Manton Duramax 6.6 Adjusting Nut 12 pt. Jam Nut 10mm x 1.25 x .620 O.D.

Manton Duramax 6.6 Adjusting Nut 12 pt. Jam Nut 10mm x 1.25 x .620 O.D.

Manton Pushrods
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Similar to our custom adjusting screws for the racing market , our diesel rocker arm screws are made of H-13 tool steel that is heat treated, triple tempered and nitrided for wear resistance. This combination of materials and heat treating procedures makes the most durable and reliable screws available on the market. All of our screws are manufactured with rolled threads and broached to accept an allen wrench. Manton makes custom screws on request, available with or without oil holes for pre-lube as well as oil grooves for pressure fed oiling; Minimum quantities may apply. Depending on the style of screw and application, proper installation instructions will vary.


Duramax engines will use our part D-838 , featuring a pressure fed side oil hole. All pressure fed adjusting screws need the oil band positioned properly so oil can flow around the oil band and into the side oil hole of the screw. This is very critical due to the fact that, if not aligned correctly, lifter and camshaft failure will occur.

12 valve Cummins with stock rocker arm configuration would use our part number #D-828 , and 24V will be our part D-837. Our screws feature stock length , thread pitch and ball radius’. Cummins rocker arm adjusting screws are usually positioned with their ball 2 to 3 threads sticking out of the bottom of the rocker body. Any deviation from the stock adjusting screw position will result in changes to the rocker arm ratio, affecting lift at the valve. These instructions may vary from one engine combination to the next, so it may be a good idea to call us or the rocker arm manufacturer for more specific details.

Pre-lubrication of these screws before use is very important. It is recommended that a high zinc content assembly oil be used to prevent galling on the initial start up. Do not use anti seize of any kind on pushrod tips and adjusting screws. Anti seize contains soft metal particles that turn into an abrasive at a high temperature and doesn’t allow the engine oil to coat the friction points properly.

To go along with your adjusting screw, we offer poly lock jam nuts, featuring a light weight 12 point design. They are designed to mate perfectly with our diesel adjusting screws and the surface of the rocker arm body. For customers who purchase D-838 Duramax adjusting screws, we suggest pairing them with our D-852 jam nut with our D-828 & D-837 screws we suggest pairing them with our D-851 jam nut.

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