You Cam Do It! Replacing Cam Bearings at Home

Posted on March 23, 2015 by Jefferson Bryant in Engine, Tech // 0 Comments

For some reason, cam bearings hold an air of mystery and voodoo mechanics for many at-home builders. Professional engine builders often leave the cam bearing installation to the machine shop, and while some of that may be for the sake of time management, the fact that they don’t even own the tool to do it is mind-boggling. I know this because when it came time to change out the cam bearings in a Mopar 383, I asked all my buddies if they had a cam bearing tool I could borrow—to no avail. Not a single one had ever changed their own, and a few of these guys build high-dollar motors for other people. I ordered a cam bearing installation tool from Comp Cams (PN 5312) and got to work. There are several key points to working with cam bearings. First, take your time and be careful, you can damage them if you drop or nick the edges. Second, pay attention to the old bearings and match each one to the new bearings. They are different from #1 to #3 and so on. Finally, you must clock each bearing to align with the oiling holes in the block. Failure to do so will result in a catastrophe. Each bearing should be installed dry, without any lubricant or oil on the block or the outside of the bearing. Replacing the cam bearings is not incredibly difficult as long as you follow the rules and pay attention. If you plan on building only one engine ever, then having the machine shop do the work versus buying the tool may be worth it. For me, the satisfaction of doing it on my own is worth the effort.

01. In order to remove and install cam bearings, you must have an install tool. You will be much better off purchasing a quality universal tool as opposed to a cheap bargain tool store unit. We got ours from Comp Cams. Note the box of bearings; we have them numbered 1-5 in order of placement in the block.

02. The install tool uses an expanding spindle that slides into interchangeable drums. Each drum is designed for a specific range of inner diameters for the cam bearings. The drums are made of a heavy band surrounding 4 steel sections.

03. The drum slips over the spindle and locks into place. The spindle has 4 expanding sections, just like the drum. These need to line up with the sections of the drum; otherwise, it won’t expand correctly.

04. The stalk of the install tool compresses the expansion spindle, which expands the bearing drum. The band grips the cam bearing, allowing you to drive it in or out.

05. Before threading the spindle to the stalk, the plastic guide cone must be in position. The cone centers the tool in the block using the cam bearing holes.

06. With the block on an engine stand and flipped upside down, I slid the bearing tool through cam bore. There is no specified order, but I start at the rear of the block, knock out the freeze plug, and then the bearing.

07. The large nut on the end of spindle is a hex nut, with the drum inside the bearing, you need to turn the nut with a wrench (I use a ratcheting wrench from Gearwrench, it is much easier) until it is tight so that the drum does not push out of the bearing.

08. Once tightened, a hammer is used to knock the bearing out of the block. You want to remove all of the bearings before moving on, unless you are only replacing one. If you are at this point, there is no real reason not to replace them all. Now is the best time to thoroughly clean the block.

09. To install the bearings, the tool is once again placed in the cam bore. The bearing is placed on the drum after the tool is in position. You can’t do this outside the block.

10. Here is the Gearwrench in use. There is not very much room to work with inside the block, so a ratcheting wrench makes this so much easier than an open-end wrench. The hardest part of this job is keeping the shaft from spinning while tightening the spindle. A small pipe wrench or slip-joint pliers works great.

11. Then the bearing gets set into position with the correct clocking.

12. Then the bearing is knocked in place with a sledge hammer. A 3lb hammer is just about right. You want to keep one hand on the plastic centering guide, if the bearing gets cocked to the side, it will get ruined.

13. Using a flashlight shining into the cam bearing, you can see the alignment of the bearing to the main oiling hole. You need to check this on every bearing.

14. Some bearings have one hole while others have two or three. You can see that this Mopar bearing has the main feed hole on the bottom and two smaller holes up top. These feed the lifter galley, and they are not interchangeable, you have to line them up right. There are specialty bearings available with grooves on the backside, the grooves allow more oil to circulate around the bearing and out to the block.

15. Getting the bearings perfectly lined up is not easy; you need to take your time. Here, the oiling hole to the right is just off center. This is acceptable; you should have seen the factory bearings, a couple of them were way off.

16. One trick for keeping the holes lined up is marking the bearing and tool for alignment. Sometimes, the bearings try to rotate in the bore, making it difficult to install the bearing correctly. This will show that and help you correct it.

17. The block was marked for the main oiling hole; this corresponds with the cam bearing marks on the tool.

18. Once the bearing is driven in place, you can see if the hole is lined up or not. There is an acceptable range for being off, maybe a 1/16 of the hole. Another option is to chamfer the oiling holes in the block with a carbide bit. This eliminates the overhang of the block-to-bearing hole issue, and it will actually increase oiling to the camshaft and subsequent system down the path. Just make sure you clean the block out before installing the bearings.

19. Once all of the bearings are installed, the rear freeze plug needs to be installed. You also want to check the fit of the camshaft. If there is any binding at all, you have a problem. Find the bad bearing and replace it before doing anything else.