Hey guys, well, almost done putting the top end back together after a head(s) swap. I have been spinning the motor over by hand while checking for pushrod length and now I am ready to set the lash. Since the lifters have bled down, how do I set lash? I was hoping to get pretty close with a "cold" lash setting and if needed, would do an engine running lash setting but I want to make sure I get in the ballpark before I start the motor. Any ideas would be great, thanks!!

 

The springs within the lifters should push the lifter pistons to the top of the lifter (flush with the lock clips). Here is a good article on some hydraulic lifter theory and procedures on adjusting the O-lash and setting the preload.

WD

Hydraulic Lifter Pre-Load Adjustment

What is Hydraulic Lifter Preload? Mechanical cam designs require a running clearance or valve lash; hydraulic lifters are just the opposite. When the rocker arm assembly is properly adjusted, the pushrod must take up all the clearance and descend into the hydraulic lifter, causing the pushrod seat to move down by .020 to .060. The distance that the pushrod seat moves down away from the retaining lock is the Lifter Preload. The hydraulic mechanism requires this precise amount of preload for it to do its job properly.

What happens if the amount of Hydraulic Lifter Preload is wrong? If clearance exists between the pushrod and the seat in the hydraulic lifter, after the rocker arm assembly has been adjusted, you will have no lifter preload. In this case the valve train will be noisy when the engine is running. All of the hydraulic force produced by the lifter will be exerted against the lifters retaining lock, and this could cause the lock to fail.

If the opposite occurs and the pushrod descends too far (more than .060?), then you have excessive lifter preload. In theory, a hydraulic lifter can pump up whatever preload you put into it, therefore with excessive preload, as the engine RPM and oil pressure increases, the hydraulic mechanism will pump-up the pushrod seat. This will cause the valve to be open longer and lift higher. This will decrease the cylinder pressure, lowering the performance of the engine. If the preload is excessive it may cause backfiring from the engine.

Methods to Adjust for Proper Hydraulic Lifter Preload
Hydraulic Lifters Can Be Adjusted at Any Engine Temperature Since hydraulic lifters can compensate for thermal expansion of the engine, the adjusting can be done with the engine cold; hot adjustment is not necessary. Adjusting Hydraulic Lifters for Proper Preload: In order to adjust the preload the lifter must be properly located on the base circle or Heel of the lobe. At this position the valve is closed and there is no lift taking place. You will need to watch the movement of the valves to determine which lifter is properly positioned for adjusting.

1. Hand rotate the engine in its normal direction of rotation and watch the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinders “intake” rocker arm. (Why? Because when the exhaust valve is just beginning to open, the intake lifter will be on the base circle of the lobe, the correct position for adjusting the intake.)

2. Back off the intake rocker arm adjuster and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the pushrod seat up against the retaining lock if you give it time to do so. (If you are installing brand new lifters they will be in the neutral position when they come in the box.)

3. Now spin the intake pushrod with your fingers while tightening down the rocker arm. When you feel a slight resistance to the turning of the pushrod, you are at Zero Lash. Turn the adjusting nut down one quarter (1/4), or one half turn (1/2) from that point. Lock the adjuster into position. The intake is now adjusted properly. Most high performance applications use ¼ turn.

4. Continue to hand turn the engine, watching that same intake. It will go to full open and then begin to close. When that intake is almost closed, stop and adjust the “exhaust” rocker arm on that particular cylinder. (Again, when we see the intake almost closed, we are sure that exhaust lifter is on the base circle of the lobe.) Loosen the exhaust rocker arm and follow the same procedure described before in steps 3 and 4 to adjust this rocker arm.

5. Both valves on this cylinder are now adjusted, and you can move on to your next cylinder and follow the same procedure again.

Do Hydraulic Lifters Need to be Primed with Oil? Many people mistakenly believe that hydraulic lifters must be soaked in oil overnight and be hand pumped up with a pushrod before installing into a new engine, this is not necessary. In fact, this could cause the lifter to act as a solid and prevent obtaining proper preload.

 

Great read, thanks! I did notice my lifters returned to the retaining lock but wasn't sure if this would still be alright. Since my intake is still off, it seems to me that I could actually set the lash with the #1 and #6 cylinder method and double check by ensuring the lifters are at the top against the retaining lock, right?

 

I would be sure and follow the procedure above for each cylinder intake and exhaust valve. I'm not completely sure the "quickie procedure" will ensure all lifters are on the base lobe.

WD

 

I was thinking the same thing. Since I have the intake off, I opted to do one cylinder at a time and watch each stroke so I'd know that both lifters were on the base of the lobe. It was a little more effort turning it over by hand but worth it. Thanks again! With any luck, I'll post the whole story in a few days.........

 

Its a lot tougher them it may seem if lifters are bled down the best thing to do is to have the intake off so you can see the pushrod on the lifter. Makes it easier to tell if you over tightened rocker.

 

That is not an issue. Once you release the rocker preload, the internal sping in the lifter pushes the lifter piston to the top of the lifter lock clip.

WD

 

good info, thanks for posting it.
Kory

 

Exactly!

ALL my lifters were collapsed when I set my lash because I took them all apart and cleaned them. It's easy to do then, because you can do it with your fingers if you had to!