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To Trunion or NOT to Trunion (2009 Z06 in Trans Am)
I'm putting back together a Darton Sleeved engine and my mechanic recommended this Comp Cams Trunion Upgrade while it's going back together. Even though I see a lot of rave reviews and the theory behind the design sounds good, I also have a read a lot of horror stories.
The Good:
The stock rocker arm bearings on the LS1 have uncaged needle bearings which means that they can and often do come out of the races. (etc. Etc)
This kit upgrades those bearings so that the trunion bearings are steel roller bearings and most importantly caged and they will not come apart such as can happen with the stock rocker arm bearings. Smoother idle. More reliable in upper RPM range
The Bad and Ugly:
Damaged Snap rings that go thorough your engine
Trunion wear from improper lubrication. For some reason the bearings tend to start galling and eroding the trunion surface. Those posting with this problem have discovered the abnormal wear upon rocker disassembly.
Other "opinions":
I agree the stock rockers are still the best. Searching other forums it seems this "upgrade" fails more than stock rockers
I'm a fan of the stock rockers. They come with the car and they work. I very seldom see broken rockers on here but I've seen many problems when people change them.
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I don't know if the handful of problems I've read about are truly rare aberrations or could be due to bad installations, other oiling problems .. whatever.
I could use some more discussion and recommendations if possible. Do any vendors have mass experience with the Upgrade that can comment as well?
Guys on Corvetteforum have been dealing with valve issues on the LS7s since 2006. CHE is about the only rocker solution for the LS7 rockers that does away with those issues.
I don't know how the Straub trunions compare except that they are bronze bushed, but the CHE rockers are done in house and are bronze bushed too. Straub's are cheaper and look an awful lot like Comp's with different materials used. And can be installed with a simple press.
So I think either would probably work. The oiling is the main issue.
I had my valvetrain off and looked at my Comp/Lunati trunions and they were okay. So I'm going to run them a while longer. But you can see where the trunions themselves are soft and don't get proper oiling and can gall. So the bronze bushing takes load better (same reason bushed solid roller lifters hold up better vs needle bearings - more surface area). And the oiling seems to be improved with the Straub/CHE stuff as well which provides adequate oiling to the bronze bushing riding on the trunion.
We have now sold over 7000 kits for the year. We have several customers that have retro fitted the LS7 rockers with our kits. Some have reported the housing bore of the LS7 Rocker a little tighter, .0005 to .0007".
The overwhelming response after a retro fit is how quite the valve train is after installation.
Thanks for all the responses.
Jake, I appreciate the detail in your explanation. Nine8ss sounds like he has a firm opinion. ;-)
CStraub, So, I'm understanding if I get your Straub Kit, there would be a clearancing issue?
You said:
I'm not sure if you are saying the extra tightness is acceptable, or that some work needs to be done.
Can you clarify?
Thanks!
We have had 3 reports the assembly was tight. For the LS7's we have sold 27 kits. You can mic the housing bore before you assemble. You want a minimum of .0015" of press to max of .003".
While we do still offer our in-house rocker trunnion conversions, we also offer a kit that can be installed by the end-user with no need to press in any of the parts. After you remove the old trunnions and bearings all you need for assembly is snap-ring pliers! Price is $260 for the kit.
Just put my order in from tick for the straub kit! After doing alot of research, i decided to go with them. Have not heard one single issue with the straub kits. As far as i know, its the comp version that has had alot of failures
While we do still offer our in-house rocker trunnion conversions, we also offer a kit that can be installed by the end-user with no need to press in any of the parts. After you remove the old trunnions and bearings all you need for assembly is snap-ring pliers! Price is $260 for the kit.
It's about time... I called a few years ago and was told that "we don't sell kits" by some snide guy on the phone and my reply was that "some people don't want to make a lot of money".
Hi Jontall, i'm sorry you received less than desirable customer service when you called to inquire about our trunnion upgrades. This is a project that myself and the owner of the company decided to tackle at the request of our distributors and customers and has been in the works for some time now. Since this is my project, I apologize on behalf of CHE and would be happy to personally answer any questions you may have about our product.
Matt this is excellent. Can you provide any more details? It looks like there is a lip which catches the rocker body, so it's not a tight fit requiring a press. Are these the same ones you installed in house or different for the DIY'er?
Are their oiling channels on the trunnion body to force oil to the copper bushings?
Matt this is excellent. Can you provide any more details? It looks like there is a lip which catches the rocker body, so it's not a tight fit requiring a press. Are these the same ones you installed in house or different for the DIY'er?
Are their oiling channels on the trunnion body to force oil to the copper bushings?
Thanks for the additional information, guys.
Though I'm tapped out until after Christmas, I don't see completing the build on this engine without one of these kits.
The Comp Cams kit was just scaring me with all the negative commentary I'd seen. But, the principle seemed sound.
12-01-2016, 10:20 AM
To Trunion or NOT to Trunion (2009 Z06 in Trans Am) 
