Cam bearing failure

[dirtdudeaz]

I discovered this week that I have been driving for a while with half my total lobe heights gone on the cam and chewed up bearings. I hope I found it in time because it's been running 'OK', just felt like a lack of power with a slight random puff every now and then from the exhaust.

I had pulled the head to do some porting work and thought I would check cam timing to see if I could trace the lack of power. After about 2 hours of measuring and playing with the degree wheel, I determined something was wrong and pulled several lifters and took a video as the engine was spun by hand; found the wiped lobes and metal chunks floating in the oil. Hopefully the rest of the engine isn't trash.

Fast forward to Sunday I was playing with the head on a friend's flow-bench and forgot to pull the valve seals from one of the cylinders before a run. I noticed that from .400" and up lift, the spring retainer bottom was hitting the valve seals. That means every valve actuation, my cam lobes were seeing what is essentially coil bind from .400" through .500" max lift.

Not saying this is your cause, but it goes to show everything on the valve train should be checked/double-checked, and trust-but-verify reputable shop's work as well.

[Mike B]

Keep us posted. I have a sneaking suspicion I have a similar issue. What did your oil look like?

Looked like it had a bunch of fine metal in it, too much since break in was over.

[Mike B]

I discovered this week that I have been driving for a while with half my total lobe heights gone on the cam and chewed up bearings. I hope I found it in time because it's been running 'OK', just felt like a lack of power with a slight random puff every now and then from the exhaust.

I had pulled the head to do some porting work and thought I would check cam timing to see if I could trace the lack of power. After about 2 hours of measuring and playing with the degree wheel, I determined something was wrong and pulled several lifters and took a video as the engine was spun by hand; found the wiped lobes and metal chunks floating in the oil. Hopefully the rest of the engine isn't trash.

Fast forward to Sunday I was playing with the head on a friend's flow-bench and forgot to pull the valve seals from one of the cylinders before a run. I noticed that from .400" and up lift, the spring retainer bottom was hitting the valve seals. That means every valve actuation, my cam lobes were seeing what is essentially coil bind from .400" through .500" max lift.

Not saying this is your cause, but it goes to show everything on the valve train should be checked/double-checked, and trust-but-verify reputable shop's work as well.

As far as this issue goes, the head i have was put together by a shop, the valve seats were machined down in an effort to eliminate coil bind. Im fairly confident that this is not the issue.



A quick update, block is finally done, I just need to go pick it up. Apparently the cam bearings were installed incorrectly, they were put in at the 2 o'clock position, but since these are the durabind oil control bearings, clocking should have been offset to better lubricate the cam bearings. Let's hope this shop got it right. Ive heard a bunch of good things about this guy from others, so.....

[Mike B]

Got the block back, set it up so that the cam bore was vertical, and slid the cam in after lubing it up good. I got a good feeling this time, cause last time it didn't spin so nice. Im fairly certain that the bearings got messed up upon installation. Whenever I have time, ill get the engine fully assembled and report back. Ended up with all new seals and bearings for rods and mains since the other ones had all that crud going through them. Fingers crossed that this rebuild is the last for my time with the engine.

[KarmaKannon1]

Got the block back, set it up so that the cam bore was vertical, and slid the cam in after lubing it up good. I got a good feeling this time, cause last time it didn't spin so nice. Im fairly certain that the bearings got messed up upon installation. Whenever I have time, ill get the engine fully assembled and report back. Ended up with all new seals and bearings for rods and mains since the other ones had all that crud going through them. Fingers crossed that this rebuild is the last for my time with the engine.

Good luck. Putting an engine together "for the last time" is a goal I can get behind

[stroked88]

You might check your motor mounts when you go to install. I had my cam bearings wipe from the block flexing because the cheap motor mounts I used weren’t dimensionally correct and I had to pry the motor over to get it to set in. Changed the bearings, used brown dog motor mounts and plates, and never had another issue.

[Mike B]

You might check your motor mounts when you go to install. I had my cam bearings wipe from the block flexing because the cheap motor mounts I used weren’t dimensionally correct and I had to pry the motor over to get it to set in. Changed the bearings, used brown dog motor mounts and plates, and never had another issue.

I've got ironman Andy's mounts, just as good as brown dog mounts. Although, I am intrigued by the plates. I may get those eventually, would be nice having piece of mind, I know of a few people that have sheared the mount plate bolts.

[Russ Pottenger]

I discovered this week that I have been driving for a while with half my total lobe heights gone on the cam and chewed up bearings. I hope I found it in time because it's been running 'OK', just felt like a lack of power with a slight random puff every now and then from the exhaust.

I had pulled the head to do some porting work and thought I would check cam timing to see if I could trace the lack of power. After about 2 hours of measuring and playing with the degree wheel, I determined something was wrong and pulled several lifters and took a video as the engine was spun by hand; found the wiped lobes and metal chunks floating in the oil. Hopefully the rest of the engine isn't trash.

Fast forward to Sunday I was playing with the head on a friend's flow-bench and forgot to pull the valve seals from one of the cylinders before a run. I noticed that from .400" and up lift, the spring retainer bottom was hitting the valve seals. That means every valve actuation, my cam lobes were seeing what is essentially coil bind from .400" through .500" max lift.

