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I recently bought my '03 Z06 and have to tell the story first, to explain what the pictures will show! The PO had a spring fail fairly recently and got lucky with no damage other than the spring itself. He took it to the dealer who replaced just the one broken spring. The bill was not cheap and no doubt this was a factor in the car being put up for sale before more damage and bigger repair bills. I bought the car knowing this and expected to change the springs, so I posted last week to get my shopping list together:
I used the TDC method, but found out right away that bringing each cylinder to TDC was the hardest part of the job. A breaker bar doesn't fit on the balancer bolt because the steering rack is in the way. I had to use a 24mm offset box-end wrench. It is not easy to turn over and I'm working on this by myself.
Anyway, one cylinder at a time. I got the tool from ebay and it worker very well. In hindsight I could have bought the Summit tool to do two valves at once and saved an hour. It's fine, I enjoyed the work.
Getting TDC for each cylinder was a lot tougher on the driver's side but I got it. Now that I've done the job I would use air and not the TDC method if I did it again.
It took the better part of the day and I'm sore since I don't do this kind of work a lot. It was a fun project and everything went 100% fine as planned. With the new plugs and wires I believe it's running a little better too! Worries are gone and now we can spin this engine up a little!
I researched the rocker trunnion bushing options, and it looks to me that they are used to add dependability for high RPM use. Mine is just a daily driver and will spend 95% of it's time under 3,000 RPMs.
One good thing though is that you can get to those rockers very easily. 10 minutes per side and you could have them back out.
Are there benefits for a street-driven car? Or do they go in the "overkill can't hurt" category?
Originally Posted by GUSTO14
Congratulations on a job well done!!!
Just one question, did you do the upgrade to the rocker arm trunion bearings while you had them apart?
Ha! Yes, that helps! I did that, but it was still pretty darn stiff to turn over. I think I could have pulled both rocker covers and removed all the rockers instead of one cylinder at a time. Then I would just have the friction from the rings and not all the valve springs. That's a good lesson learned.
Originally Posted by neutron82
next time pull the plugs and the motor will turn over much easier
I researched the rocker trunnion bushing options, and it looks to me that they are used to add dependability for high RPM use. Mine is just a daily driver and will spend 95% of it's time under 3,000 RPMs.
One good thing though is that you can get to those rockers very easily. 10 minutes per side and you could have them back out.
Are there benefits for a street-driven car? Or do they go in the "overkill can't hurt" category?
Actually I think they would fall into the preventive maintenance/dependability category. The factory trunion bearings have a bit of history of failing, not unlike that of the original springs. Albeit no doubt on vehicles that see higher RPM from time to time. If one does fail however, the results can be expensive. I think all else being equal if I removed the rocker arms for any other reason, I'd change out the trunion bearings as well.
At this point, I wouldn't loose a lot of sleep over it, but I would add it to a long term list of things 'to-do' the next time I was in there.
Thanks Gusto. I watched the video you attached and those are the needle bearing style that he installs. I think I like the idea of the bronze bushing style upgrade. Do you have experience with these? Which is preferred for long-term reliability in a street application?
Originally Posted by GUSTO14
Actually I think they would fall into the preventive maintenance/dependability category. The factory trunion bearings have a bit of history of failing, not unlike that of the original springs. Albeit no doubt on vehicles that see higher RPM from time to time. If one does fail however, the results can be expensive. I think all else being equal if I removed the rocker arms for any other reason, I'd change out the trunion bearings as well.
At this point, I wouldn't loose a lot of sleep over it, but I would add it to a long term list of things 'to-do' the next time I was in there.
Thanks Gusto. I watched the video you attached and those are the needle bearing style that he installs. I think I like the idea of the bronze bushing style upgrade. Do you have experience with these? Which is preferred for long-term reliability in a street application?
No, sorry I don't. But all else being equal, I think I'd go with the needle bearing replacements. The LS bearings don't fail from fatigue, they fail because the needle bearings come apart. Apparently not a great design.
I've run Crane needle bearing rocker arms on a number of SBC's and SBF's on street and race cars and never had a failure. I've also not heard anyone complain that the LS replacement bearings are a problem, just on the factory bearings.
Stay away from the needle bearing trunnion "upgrades". I haven't heard anything bad about the bronze bushings yet, but after getting burned once, I switched back to OEM and I am happy.
If you search for a post by Eric D (GM Employee), the LS1/6 rockers were upgraded to eliminate the bearing issue. Don't recall the exact year they were changed but I think the 03 may already have them.
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Slideshow: A Jaguar designer's personal project imagines what a modern front-engined Corvette might look like if Chevrolet revisited the golden age of the Stingray.
Yellow Valve Springs - Done
