Whether you’re building a 4.8L, 5.3L, or 6.0L LS wrecking yard engine or just looking to freshen up the top end of your LS, Its very important to upgrade the trunions. With the age of the LS based engine, it is not unusual for them to have 150K-250K miles on them. With mileage like that you can imagine how many cycles the rockers must have on them. Brought to you by Comp Cams, Richard Holdener with Speed Secrets explains the DIY Trunion upgrade kit from Comp Cams.
Disassembly is fairly straight forward. First you remove the plug wires, coil packs and valve covers to access the rocker arms. You can use an impact to remove the coil packs and valve cover bolts, but you will not want to go at the rocker arm bolts with an impact until you have first backed them off by hand. With the rockers unbolted remove them all at once by pulling up on the seat so that you can take them to a work bench and still keep them in order.
With the rockers sitting on your bench, its time to unbox the trunion upgrade kit from Comp Cams. Inside you’ll find everything you need to complete the upgrade, including a magnetic die and a mandrel for removing and installing the trunions. Install the first rocker on the magnetic die, Center the mandrel on the stock bearing and trunion, and install the assembly into a vice or press. Press out the stock bearing being sure to catch the rocker with your hand and remove the stock trunion and bearing. With the stock and Comp trunion and bearings side by side there really is no comparison between the two. The Comp trunion features a solid shaft for the high quality needle bearings to ride on, while the stock trunion is wedge shaped, sacrificing some strength for the sake of accommodating a Semi-sealed bearing and race.
Now that you have a stock, bare rocker casting, place one of the new bearings on the rocker arm with the writing on the side of the bearing facing out, away from the rocker, and position the mandrel on the bearing. Using the magnetic die on the other side of the rocker, install the assembly into the vice and press the bearing into place until the bearing face with the writing on it is no deeper than flush with the outside of the rocker arm. Install the rocker onto the magnetic die with the installed bearing facing the tool. Insert the new trunion, slide the other new bearing in place with the writing facing out, position the mandrel, and press the bearing in place. Using snap ring pliers, install the 2 snap rings and ensure that the rocker pivots freely. Replace the stock rocker bolt with the one from the kit and repeat this procedure for the rest of the rockers. When the trunion upgrade is complete your rockers will be ready for a higher spring rate, more mileage, and more fun.