ARP: Perma-Loc® Rocker Arm Adjusters

Readjusting the locker arms on your performance engine just got a lot less irritating. ARP’s patented Perma-Loc® adjuster is the first “poly lock” on the market that you don’t have to continually tighten. Perma-Loc® achieves this feat in a few ways.

First, the adjuster body is heat-treated all the way through—not just case-hardened—eliminating the thread “movement” common to other products.

Second, the threads are machined perpendicular to the bottom of the adjuster, so it seats evenly and applies pressure in 360 degrees.

Last, the set screw is machined flush on the bottom (not pointed), producing optimal contact on the rocker arm stud.

Perma-Loc® is also easy to use: ARP designed the compact 12-point head to hold your wrench in position while you lock the set screw with an Allen wrench—no special adjusting tools necessary.


  • First “poly lock” on the market you don’t have to continually tighten
  • Heat-treated 8740 alloy chromoly steel achieves 190,000-psi tensile strength.
  • Bottom machined perpendicular to the threads
  • Threads precision-machined for maximum engagement
  • Locking set screw ground flush with the rocker arm stud
  • 12-point head holds the wrench to eliminate the need for special adjusting tools
  • Patent #5,323,741

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Though this is not a paid review, this content has been produced by The AAM Group™ in support of manufacturers with whom it has a business relationship.

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