Comp Cams Trunion upgrade potential problem
12-12-2010, 12:00 PM
#1
Comp Cams Trunion upgrade potential problem During the week I installed the Comp Cams trunion upgrade on my factory LQ9 rocker arms. What I found was that 9 of the rocker trunion installs were great. They were silky smooth and easy to rotate. However, the other 7 were varying degrees of stiff and catchy.
When the first unit came out stiff, I assumed that perhaps I did not get the bearing in straight or there may have been a burr in the bore that I did not detect. However, after taking great care and still getting several more poor results I realized there was something else causing the problem.
What I found was that there was a problem with the factory rocker bearing bore. I knew that it was either deformed or undersized. The reason this was not a problem with the factory trunion setup is because they have much more bearing clearances than the Comp Cams set up. So, this increase in crush on the bearing race is not an issue. But, because I do not have a dial bore gauge that small in diameter, I had not way to know which was the problem or to verify the measurements with enough accuracy.
While not exactly the ideal scenario without the proper dial bore gauge to measure the progress, I decided to lightly hone the rocker's bearing bores and try it again. After the first try, the bearing was much looser and smoother, but still not right. So, I honed a little more until the bearings were free and smooth.
Once I realized this was the solution, I honed the remaining 6 rockers. Now I have a full set of upgraded rockers with glass smooth bearings.
I do find it hard to believe that I am the only one to experience this problem. The engine that I removed the rockers from is a low mile engine in excellent condition. Are other people just running them not realizing they are supposed to be silky smooth and free? But, I have not found a single other post on the net of people complaining about this problem.
Anyhoo, I just wanted to share my experience in case any others run into this problem.
When the first unit came out stiff, I assumed that perhaps I did not get the bearing in straight or there may have been a burr in the bore that I did not detect. However, after taking great care and still getting several more poor results I realized there was something else causing the problem.
What I found was that there was a problem with the factory rocker bearing bore. I knew that it was either deformed or undersized. The reason this was not a problem with the factory trunion setup is because they have much more bearing clearances than the Comp Cams set up. So, this increase in crush on the bearing race is not an issue. But, because I do not have a dial bore gauge that small in diameter, I had not way to know which was the problem or to verify the measurements with enough accuracy.
While not exactly the ideal scenario without the proper dial bore gauge to measure the progress, I decided to lightly hone the rocker's bearing bores and try it again. After the first try, the bearing was much looser and smoother, but still not right. So, I honed a little more until the bearings were free and smooth.
Once I realized this was the solution, I honed the remaining 6 rockers. Now I have a full set of upgraded rockers with glass smooth bearings.
I do find it hard to believe that I am the only one to experience this problem. The engine that I removed the rockers from is a low mile engine in excellent condition. Are other people just running them not realizing they are supposed to be silky smooth and free? But, I have not found a single other post on the net of people complaining about this problem.
Anyhoo, I just wanted to share my experience in case any others run into this problem.
12-12-2010, 12:07 PM
#2
Good info here. I noticed when installing mine if I made it too tight it would bind up and be stiff as you mentioned. So I backed the bearings out a little bit and wala. I know its not the same as your problem but still some info helpful for ls1 rockers if anyone is having problems. Oh also I used 2 16mm sockets and a hammer and each rocker took about 10 seconds to assemble lol. I saw a write up that used a vice but the cave man way worked 10000x better and faster.
12-12-2010, 01:57 PM
#3
11 Second Club
^this guy is right. i installed mine myself as well with a bench vice, some sockets and some fabbed up flat plate with holes in it. there is supposed to be a little side to side play when the rocker is on the shaft. not much but i used the stock rockers as a guide for how much slack i would leave. after doing that and putting some oil on them they road like glass and i have absolutely no valvetrain noise.
i would not have honed the rockers out...i think you set yourself up for problems down the road considering the forces that the valve spring puts on the rocker. you need the tight tolerances.
i would not have honed the rockers out...i think you set yourself up for problems down the road considering the forces that the valve spring puts on the rocker. you need the tight tolerances.
12-12-2010, 04:41 PM
#4
When it comes to bearing tolerance, it is not a case of tighter is better. There is simply proper tolerance or not proper tolerance. Too lose is bad and too tight is bad. In this case, it appears there was too little tolerance. The bearings were actually binding. Had I installed them the way they were, I am pretty sure they would have suffered bearing failure pretty quickly.
Last edited by speedtigger; 12-12-2010 at 05:33 PM. Reason: expanded on the reply
12-12-2010, 06:10 PM
#7
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Same here. I noticed mine were binding up If I pressed the bearing in too far. I loosened them up by pressing the bearing out a little. Some are smoother than others but it should be fine.
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12-12-2010, 09:07 PM
#9
s Oh yeah. I expected them to tighten up once pressed in. I would like to know what the specifications are on the interference fit. It does not say in the directions. I sent comp tech an email on this, we shall see what they say.
Did you notice how loose the factory bearings are?
Did you notice how loose the factory bearings are?
Last edited by speedtigger; 12-14-2010 at 09:57 AM. Reason: spelling
12-13-2010, 02:09 AM
#11
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Speedtigger, although I do not have the comp trunion upgrade and have never installed one I can say I agree with your installation. I have had the EXACT same thing happen several times with u joints. It is absolutely wrong to run a roller bearing/race that is under a constant bind. It will fail prematurely. Some may think you are setting yourself for problems, but I say you adverted one...or 6 rather. So 
03-06-2011, 10:46 PM
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I did mine the other day so I wanted to give an update to add my experience. They all slid in perfect, without issue. I noticed on a few that upon first rotation they were a little notchy, but very quickly they smoothed out and turned like butter. Makes you wonder if they changed something in the design and that would account for the period of time they were out of stock everywhere.
03-07-2011, 02:54 PM
#16
cool, whats the PN on the new bearings? I have a new set coming I'll check the specs, and have a set here thats 6months old the 5000675802 shafts are .06250 FYI. I dont have a .500+ pin gauge set to measure the ID of the bearings (5000601), there the KN-101305 UBI/made in the USA. But I'll see how they fit, test and installed, compared to the older set.
04-17-2011, 05:13 PM
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Any updates? I am in the process of 243 head/cam swap and doing the trunion upgrade as we speak. Im not so lucky either. I have 3 out of 16 that are just not right. I tried to back them out as stated above and they still feel like ****.
Anyone have any more info with a fix for this?
Anyone have any more info with a fix for this?
04-17-2011, 06:00 PM
#19
The terms "tolerance" and "clearance" are not interchangeable here on Earth.
04-17-2011, 07:53 PM
#20
"Too lose is bad and too tight is bad. In this case, it appears there was too little clearance."
That one word error does not seem to justify your evaluation of the post unless I am missing something.