Re: L35 Rocker Arm Issue
Copied from another discussion Matching the right cam with the right lifter and adjusting the valves correctly is important in order to avoid noisy lifters at startup, a problem that's commonly known as "morning sickness." Prior to '92, the 262 had the traditional adjustable rockers that had been used on all of the small block Chevys for years. The cam had a 1.380"/1.335" base circle and used a short-travel lifter. Turning the rocker nut one turn gave the lifter a .040" preload and put the plunger in the middle of its travel.
In 1992, when Tonawanda switched to a "net lash," non-adjustable valve train, the base circle was reduced to 1.260" on all of the cams and a lifter with more travel was used across the board, apparently to provide more latitude for manufacturing tolerances with the "net lash" rockers. (Note: The Romulus plant did not switch to "net lash" until '95). Unfortunately, this combination can cause noise problems in the field because it takes longer for the lifter to refill at startup when it has bled down overnight, unless the preload is set at .080".
This problem can be cured by turning the rocker nut two turns with the adjustable rockers, but that can't be done with the "net lash" setup, and it's contrary to everything everybody knows about setting the valves on a Chevy, too. The best approach requires the replacement of the "net lash" studs with a set of special conversion studs that have metric threads on the bottom, along with 3/8" threads on the top, and using them along with the short lifters that are preloaded one turn. Pioneer offers this special replacement stud.
If you prefer to rebuild the engines as they came and use the longer lifters with the adjustable rockers, increasing the preload to two turns will help avoid "morning sickness." Carefully controlling the stem heights and clearances with the "net lash" rockers will help ensure that you have enough preload to avoid noisy lifters most of the time.
Just for the record, there's one extra benefit to switching to the short lifters and the adjustable valvetrain on everything; you can disregard the base circle issues and consolidate more of the cams.
