Destroyed Cam Bearings!

[6TIME]

The way those cam bearings are being squeezed out at the bottom like toothpaste suggests to me that there are excessively high vertical forces acting upon them from above. The one common factor in all of these cam bearing failures is the aftermarket valve springs so it would be interesting to see if these failures can be prevented by using the softer stock springs.

When I had my first experience with cam bearing wear in the 4.0 I was running 110lbs seat and over 300 open with comp 926 springs. The last pic I posted was the #1 cam bearing in the 4.0 at 76k on the clock. It seems that Cam Makers don't always recommend the best spring for a given application...especially if it an engine other than a popular V-8. I began to realize that Comp had me running too much spring for the cam and rpm range of this motor. So in my new stroker build, i chose LS springs because they are beehive style and they have lightweight valves and very small retainers. Reducing the weight at the valve would allow me to run less spring. The stroker was setup at 75-80lbs seat and 240-245lbs open. This spring setup has only slightly more than stock spring pressures and the cam bearings failed at 26k....

[SilverXJ]

I'm not thinking cam walk is the issue either. It'd have to move pretty far to lose the oil film wedge. The only two things that the 4.0 and my stroker had in common was an aftermarket cam and different springs.

The cam can move 1/8" with the stock pin and spring setup. Thats with easy finger pressure. Now imaging it doing that several times a minute.

I very much doubt it. All the stock 4.0 engines made from '87-'98 had the thrust pin/spring to prevent cam walk and they didn't have any cam issues, so I think we can safely rule out cam walk as the cause of the cam bearing failures.

Thats with a stock cam. You throw an after market cam in to the equation and things change. More lift, more duration, more spring pressure. Not to mention how much tapper is ground into each different cam. Besides the tapper keeping lifter rotating it also helps keep the cam in the block. Also,early 4.2L engines did not have the the spring pine and they did experience cam walk via a slapping noise coming from the block. While I don't know what or if they had cam bearing issues associated with the cam walk with the stock cam.

I don't think so. All else being equal, the HV pump will raise the oil pressure by 25% compared to the stock pump so if you're getting 20psi hot idle with a stock pump, you can expect 25psi with the HV version.
My stroker's hot oil pressures are 25psi idle and 50psi above 2000rpm with 10W-40 oil.

Thats yours. Mine has been around 40psi @ hot idle w/10w30. Maybe your bearing clearances are larger than mine, IDK, but that is the experience of me and others with a HV oil pump.

The way those cam bearings are being squeezed out at the bottom like toothpaste suggests to me that there are excessively high vertical forces acting upon them from above. The one common factor in all of these cam bearing failures is the aftermarket valve springs so it would be interesting to see if these failures can be prevented by using the softer stock springs.

Softer springs will only work with certain cams. In my case the springs I used are the Mopar Performance. The spring seat has been machined for a taller install height. Seat pressure is 100 lbs and open is 225 lbs. Those pressures are nothing for a babbitt metal cam bearing.

However, another possibility is a binding issue. Check that the rocker arm is not binding on the rocker's trunnion. One way to check that is to use a piece of solder wire and rotate the engine a revolution or two. Check that the rocker ram isn't falling off the valve spring and binding on the valve retainer. Check that the push rods aren't binding on the head or any place else. Check that the lifters are free in their bores as well as seeing that the lifters rotate (push rod will spin). Check that the springs don't bind under maximum valve lift. Check that oil holes in the bearings line up with the oil passages in the block. Also, make sure your oil pump doesn't have an issue on its end: http://www.jeepstrokers.com/forum/viewt ... =34&t=2671

[6TIME]

I checked and double checked all the valvetrain when the motor was setup. Rocker rub patterns were checked on the valve tips to obtain proper pushrod length. Then all potential binding areas were looked at for clearance. Definitely No binding anywhere. I'm currently running a different rocker setup than probably all of you tho. I converted the stock rockers to an adjustable stud setup with guideplates. That ran happily in the 4.0 for the 76k that it was alive. I also ran some 1.7 rockers out of a gm 250 they worked fine as well.

[Cheromaniac]

Thats with a stock cam. You throw an after market cam in to the equation and things change. More lift, more duration, more spring pressure. Not to mention how much taper is ground into each different cam. Besides the taper keeping lifter rotating it also helps keep the cam in the block.

