train. Rotate your crank to position your lifters/valves like they were adjustable. Tighten nut to 0 preload, then it should take about 3/4 of a turn to get to the 40# spec.


















rotate your

 

[alldodge]

So page 3A-24 of Manual 16 says that "No valve adjustment is needed. Simply torque the rocker bolts to 45ft lbs and that sets the lash". Is it really that simple? No "spinning of the engine"? Just torque each rocker arm to 45 lbs?

Other online resources like THIS GUY indicate that you should spin each push rod until it doesn't move freely, then you tighten the rocker stud another 1/2 to 3/4 of a turn. How many of you use this method? Do you use 1/2 or 3/4 turn?

I thought the guy in the video had an awesome trick that would simplify this process. But then I read the Merc manual. Well they simplified it even more if all I gotta do is torque to 45 lbs...

Apples and Oranges

He is discussing adjusting valves which require 3/4 pass zero lash, and your motor (and others) require 40ft torque and no measurement of zero lash. Two different designed motors

 

[San_Diego_SeaRay]

Apples and Oranges

He is discussing adjusting valves which require 3/4 pass zero lash, and your motor (and others) require 40ft torque and no measurement of zero lash. Two different designed motors

Gotcha. So do I just go down the line and tighten each rocker bolt to 45lbs? Regardless of where each valve is in the compression cycle?

 

[alldodge]

For a 1998 454 Gen VI yes, 40 ft lb not 45

 

[San_Diego_SeaRay]

For a 1998 454 Gen VI yes, 40 ft lb not 45

Thank you!

 

[scoflaw]

If the block was decked, heads were shaved or the seats were reground, check your clearance like I posted in #2 post. It's possible that your valves won't fully close because now the pushrod is longer than it should be.

 

[San_Diego_SeaRay]

If the block was decked, heads were shaved or the seats were reground, check your clearance like I posted in #2 post. It's possible that your valves won't fully close because now the pushrod is longer than it should be.

Great point. Yep, I'll have to pay attention to that when reassembling. I'll do a compression test to see if there is or are weak cylinder(s). Heads were shaved and valves ground. Block was not decked.

 

[Lowlysubaruguy]

One simple way to check for lash adjustment that it to tight keep in mind this is not checking for proper clearance it will just show a valve that is for sure to tight. Rotate the engine at least two full turns if you can disable the ignition and spin it with the starter crank it ten seconds. Let it sit half an hour. Turn the crank until an intake or exhaust valve is close to half way open on a given cylinder you should be able to spin the push rod with your fingers on the opposite rocker. If it’s got some resistance that’s ok if it’s tight it’s most likely to tight. While this isn’t 100% accurate it’s a simple test if all of your push rods spin with minimal resistance there in my opinion not to tight on the other hand if you have hydraulic lifters and any of them have play then you have to much clearance or a failed part which could be a variety of things from the cam to the valve or valve seat. So this is. Very good and simple procedure to do. A valve that is only a couple thousandth to tight will not show in a compression test but will run poorly so a compression test won’t tell you if your lash is just off a little. There are exceptions some lifters require up to 24 hours after an adjustment has been made while I cant say I’ve ever seen this on a larger v8 some small car engines 1.0 to 2.0 liter sizes with very light valve springs wont bleed the lifters down without sitting a geo metro is one for sure just an example