LS cam bearings

[machinedave]

I have been having trouble with LS cam bearings in some Aluminum blocks. It seems to be #3 that is causing the most hassle. I use Durabond CH-10 for the small housing bore older blocks and durabond CH-25 for large housing bore newer blocks. They feel just fine going into the housing bore but the cam will not go in. Anybody have any ideas?

[BillK]

Dave,
I havent had a problem except for the last two I did. I just did two for the local Chevy dealer. They were the 427 Vette blocks with a strange rear bearing with a half moon cutout in the bearing. They all were fine except for the back one. I had to do a little scraping on it.

One thing I have noticed for sure is that the oem bearings, which are a split type like Clevite, seem to leave a scar in the cam bore right where the bearing split is. I take a sanding roll and make sure to get rid of that "scar" If you dont get rid of the scar it can distort the bearing for sure.

Also..... seems like the aftermarket cams are a little bigger than the oem ones. I always tell my customers to bring me their cam to try. I have a stock one that I use but have had one come back for some fitting after they tried their aftermarket cam.

And .... if you are not aware of it the bearings have all been upgraded to the wider ones. I forget the Durabond number right off hand.

[CGT]

I had problems finding a thin enough rubber sleeve for my tool for LS's. It tended to wanna roll the leading edge of the bearing up a bit. Which the aftermarket cam bearings are more susceptible to because the have much more chamfer in them than the OE bearings.

[BillK]

I had problems finding a thin enough rubber sleeve for my tool for LS's. It tended to wanna roll the leading edge of the bearing up a bit. Which the aftermarket cam bearings are more susceptible to because the have much more chamfer in them than the OE bearings.

Glad you mentioned that. I think if you look at the blocks themselves they only have a slight chamfer on one end of the bore. I am pretty sure I have been putting some of the bearings in from the back side because of this. I have the old style K-Line tool with the rubber orings and it fits fine.

[machinedave]

Dave,
I havent had a problem except for the last two I did. I just did two for the local Chevy dealer. They were the 427 Vette blocks with a strange rear bearing with a half moon cutout in the bearing. They all were fine except for the back one. I had to do a little scraping on it.

One thing I have noticed for sure is that the oem bearings, which are a split type like Clevite, seem to leave a scar in the cam bore right where the bearing split is. I take a sanding roll and make sure to get rid of that "scar" If you dont get rid of the scar it can distort the bearing for sure.

Also..... seems like the aftermarket cams are a little bigger than the oem ones. I always tell my customers to bring me their cam to try. I have a stock one that I use but have had one come back for some fitting after they tried their aftermarket cam.

And .... if you are not aware of it the bearings have all been upgraded to the wider ones. I forget the Durabond number right off hand.

Thanks. I do clean up the scar with a half round file. I'm going to pull them out and measure the housing bores. The original part number was a CH-23 and the one i always use is the updated wider one is CH-25. Just to solve my curiosity I'm going to pick up a CH-23 and measure them and compare to the CH-25.

[machinedave]

I had problems finding a thin enough rubber sleeve for my tool for LS's. It tended to wanna roll the leading edge of the bearing up a bit. Which the aftermarket cam bearings are more susceptible to because the have much more chamfer in them than the OE bearings.

Thanks. I'm using a Durabond camshaft installer tool. With only the #3 bearing installed, I tried installing the cam from the non hammered side and still wouldn't fit. I have several used test fit cams that normaly fit fine that also wont enter.

[CGT]

I had problems finding a thin enough rubber sleeve for my tool for LS's. It tended to wanna roll the leading edge of the bearing up a bit. Which the aftermarket cam bearings are more susceptible to because the have much more chamfer in them than the OE bearings.

Thanks. I'm using a Durabond camshaft installer tool. With only the #3 bearing installed, I tried installing the cam from the non hammered side and still wouldn't fit. I have several used test fit cams that normaly fit fine that also wont enter.

Sounds like your going to have to get ugly with it. I've had to on a couple. Just make sure no one is looking

One thing I have noticed for sure is that the oem bearings, which are a split type like Clevite, seem to leave a scar in the cam bore right where the bearing split is. I take a sanding roll and make sure to get rid of that "scar" If you dont get rid of the scar it can distort the bearing for sure.

Yeah, I've noticed that as well.

[tjz450]

I had trouble also, with the wide bearings, cam wouldn't go in. Switched to the narrow set and the cam slid right in. Gen 4 block, both cam sets were durabond. The wider bearings seem to need a perfect alinement installation done. The cam tool mandrels that hammer-in, may not be good enough.

[A_VAS]

I've been 'relieving them' often to get cam in. the CH23P or 25P series seem hard enough that a Brush Research ball hone will clean them up without smudging. I find this easier than scraping

[machinedave]

So I removed the CH-25 wide bearings, reinspected and measured the housing bores. #1 is 2.3470" #2 is 2.3271", #3 is 2.3066", #4 is 2.3272" and #5 is 2.3470". I was happy with the housing bore measurements so this time I installed the narrow CH-23 bearings. The cam fits perfectly now. I wish I would have thought about measuring the bearing ID while it was still in the block. I do have another aluminum block here with exactly the same issue so I will measure the ID before I remove it from the block.

[modok]

Measure housing bore, check bearing thickness, should be all you need to compare.
I compare the thickness of the old bearing to the new bearing quite often.

Expanding drivers definitely not as good.
Use a solid driver if possible. Guide OD same as cam, driving step .030 smaller than housing.

[CGT]

Just had an ugly fight with cam bearings on my LS3 project. But I won! Sometimes it goes well with these LS's, sometimes it don't.

[Turbo231]

I have been told by a couple of people that the LS cam bearings from the factory are align honed to size after insertion because of shift in the aluminum blocks. This is why you can get some replacement bearings to work and some not. It depends on how much bore shift your particular block has. Can anyone confirm this and do machine shops that realize this also hone them to fit?

[CGT]

I have been told by a couple of people that the LS cam bearings from the factory are align honed to size after insertion because of shift in the aluminum blocks. This is why you can get some replacement bearings to work and some not. It depends on how much bore shift your particular block has. Can anyone confirm this and do machine shops that realize this also hone them to fit?

I believe this to be true. Not uncommon at all to see new or barely run ls's with gold showing through on random spots on random bearings, like they had been honed with bearings in.

[Turbo231]

I have also been told by others that unless the factory cam bearings have obviously been damaged, to just leave them alone. Some people will assume they are damaged when they see the align hone marks from the factory.