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149-186 Holden Rocker Geometry & Lifter Adjustment

The principle for adjusting a hydraulic lifter is the same regardless whether they can actually be adjusted or not dependent on the rocker fulcrum design. The objective is to ensure the push rod socket is pushed into the lifter a predefined distance that will allow the lifter to automatically take up zero clearance in the valve train for the life of the engine. (I have an article on Hydraulic lifter operation in the Engine section, please refer to this for further explanation). The ideal setting of 50 yrs ago was approx .030" to .050" of plunger movement into the lifter equating to 1/2 to 1 turn of the fulcrum nut after zero lash, but can be much more these days because the cylinder head would have been machined several times which means the head sits lower and therfore the pushrod sits higher, but we still are adjusting the lifter the same amount after zero lash. With lifter pump-up (which by the way can happen even at .030" adjustment) you will lose compression and the engine may stop and won't restart until the lifters bleed down. So the safer option has been to stick a little closer to the loose side rather than the tight side. What some people don't understand is that to get lifter pump up, there has to be something wrong with the current set-up ie. valve spring pressures, mismatch of valve components. With the correct parts matched to the camshaft, lifter pump up can onlt occur if the engine is revved past it limit. The engine used is a Holden 149-186 which utilises an adjustable rocker fulcrum , one for each valve. The method I show in the video is for adjusting the rocker geometry and as a consequence the lifter is also adjusted albiet not as you may think. After adjusting the geometry if you feel the need to adjust the hydraulic lifter to retain the original plunger depth, then you have to change pushrod lengths. Since this is an expensive way of making adjustments, it is rarely to never done on a stock engine. However if you unsterstand how a hydraulic lifter works, you will not be bothered that the plunger sits deeper in the lifter body. The following video covers exactly what dimensions we are chasing for correct geometry and at the same time covers off on lifter adjustment.

 

The table below shows the relationship of how far the push rod socket is pushed into the lifter at various turns of the fulcrum nut on a Holden 149-186 after achieving zero lash. This is for a 3/8" UNF stud that has a pitch of .041" per thread. If your stud is a different size then you will need to know the pitch to calculate what is required to adjust for one quarter turns of the nut. The formula for a 1:1.5 ratio rocker is calculated by multiplying the nut movement distance by 1.68 as calculated by my CAD program.

Turns of fulcrum nut

Fulcrum movement

Lifter plunger movement
1/4 turn

.010"

.016"  (.40 mm)       
3/8 turn

.015"

.025"  (.63 mm)      
1/2 turn

.020"

.034"  (.86mm)      
3/4 turn

.030"

.050"  (1.27 mm)      
1 turn

.041"

.069"   (1.75 mm)    
1 1/4 turn

.051"

.086"  (2.18mm)      
1 1/2 turn

.061"

.102"  (2.59 mm)   
1 3/4 turn

.071"

.119"  (3 mm)   
2 turns

.081"

.136" (3.4mm)

 

Please Note:  The maximum plunger travel may vary between lifter brands. You need to test the maximum travel by pushing the plunger in until it bottoms out and record the distance travelled. Then set the maximum distance to 80% of that. This will avoid getting to the stage where you may get a solid lifter. The lifter I was using had 4mm travel, therefore 2 turns would be the max I would want to adjust the lifter. If the geometry calls for a deeper measurement then you will have to get shorter pushrods or fit valve caps.