When should lifter preload be checked (new engine)

[Landon427]

I'm hoping someone can answer what is probably a pretty basic question. When should lifter preload be checked when a new engine is being put together? on my '99 2.5L, I have installed the new Johnson Hylift lifters (I did not pump them up with oil, or soak them with oil). I'm wondering if I check lifter preload in this state or after pre-oiling the engine through the distributor hole?

Overall I think lifter preload will be about 0.012" less than it was, from block/head machining, head gasket thickness differences, old vs new pushrod length differences etc, and I'd like to check it to see if I am in range (0.02" - 0.06"?).

Thanks for any advice.

 

[BlueC]

Overall I think lifter preload will be about 0.012" less than it was, from block/head machining, head gasket thickness differences, old vs new pushrod length differences etc, and I'd like to check it to see if I am in range (0.02" - 0.06"?).

If you're working with hydraulic lifters there is no lash to measure and set, you just snug them up (0 lash), then add 1/4 to 1 full turn. What does the book say?

 

[Wildman]

Have you looked at the FSM?

https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/

 

[Wildman]

Here's what AI says:

AI Overview

The 2.5L Jeep engine uses hydraulic lash adjusters, meaning the valves are not adjustable in the traditional sense. Instead of shims or tappets, these engines rely on hydraulic pressure to maintain proper valve clearance. If you're experiencing valve noise or other issues, it's likely due to wear in the rocker arms, lash adjusters, or an oiling problem affecting the valve train.

https://4wdmechanix.com/jeep-232-25...traight-four-valve-clearances-and-adjustment/

 

[Landon427]

Have you looked at the FSM?

https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/

The FSM says nothing about checking lifter preload, at least not that I could see.

 

[Landon427]

Here's what AI says:

AI Overview

View attachment 625067

The 2.5L Jeep engine uses hydraulic lash adjusters, meaning the valves are not adjustable in the traditional sense. Instead of shims or tappets, these engines rely on hydraulic pressure to maintain proper valve clearance. If you're experiencing valve noise or other issues, it's likely due to wear in the rocker arms, lash adjusters, or an oiling problem affecting the valve train.

https://4wdmechanix.com/jeep-232-25...traight-four-valve-clearances-and-adjustment/

As I understand it, lifter preload is only adjustable using different length pushrods on these engines. There might be a way to shim the pedestals somehow (in the case of too much preload) but I haven't heard of it. I'm just trying to establish when I should check lifter preload since some things have changed during the rebuild. It could well be that I don't need to worry about it, but this engine came down for rebuild due to a knock and the source was not found, so I'm trying to be careful to check whatever I need to as it goes back together.

 

[BlueC]

The FSM says nothing about checking lifter preload, at least not that I could see.

It likely says to snug the rocker to the valve tip, then tighten 1/2 turn, or something similar. Pretty standard with hydraulic lifters. The internal spring takes care of the rest.

As I understand it, lifter preload is only adjustable using different length pushrods on these engines. There might be a way to shim the pedestals somehow (in the case of too much preload) but I haven't heard of it. I'm just trying to establish when I should check lifter preload since some things have changed during the rebuild. It could well be that I don't need to worry about it, but this engine came down for rebuild due to a knock and the source was not found, so I'm trying to be careful to check whatever I need to as it goes back together.

You mentioned things are maybe .012 shorter, the hydraulic lifter has more than enough room to soak that up. Don't worry about that tiny amount, tighten the rockers and move on.

If you had mechanical (solid) lifters, then you would need to adjust for that .012 difference, which involves measuring and setting lash, potentially buying new shorter push rods.

 

[Wildman]

The FSM says nothing about checking lifter preload, at least not that I could see.

As I understand it, lifter preload is only adjustable using different length pushrods on these engines. There might be a way to shim the pedestals somehow (in the case of too much preload) but I haven't heard of it. I'm just trying to establish when I should check lifter preload since some things have changed during the rebuild. It could well be that I don't need to worry about it, but this engine came down for rebuild due to a knock and the source was not found, so I'm trying to be careful to check whatever I need to as it goes back together.

As BlueC said above if things were only milled to make everything flat then the lifters will compensate for that. Because the 2.5 uses a pedestal to mount the rocker into as far as I know there isn't any adjustment available & if I remember correctly you just torque the rocker down & that is it. The only time you'd set valve lash on a hyd lifter in this type of engine would be if you had adjustable roller rockers like from Harland Sharp.