FYREANT

NOTE: This How-To guide is neither endorsed by or property of Corvette Forum or myself in any way/shape/form. All liability stemming from any actions taken in relation to this guide is solely placed upon the end user. (This means you!)

Today we are going to cover how to upgrade your rocker bearing trunnion's for you cylinder heads. When you are doing a cam kit, more than likely you will be upgrading all kinds of goodies such as lifters, trays, adding a phaser limiter, etc. The trunnion upgrade is one of those things you surely don’t want to skip out on.

So, what are trunnion's and why should I upgrade them? Well, like the LS before it, the LT1 and LT4 rocker arms suffer from poorly designed bearings for the rocker arms. The bearings themselves are needle bearings and reside inside a bearing retainer that mates to the trunnion itself. If you happen to have a rocker arm break, then the cover will pop right off the side of the rollers, and needle bearings will go all throughout your motor! Oh no’s!! This is what these bearings looks like:



Enter the trunnion upgrade. Comp Cams has developed an upgrade kit so that the bearings for your rockers are protected from being lost in the engine by utilizing stronger alloy steel along with a retainer that “captures” the needle bearings so they can’t fall out.



Awesome! How do I put it in?! Let me show you.. 
First, you need to remove all the rockers from you cylinder heads. I would recommend getting a box like I did, mark which way the front of the motor is, poke holes in it for the existing rocker assembly bolts to go into as seen below.



Ok, now its time to start disassembling your factory rocker arms. To do this you will need either a press or a vice. (a drill press would even work for this). ONE AT A TIME, bring one rocker arm over to the vice, along with a 21MM socket, and a 9/16 socket. (sizes may vary depending on brand of socket). Let’s examine the rocker arm – You’ll notice that on one side of the rocker arm there is two flat spots as shown in the pic below with yellow arrows. We will use this side as our “receiving end”.



Here you will need to take the 21MM socket and put it on the receiving end of the rocker as shown below. Then, the 9/16 socket will go on the close side of the rocker, and will be used to push the trunnion and bearings through to the other side which will be caught by the bigger socket as you close the vice.





Once you get about half way through pushing it out, the trunnion will pop loose and the caps and needle bearings will want to go everywhere. 10 points if you keep them intact, and yes I am keeping score!



Now that you have gotten the trunnion and bearing out of the rocker arm. You’re ready to put the new stuff into it. Bring over the two black washers that they provided for you, they are critical to use! You will also want to bring over the new trunnions, and two bearings with you to the vice.

NOTE: THE BEARINGS DO HAVE AN INSIDE AND AN OUTSIDE! MAKE SURE THE SIDE OF THE BEARING WITH WRITING ON IT FACES OUTSIDE! Lets face it, if you screw this up, you simply have to press it out and do it again..



Put the trunnion into the middle of the rocker arm, and put one bearing on the receiver side of the rocker arm, remember, that’s the side with the two flat spots on it.



Next, we will need to use the vice to start pressing in the bearing. The washers are perfectly sized to allow the trunnion to come through the middle of the washer, and will push the bearing into the rocker around the trunnion. As you can see below:



Put it on the vice or press, whichever you prefer, and press the bearing in. You will want to keep going until the washer is flush with the side of the rocker arm and it “stops” when there is no more bearing to push in. Once this bearing is in, now we will need to do the other side. To do this, we will use both washers, and situate them like this:



Now use the vice to press the bearing in on this side. Again, In both cases, you will want to go until the washer stops against the rocker arm.



Once you have them both in, you’ll want to double check that the letters are facing out as we talked about earlier..



Next, we need to install the retainer clips. Grab two retainer clips, one for each side, and use your retainer clip pliers to install them.



These should seat on the trunnion completely in the grove that is present on them on both sides. Once these “snap rings” snap into place, one of the things I like to do to make sure they are in there correctly is to “spin them” a small amount to make sure they are not binding up anywhere.



Do this for both sides of the rocker arm, and then go put it back in the box you made to keep everything together. It’s important to make sure you keep the same rocker arms where they mounted before! Now you can take another one and start the process again. Only 15 more to go!

That’s pretty much it. Stay tuned for more How To guides coming your way. 

Ant

FYREANT

One thing I will mention is that the replacement rocker bolts that come with the Comp Cams trunnion upgrade kit, part number 13702-KIT, includes bolts that are too long and intended for an LS. Because of this short bolts are necessary for the LT1/LT4 heads. I don't have a part number for these as they were furnished for me by Vengeance Racing. Big shout out to them as they have been uber professional to work with for getting parts and questions answered.

robert miller

Looks like again a great post & you have it down. I think from BT racing this is the best way to go hands down on a rocker arm upgrade.

Ant, great job man as always. Robert

bigsapper

The mods just need to go ahead and make a sub forum called Fyreant's How-tos.

FYREANT

Lol I sure wouldn't be opposed to that haha

Got a handful more guides to write this weekend too. Stay tuned!

C5-VERT

Doing this right now with Smith Bros trunion upgrades! Thanks for the write up FYREANT! I have instructions and a service manual on USB but it sure helps seeing it done real world in pics. Good stuff.

FYREANT

Of course, anytime brother!

Corvette-Dan

Can't one just buy rocker arms that feature this enhancement?

FYREANT

No. Nobody makes them that I am aware of for the Gen V LT motor.

us3rname

I noticed the same with the BTR trunnion upgrade. Really wish they would have an option for the lt1/4 specific bolts vs sending them all out with LS bolts. Good write up!

Corvette-Dan

That seems crazy, which makes your post all the more important for those that need it.

Thank you.

C5-VERT

Right here: https://www.michiganmotorsports.com/...4-lv3-l83-l86/

Vengeance Racing recommended smith bros so went with those due to zero bearings to fail. They use bronze ones with oil galleys. But regardless the above link is what you want fully installed and with a core return.

I personally think it's easy to do so not worth the money to buy installed. But depends on your time, or if you're even comfortable with doing it.

C5-VERT

FRYEANT here are the ARP rocker arm bolts I upgraded to: ARP 8740 Pro Series GM LT1/LT4 Rocker Arm Studs 234-7208

Amazon link direct from ARP $50:

C5-VERT

One other tip I would highly recommend when taking the stock rocker arm bolts off, use HEX style sockets. Do not use the bi-hex or 12 point or other types. They won't fit as snug and prone to stripping the edges when getting them loose. I made the mistake of using one of my bi-hex impact sockets and it stripped the edges of the bolt. It comes off sure, but not without damaging the bolt head a bit. Hex sockets fit perfectly being a HEX bolt so use them! :-)

FYREANT

Thanks for providing the info! These bolts are not actually the same as what I have in mine. Mine are not studs, mine are allen style bolts.

C5-VERT

Welcome and gotcha. Yeah never really heard of any real need for rocker studs, at least for 95% of builds on these GenV LTx's. Funny thing is I snagged those ARP studs b/c they priced them at $48! I see now they are listed double!! Yikes!

emperors61

Any updates on how these are holding up in installation?

FYREANT

until I disassembled and sold parts of the engine, they held up great. I still have them and will install them in my future C7 Z06