I was thinking about this, and I know this topic comes up ALOT, so I thought I would take a logical aproach to this.

Swapping a cam could only cause bearings to go south if one of a few things happened....

1: Scarred bearings from install or dirt
2: The bearings could not handle the RPM
3: The bearing surfaces did not mate properly

Now the 1st 2 are talked about alot and the 3rd came through reasoning. Why would a new cam cause any problems unless the oil couldnt get to the bearing surfaces? You are just swapping out a metal shaft. The journal and bearing surface must have some reasoning. 99% of cam swaps involve spring swaps and 99% of the time they are stronger springs.

Could it be that this added spring pressure caused a problem with the bottom of the cam bearing?

I thought a possible solution could be a proper "break in" to the cam using lower ratio rocker arms to reduce pressure on the bearing surfaces and give them more time to mate with the journal. Combined with a clean install and a modest powerband increase, it should allow the bearings to last.

Any thoughts on this?
-Stu

 

Hmmm, sounds like a good idea to me. I'm thinking the biggest problem would be people not realizing how essential it is to be very delicate with the cam and bearing. I have seen a lot of people "man handle" things of this nature. You just can't do that. Also, everything needs to stay "hospital clean" when doing internals on an engine. Many people either don't know that, don't care, or don't care to listen to it. (Not saying anyone here. just saying I'v seen people like this, and I'm sure there are a few of you out there. ) If that's not the case, I kinda like the theory of the added stress of the new springs and rockers before the cam settles into its new home.

 

Here is my opinion on why it happens so much:
1) you are right on the cleaning issue. Also VERY important to keep coolant out of the oil. Nothing will take bearings out faster than coolant.

2) after paople get there new cams in they think they can now spin it to 7000rpm without and consequences........WRONG!!

3) on higher mileage motors the cam is worn in to the cam bearings. Installing a new cam takes it toll on the cam bearings , causing a lot of wear fast and even scoring them. This results in metal in oil as well as oil pressure loss. Either one by themselves is enough to cause rod bearing failure. Together it is bad news...

 

Thats exactly my point why I think lower ratio rockers would help here.

 

You seem to be assuming it is the cam bearings that fail. It is most always a rod bearing. I don't think I have actually seen a thread about cam bearing failure, though I know there have been some describing worn bearings.

From my own experience, I blame it on lack of enough oil pressure to support the higher RPMs that you will visit more frequently with the new cam + amount of engine bearing wear already present.

 

I swapped out my cam two years ago. At the time the motor had less than 75,000 miles on it. Late last year one day I started up my car and I could only get 25psi when driving around (4K RPM and under). I'm hoping that it's my sender going out on me, as I would think that if there was a problem with the bearings, it would have went out a long time ago.

 

Good points. Are you saying that cam bearing wear is causing decreased oil pressure, thus not oiling the rod bearings at high RPM which ends up destroying the rod bearings?

Would the excess wear cause too much clearance? How would this be any different than a stock cam? Is the oil pressure going to be the same, it just doesnt have enough pressure at high RPM that a new cam is going to rev to?