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I know Durabond is the popular brand for cam bearings. I have used them myself on the last engine I built. I tried using them again on my current build. Unfortunately, I keep getting bad bearings. The CH-25 kit comes with 2ea CH-25-1, 2ea CH-25-2, and 1ea CH-25-3 bearings. The CH-25-1 bearings are good. They have about .002" clearance. It's the CH-25-2 and -3 bearings that are too small. The -2 bearing has about .0002" of clearance, so basically the same size as the cam. The -3 bearing has about -.0014" clearance. So, the center bearing is smaller than the cam. I plan on calling Durabond tomorrow. Hopefully, they will fix this issue before all LS builds are put on hold. Hopefully, other people are checking their cam bearing clearances. I doubt I got the only 2 sets of bad bearings.
Is there another reliable brand of cam bearing that people are using?
I called and talked to someone at Durabond today. Of course, almost everyone was still on vacation, so nothing will actually happen until at least Monday. The person I talked to said that they have not heard of anyone else having this problem, but they would send me a new set of bearings anyway. I asked them to measure the bearings first, because I don't need more bad bearings taking up space. Hopefully, the right people will be back at work on Monday to figure out what happened to these bearings. Stay tuned....
Are you trying to use the 25’s in your 2000 block? You need the 10’s if your working on the car in your sig. The 25’s are for a 2004+ block. The guys at DuraBond already told you this I’m sure however, so I’m guessing that your working on a later block.
No, I'm not rebuilding the LS1 at this time. I know it takes a different part number. I'm currently building an LS3-ish stroker. I think it's a 2008-2009 L92 block. The bearing fit into the block with no problem. It's the cam that won't go into the bearings. The inside diameter of the bearings is too small for the cam. Everyone uses the CH-25 bearing kit. I'm surprised that I'm the only one having this issue. At least, Summit, TSP, and Durabond make it sound like I'm the only one. So far, everyone I have talked to about this has never heard of anyone having this problem. I know it's not user error, because I actually measured the bearing inside diameter. I just hope Durabond fixes the problem soon.
It's a TSP custom grind. They said the journals are supposed to be 2.165". I measured all the journals, and they are 2.165".
Durabond called me yesterday. Their engineer measured a set that they are going to send me. I'll double check them before installing them in the engine. Hopefully, this set will work.
UPDATE: the 3rd set of bearings did not help at all. I still can't get the cam into the block. The cam will get stuck before I can get it all the way into the block. I called my local machine shop, and found out that this is a common/known issue with 6.2L blocks. He said it only happens with aluminum blocks. This is my first build with an aluminum block, which is why I never had this issue before.
Basically, the cam bearings have to be machined to match the cam journals. There's nothing wrong with the cam, bearings, or the block. They just don't all fit together. Bottom line is, the block is going back to the machine shop.
UPDATE: the 3rd set of bearings did not help at all. I still can't get the cam into the block. The cam will get stuck before I can get it all the way into the block. I called my local machine shop, and found out that this is a common/known issue with 6.2L blocks. He said it only happens with aluminum blocks. This is my first build with an aluminum block, which is why I never had this issue before.
Basically, the cam bearings have to be machined to match the cam journals. There's nothing wrong with the cam, bearings, or the block. They just don't all fit together. Bottom line is, the block is going back to the machine shop.
Quote: I called my local machine shop, and found out that this is a common/known issue with 6.2L blocks. He said it only happens with aluminum blocks.
My LS3 block (6.2L aluminum) had zero issues getting cam in the block.....no bearing machining etc..
@Che70velle It sounds like something has shifted/warped slightly, and the bearing diameters are not in alignment. Might only be .001"-.002", but that may be enough. I have never heard of guys grinding down the cam journals to custom fit a suspect block. I may be wrong, but I've never heard of it personally....
@Che70velle It sounds like something has shifted/warped slightly, and the bearing diameters are not in alignment. Might only be .001"-.002", but that may be enough. I have never heard of guys grinding down the cam journals to custom fit a suspect block. I may be wrong, but I've never heard of it personally....
Ive seen shops hone the cam bearings to get the correct cam fitment, on both iron and aluminum blocks. @KCS can vouch for this as well as I’ve read posts where he’s talked about it.
In my opinion there is other problems here. The 6.2 block comment is false. I’ve built plenty of 6.2’s and never had a cam fitment issue. Something else is going on here
I have seen this quite a few times on the aluminum LS blocks. It can be a total PITA to deal with during a rebuild - but it is not uncommon. The cam tunnel may not be straight end to end. This is why you see the cam bearings on some blocks showing the copper overlay. I remember getting brand NEW GM blocks that showed this. The bearings are installed in the block and then broached. The reason for the misalignment in the blocks is because they are bored from each end of the cam tunnel independently, to 'meet in the middle' during manufacturing. A good machine shop will have a smaller mandrel for their align hone to true the tunnel - it doesn't take much. Oversize O.D. (outside diameter) shell bearings are available.
Yeah, Durabond sent me new bearings, but they still don't fit. I think the bearings are fine. I think it's just a "bad" block. It seems like a common issue with aluminum blocks, especially the 6.2L. My machine shop deals with this often enough to have a tool made specially for this. I'm not real sure if they actually cut the bearings, or if they cut the cam tunnel. Either way, they seem to know how to fix it. The guy said they do this "all the time". I'm sure that's an exaggeration, but it's often enough that he knew what was going on before I finished describing my problem.
I'll report back once I get the engine back. I have to evict a squirrel from my truck first. It seems to think my air box is a nice home. I'm not sure if the squirrel caused my sudden loss of coolant or not, but I need to make sure everything is ok with my Duramax before I continue building the 418. I can't afford to burn up a pre-DEF diesel.
On my LS3 I had the opposite result where the clevite cam bearings were too loose and the durabond worked well. Issue was with low hot oil pressure with the clevite bearings. Not sure what the machine shop did besides change out the cam bearings to address the issue but they did first try a different oil pump (COPO spring), pickup tube O ring and LS7 lifters in place of the johnson 2110r's.
Hot oil pressure is good now and the machine shop worked with the repair shop to cover most of the costs troubleshooting the issue. The machine shop did mention one instance where a customer picked up a block and couldn't get their new cam to go in while the machine shops "house cam" that they use to check with slid in fine.
It is absolutely a block issue. Durabond makes good bearing shells/inserts. The fact that 2 sets won't work tells me it's the block, NOT the inserts/shells.
I finally found time to get the block back to the machine shop. They fixed the issue and installed the cam bearings for me. Now, the cam slides right in and spins like it should. This budget 418 build is back underway. Here's a few pics:
cam installed new cam retaining plate new 4" crank installed forged pistons and H-beam rods going together bottom end almost done checking deck height
Yes. They had to cut and buff the bearings. It's likely core shift in the block, but it wasn't a lot. The bearings just needed a little more clearance on the inside.
Urinator, best case scenario is you found TDC with that magnetic base mic setup, but you can’t find deck height with that tool. You need a deck bridge to be accurate, in finding deck height.
Urinator, best case scenario is you found TDC with that magnetic base mic setup, but you can’t find deck height with that tool. You need a deck bridge to be accurate, in finding deck height.
yes, you are correct. I was getting TDC with the magnetic dial gauge. I don’t have a bridge, so I use a metal ruler and feeler gauge to check the gap. Turns out, theses pistons are right at zero deck.
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Cam bearing recommendation 
