Why Do Factory Installed Cam Bearings Look Bad

[70rcode]

I remember my 10k mile '69 Hemi Factory Cam bearings surprisingly looking so Pitted-- Erroded Bad looking in '72...... They've pretty much stabilized at that first peek inspection appearance....I remember most Experienced Mopar mechanics advising "Leave them alone" as they're much Functionaly Better than shop replaced ones.....So,... I've left them be...Hearing that Cam bearings are Critical to oil pressure,.....Did Chrysler have some kind of Factory installed can bearing Issues (pre--erroded, chemically damaged ?) going on in '68--'70 build years & How Bad looking is bad enough for required replacement ?? How do you accurately estimate when the replacement hassle (most likely place for bad shop job to occur) headache is worth it ??

 

[Carcinogen]

I’ve had problems with new cam bearings in 440, shop teamed last bearing for clearance

Tight cam bearings

Believe it or not the factory had a large stepped reamer to fix this exact problem on assembly. The cam bores are not perfectly in line in all engines. This is why the service manual specifically says not to replace the cam bearings if they are NOT damaged. The factory line reamed them. A high end shop will have a cam bearing reamer. If the cam is straight this is the problem. So either use a bearing knife, a slotted old cam or find the "big old bearing reamer":

 

[Geoff 2]

I use Dura Bond cam brgs.

 

[70rcode]

I was advised back in the day (1970) by the best Mopar mechanics to leave the cam bearings alone despite looking really bad, as long as oil psi is good/normal.....Is that Still true today or has anything changed ??

 

[Kern Dog]

My machinist told me that the factory installed the cam bearings then line honed them.
If the block goes in the hot tank for cleaning, the bearings will start to dissolve, requiring replacement.
Nowadays, I use THIS to clearance the bearings in a rebuild....

I cut diagonal grooves in the journals and fill them with bearing grease.....then slide the cam in and rotate several revolutions. This is done before any assembly is done so the shavings can easily be retrieved. This will knock down any high spots.

 

[Geoff 2]

I wouldn't leave 'really bad' cam brgs in any engine. They won't get 'better', only worse.

 

[70rcode]

And Why did my 10k mi 2 yr old cam bearings look all pitted tore up with oil & filter changes every 1000 miles Kendall 40 wt + Fram & All other engine bearings looking new, perfect & pristine condition ?? Those cam bearings must have been pitted & corroded condition when factory installed ??

 

[Geoff 2]

Kern,
I doubt the cam brgs were line honed. The surface is soft babbit material, like the rod & main brgs. The cam tunnels might have been L/honed.

 

[70rcode]

Btw,.....Should cast iron block cam bearings be carefully Pressed out & in or Hammered with the correct tools ?? Hammering any cast iron seems so unnecessarily "primitive" & kinda risky.....You never fully know what a mediocre hammer tap is Always doing to cast metal.....I would think a slow, steady correctly aligned Press force would just be considerably safer type process ??

 

[70rcode]

For that matter,....Why Shouldn't new cam bearings be dry ice chilled (to significantly reduce OD size) & then Quickly light Pressed or lightly tapped into heated or room temp engine block ?? Similar to Correctly installed valve seats & other precision interference fitted metal to metal installation procedures assuring proper interference fit with Least collateral Damage to bearing edges, steel tube shell distortion & gouging & cast iron shock damage.....

 

[moparedtn]

Just checked. My '68 FSM says no such thing about leaving originals in the block "if they are not damaged"...
Just the same, any time I've had a block at the machine shop in prep for a build, they have the cam I'll be
using with it, usually with the goal of "spins freely" not "rattles and flops around in there".

 

[bandit67]

I just hammer in my cam bearing as normal. I have done a lot of Chevys but only about 5 large and small block Mopars and have had no known problems with any of them. I have had some "tight" ones, which take some massaging. It usually takes me about an hour or so, I am slow, checking and rechecking one at a time. I was told the factory put them in all at once, took about 15 seconds. I have also knocked out a lot of bearings and not noticed any "severe wear or pitting". But, alas , never had my hands on a hemi. And I have not ever thought I needed to freeze them prior to install, as I have froze and heated some bearing prior to.....
But my stuff has always been street engines, never done a race motor that has seen severe duty on the track.....

