Volume I, Issue 4, Page 40

Rock On!

I think all Mopar racers will agree that rocker arms are a problem on a big block engine once you get it in race trim. I have built and raced big block Mopars since 1979. Some were Super Stock legal but most have been for bracket racing. We put together everything from 383” engines to the 572” engine in one of our current dragsters. We have broken just about every valvetrain component on a Mopar, but in my opinion the rocker arms stick out as the weakest link.

I’ve had a lot of conversations with other racers and manufacturers over the last decade or so to come up with what I feel are two solid options for us big block Mopar owners. Durability was probably my first goal, but they needed to work in conjunction with the

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camshaft we had chosen for the engine.

There are two main things to consider in choosing the right rocker arm for your particular engine. The first thing you need to decide on is what the specifics of your camshaft are or will be if you are in the planning stages of building a new engine. The decisions you make now can save you a lot of money and prevent a lot of frustration later.

BOLT-ON REPLACEMENT ROCKER ARM OPTION:

The first example I will use in making a rocker arm decision will be rocker arms that bolt onto the rocker shaft pedestals on stock type heads. This was the type of rocker arm we needed for our 500” low-deck engine that we have a set of Mopar Performance Stage VI heads on. We chose a Comp Cams roller cam with .655” lift and a pretty “soft profile” that would be easy on valvetrain parts in general. We talked to a couple different companies on their recommendations and we settled on Comp Cams Pro-Magnum rockers, part number 1321-16. They are known for durability and quality and come with hardened shafts and all the spacers and mounting hardware.

We received the rocker arms and did a pretty straight forward install.


This broken rocker arm is what sent me on the search for an economical rocker arm that would last more than one season. You can see the break on the bottom of the rocker arm.

The Stage VI Mopar heads on this engine uses all OEM style valve gear. The rocker arm shaft pedestals, mounting bolts and oiling system are all stock design.

Note: Inspect the parts and wash with solvent. When putting the rocker arms on the shaft I recommend coating it with ARP moly assembly lube for protection during initial startup and during the valve adjustment procedure. We checked to make sure there was clearance between the rocker arms and the valve springs and retainers. Ours had over .060”. If yours are rubbing or are closer than .025” I suggest relieving the rocker arm with a die grinder to get that clearance to .050”-.060”.

Next up was making sure we ordered the correct length pushrods. To get the correct length we ordered a couple “test pushrods” from Comp Cams. They are inexpensive and are threaded so they can easily be adjusted about 1 inch in length. I set it for the length of pushrod I removed so it would be close. The old ones were definitely not going to work as the Comp Cams Pro-Magnums require ball-type ends and the ductile iron rockers I was removing used the cup-style on the top of the pushrod.

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