You do have a good point there Chris and it makes me wonder if it's the aftermarket cams themselves that are causing the bearing failures. You just don't see them with the stock cam.

]Thats yours. Mine has been around 40psi @ hot idle w/10w30. Maybe your bearing clearances are larger than mine

That's quite possible. My hot oil pressures with the standard pump were 20psi idle and 45psi above 2000rpm and after I swapped in a HV pump, they rose by 25% which is in keeping with the 25% higher volume of the HV pump.

[wjtom]

has anyone sent a set of bearings back to the bearing manufacturer to see what they say?most companies i have dealt with are more than willing to help out when there is a problem.especially if you explain it is somewhat widespread.

[scalper]

how is the runout on the cam?mine did this and found out the cam runout was out 3 thousants to the side.

[92tank]

i dont want this thread to go in a different direction but, what if (if its possible) we could run needle bearings in place of the stock? i know it would take more machining to the block but if it would help cams/bearings last longer it would be worth the time. just a thought on how the fix this problem.

[SilverXJ]

You would need to have a hardened cam with hardened journals. I'm not even sure using a cast cam would be a good idea w/ roller bearings. More harmonics in the valve train as well. The block bore would have to be enlarged to accommodate the roller bearing shell, but is there enough room in the oil galley for this w/o blocking flow? The cam journals would also have to be cut down to all the same size the correct size for the roller bearing. I also heard that they don't like idling very much. I don't know if its due to the roller bearing itself or if its from lack of oil splash. A small hole could probably be drilled in the shell for oiling, like maybe only .010" or less.

[SilverXJ]

Any updates on this?

[6TIME]

Update! It's been a while. I got all the rotating parts back from the machinist yesterday. They also checked my cam journal surface with the profilometer. They said the surfaces on the Lunati were way out of spec for surface roughness/Ra. The journals measured over 30ra and that was even on the rearmost journal that had minimal bearing wear. Clevite says they recommend a 10ra or less for cam journal finish to provide reliable bearing service life with 15ra being the upper limit. So, they polished my Lunati cam and measured a 4ra on the journal surfaces. Now the motor is going back together.... He was confident that this is the problem with my cam bearing wear. We will see..

[Brian E]

Any chance of you guys posting up what brand of cam bearing you use so we can track if there is any brand having a bigger issue? I just tore mine down, my last set did not fail but they looked a little rough with 6000 miles on them so I replaced them.
I am now doing a cam swap to a smaller lift cam "more daily friendly" and the bearings look a little shinny in the bottom region on 2 and 3 bearing again. Cam looks fine, I do not see Babbitt or copper but I think for piece of mind I will replace again.
Seat 108-111lbs .655 to coil bind, open 285-290lbs at 490 lift. My cam lift was 493 comp ex and intake was 477. I am going to a 232 this round with roller rockers. Fingers crossed. Hope your Lunati holds!

[SilverXJ]

I tried several different brands with the same result. This time I have a coated set in and they are holding up at 3147 miles on it. However, I have also done several other modifications so I can't say if its the coating that is working.

[gonridnu]

The majority of cam bearings sold in the U.S. are made by Clevite or Dura-Bond which was just purchased by Melling. I Believe Dura-Bond only makes cam bearings and may even supply Clevite with some of their less popular numbers. As I noted in my build Dura-Bond has an improved design bearing that is fully grooved on the backside so you can rotate the oil hole into the perfect position for providing maximum cam loading. Here is a link to the AERA Tech Bulletin.

http://www.mellingdurabond.com/Portals/ ... lletin.pdf

Silver, did you ever determine if the oil pump mounting surface had anything to do with that?

[SilverXJ]

Here is a link to the AERA Tech Bulletin.

http://www.mellingdurabond.com/Portals/ ... lletin.pdf

Going off that document, which I have seen before, the cam bearing hole is already in pretty much the idea location. http://www.jeepstrokers.com/forum/viewt ... 604#p19604

Silver, did you ever determine if the oil pump mounting surface had anything to do with that?

Unfortunately, fixing the pump mounting issue didn't fix the bearings. I believed they failed again two times after that.