Not saying this is your cause, but it goes to show everything on the valve train should be checked/double-checked, and trust-but-verify reputable shop's work as well.

As far as this issue goes, the head i have was put together by a shop, the valve seats were machined down in an effort to eliminate coil bind. Im fairly confident that this is not the issue.



A quick update, block is finally done, I just need to go pick it up. Apparently the cam bearings were installed incorrectly, they were put in at the (2 o'clock position) but since these are the durabind oil control bearings, clocking should have been offset to better lubricate the cam bearings. Let's hope this shop got it right. Ive heard a bunch of good things about this guy from others, so.....

If I understand you correctly you mentioned previously that the oil hole was put in the 2 o’clock position.

Just to be clear ideally they should be in the 2 to 3 o’clock position.

[Mike B]

I discovered this week that I have been driving for a while with half my total lobe heights gone on the cam and chewed up bearings. I hope I found it in time because it's been running 'OK', just felt like a lack of power with a slight random puff every now and then from the exhaust.

I had pulled the head to do some porting work and thought I would check cam timing to see if I could trace the lack of power. After about 2 hours of measuring and playing with the degree wheel, I determined something was wrong and pulled several lifters and took a video as the engine was spun by hand; found the wiped lobes and metal chunks floating in the oil. Hopefully the rest of the engine isn't trash.

Fast forward to Sunday I was playing with the head on a friend's flow-bench and forgot to pull the valve seals from one of the cylinders before a run. I noticed that from .400" and up lift, the spring retainer bottom was hitting the valve seals. That means every valve actuation, my cam lobes were seeing what is essentially coil bind from .400" through .500" max lift.

Not saying this is your cause, but it goes to show everything on the valve train should be checked/double-checked, and trust-but-verify reputable shop's work as well.

As far as this issue goes, the head i have was put together by a shop, the valve seats were machined down in an effort to eliminate coil bind. Im fairly confident that this is not the issue.



A quick update, block is finally done, I just need to go pick it up. Apparently the cam bearings were installed incorrectly, they were put in at the (2 o'clock position) but since these are the durabind oil control bearings, clocking should have been offset to better lubricate the cam bearings. Let's hope this shop got it right. Ive heard a bunch of good things about this guy from others, so.....

If I understand you correctly you mentioned previously that the oil hole was put in the 2 o’clock position.

Just to be clear ideally they should be in the 2 to 3 o’clock position.

That is correct, the originals were installed at 2 o'clock.

The guy I just got the block back from did his own research and found that with the durabond oil control bearings, there is a more ideal clocking position for those. That guy is the expert on the matter, not me, so he installed them as per the direction he found. Going by that, the last bearings weren't in the correct position, but I dont think that was the cause of the failure in the end.

It had been so long since I did the original install, but it seemed like the cam had some rolling resistance when I originally installed it.... but that was also I nthe middle of winter, I had used assembly lube on the cam bearings and it was thick. So it could have been that playing tricks on my mind, but again it was so long ago that I can hardly remember.

[Russ Pottenger]

Sounds good.
Just clarifying the information.

The proper Camshaft procedure should be that The front and rear can bearing be installed first. Then the camshaft clean and dry be installed and should turn freely. Then repeat by installing the third bearing verifying the cam turns freely after that then installing the fourth bearing.

That way it’s easier to isolate which of the 4 cam bearings are tight rather than installing all four bearings and trying to figure out which one is the culprit.
Just know that the camshaft should turn freely with no lube on the cam or bearings.

With that said glad to hear that you found your problem.

[Mike B]

I've got the engine turning again, so far so good. I ended up advancing the cam by 2 degrees, that combined with 4.56 gears, I have plenty of torque now. Hoping that I dont have another failure at this point, I like how the engine works but ill go another route if it does fail.

[Randy Bobandi]

I wonder if shops are aware that the 4.0L cam journals are all different diameters. They decrease in diameter, from front to back by .010". Maybe the shop just slammed them in by random order.

[TR1Hemi]

Cam flex. Your problem will be back.

Cam bearings #2 and #3 do all the work for cylinders 2,3,4,5. Bearings #1 and #4 act as fulcrum points. It always starts at 2 or 3, you caught it due to a leak before it spread to 1 and 4.

Stock springs are 70#S/200#O, there is absolutely NO reason to go over 85#S - 225#O, the only reason spring changes are REQUIRED is to accommodate lift with out coil bind, which is really hard to do with out a spring seat depth change. Believe it or not I am running stock 90's 2.8L/3.1 Chevy V6 springs.

[Mike B]

It's been several months, and I've pit some harder miles on the jeep this time around, though I now have 35" tires and 4.56 gears in the axles as opposed to 33s and 3.55s. I have none of the knocking that I heard before when I had the bearing failure initially. I do however still have that pesky RMS leak, I'm starting to believe the only correct way to install the seal is after the crankshaft is installed in the engine, then to slip he seal in behind using the plastic shoe they give you. I feel like the lip rolls over if that seal is installed before the crankshaft. Ill get that taken care of eventually, it's not that bad of a leak that it's in dire need of replacement. I've got electrical issues that stem from a little bit of deep water treading. But when I do get to that rms leak, I'll take a look up at my cam bearings again to see what the prognosis is, hoping that I'm happy, otherwise I'll probably just torch the engine and figure out what type of v8 to swap in.