 

[69Bee]

STOP overthinking things... You are stressing yourselves out, and giving newcomers misinformation.

1) Cam bearings should be replaced when you rebuild your motor
2) The majority of cleaning methods don't use "Caustic" solution any more and don't require the replacement of cam bearings
3) You can NOT line hone, sandpaper, or any other abrasive method on babbitt bearing surfaces
4) The OEM slammed "Semi-Finished" cam bearing home and followed with a line "Bore" to size them
5) There are no one shot reamers out there to be found with the exception on custom made ones like "Kern dog" showed
6) The proper method to fix tight cams is to scrape the high spots with a bearing knife

The best thing to do to prevent tight spots in the bearings is to do proper bore prep BEFOR you install the cam bearings. When the factory slammed the shells home, it galls the bore and shell quite often, but they didn't care because they were going to line bore them anyway. Use a file to dress the raised metal in the bore, do your best to chamfer the drilled holes, and quite honestly, a final ball hone pass will do wonders. Bearings install better, and I have far fewer tight cams. As far as hammer vs. pull install, I do both and each has it's pros and cons so I use both methods.

 

[69a100]

And Why did my 10k mi 2 yr old cam bearings look all pitted tore up with oil & filter changes every 1000 miles Kendall 40 wt + Fram & All other engine bearings looking new, perfect & pristine condition ??

Can you say Fram? Why you changing oil every 1000 miles? There no need to do it that often! Why do you use such shitty components, i.e. oil filters? I have to wonder what the other bearings look like?

 

[Cranky]

My machinist told me that the factory installed the cam bearings then line honed them.
If the block goes in the hot tank for cleaning, the bearings will start to dissolve, requiring replacement.
Nowadays, I use THIS to clearance the bearings in a rebuild....

View attachment 1305342

View attachment 1305343
I cut diagonal grooves in the journals and fill them with bearing grease.....then slide the cam in and rotate several revolutions. This is done before any assembly is done so the shavings can easily be retrieved. This will knock down any high spots.

View attachment 1305344View attachment 1305345View attachment 1305346

So long as that old cam is true it should work fine...

And Why did my 10k mi 2 yr old cam bearings look all pitted tore up with oil & filter changes every 1000 miles Kendall 40 wt + Fram & All other engine bearings looking new, perfect & pristine condition ?? Those cam bearings must have been pitted & corroded condition when factory installed ??

What was your oil pressure? If they were pitted a little at the beginning, then high psi can possibly wash them out....

Btw,.....Should cast iron block cam bearings be carefully Pressed out & in or Hammered with the correct tools ?? Hammering any cast iron seems so unnecessarily "primitive" & kinda risky.....You never fully know what a mediocre hammer tap is Always doing to cast metal.....I would think a slow, steady correctly aligned Press force would just be considerably safer type process ??

I made my own cam installation tool and have never had a problem. A buddy of mine has one of those universal cam tools and has problems on nearly every ChryCo engine he builds.

 

[Fran Blacker]

Around 1970 Car Craft ran 2 articles called Hoover talks Hemi's. He said to use a cam like Kern dogs to clearance cam bearings. As 69Bee said no abrasives on babbit, they imbed abrasives in the surface.

 

[70rcode]

Oil pressure has always been 70--80 psi depending on 30--40 wt oil used with factory oil pump spring....Has always been my fair weather "machine" & Every outing included 6000 rpm bursts....never daily driver & I just wanted to change oil frequently.....I ran Real soft all babbitt "Micro" main & rod bearings for a while & they always looked barely used with No issues......So I conclude the Factory installed Cam bearings were in this condition when it left the factory..... Realizing almost no one today, has a 10k mi factory engine around, but does anyone remember noticing '60's --70's Mopar with bad looking cam bearings ??

 

[70rcode]

Right on,. Fran.....I still have those 2 "Hoover Talks Hemis". magazine articles....It was in Part 1,. Cylinder blocks section that Tom advised "The cam bearings may look horrible & despite the ugly appearance, replacing them is Likely to worsen the situation". That's where he added "if you do replace (bearings),. the approved method is to clearance them with an old cam modified as a Cutter--clearancer.....I bought those 2 '71 magazines off the drugstore rack & held on ever since....Very useful info in those articles by the hemi "Man".....