What is a normal cause of a #3 cam bearing failure

[JDSfastGN]

Ok, I just heard about my motor. Here is the story, I was running the car at about 4700 in first gear, and right before the shift the motor made a loud clacking sound. Well after taking the valve cover off the first 2 rocker arms on the driverside are moving up and down with a lot of room to spare in between the pushrods. (about an .5" of and inch of play) Well we pull the motor(its a fresh rebuild with 13,000 miles on it) and send it to the shop. They said the # three cam bearing was gone , and that I must have run it low on oil. But i never did, I always changed it every 2000 miles and had changed it the day of the incident. The motor has a high volume oil pump, and always is checked to make sure its at the proper level. What is a common cause for the #3 cam bearing failure? Is there something to do with the oil passages or what?? Thanks a lot.

 

[750H.P.V6]

You mean the #3 lobe right?

JD,

I think there must be some confusion between you and the machine shop. My guess is that they said the #3 lobe is worn off the cam right? It is actually pretty common and is more than likely not your fault.

In most Buick blocks the #3 exhaust lifter bore is mis-located in the block. The lifter doesn't spin properly and that lifter/lobe wear at an accelerated rate. Some cam/blocks are better than others and some are worse. This problem is only made worse by cams that have agressive ramp rates and stiff valve springs.

If all the other lobes look fine then the failure wasn't you're doing. Hope this isn't too confusing.

Good Luck

Neal

 

[JDSfastGN]

No all of my cam bearings are really scrorched one has been burned and the block is hurt bad where one locked up (the #3), I'm not sure if its repairable or if i have to get a new block, 3 lobes are flat on my cam. Thanks, for the reply I wish it was just a #3 cam lobe.

 

[JDSfastGN]

Anybody???????? I know its an oiling problem but what actually could have happened?? It has the highvolume oil pump and front cover from ATR and I always ran a PF52, 5 quarts of castrol, and the lifters were always quiet unless the car had sat for a month or more, during my tranny rebuild, and a couple lifters took a while to oil up right at start up. Thanks

 

[750H.P.V6]

JD,

As a question; What do the rest of the bearings look like? The reason I ask is that in the Buick V6 the cam gets lubricated first. This would mean if the failure was an oil starvation problem the rod and main bearings would be wasted too.

Neal

 

[87SFI]

Your bearings are scorched because of all the metal that was going through it when you wiped the lobes. I went through this before and got a roller.

George

 

[JDSfastGN]

I don't know I haven't seen the main bearings i don't think they have it torn down all the way, i am supposed to hear from the shop today, hopefully thanks a lot.