Mazdaspeed Motorsports Development shim-under-bucket style solid lifters can be used to upgrade NA (HLA = Hydraulic Lash Adjuster) or NB (solid disc-over-bucket) valve trains.
The first image below illustrates the various valve train setups. The second image shows the catastrophic damage to the head that happens when an NB disc-over-bucket style disc is “spit out.”
After a fresh valve job is completed, assemble the valve train and use stacked feeler gauges to measure the lash (the gap between the top of the lifter and the lobe of the camshaft) of each lifter. Cold lash clearances (with caps installed) should be:
INTAKE = .20mm (.008”)
EXHAUST = .25mm (.010”)
Once the needed thickness(es) are known, order Supertech lash caps. List the needed sizes in the notes field when you check out.