Why did my exhaust cam break?

[chris1212]

Long story short. engine temp spiked more than a few times bad t-stat.So the HG went bad.Very low miles on a fresh new build and head job. Was coming to a stop and the car dies. Exhaust cam is broken in the middle. The car was running flawless, head was done by a professional shop and put together by a shop with over 35 years of building engines. Anybody have any answers?

[mechanicalmoron]

one of the bearings siezed, and something had to give.

Did you take it out? I bet one of the back bearings is nearly friction welded in place, it got too hot and/or oil starved, and smoked the oil that was in it, and froze up, and something had to give, so it sheared along a pre-existing fault/abnormality.

Though I'm not sure how your timing chain and sprokets didn't rip out.

[chris1212]

what back bearings are you reffering to? Id like to know everything that needs to be checked before we put in another one today. Do you mean the end of the cam is spinning with a bearing? I didn't notice. The front half of my cam was still spinning. the car will cranck but ofcourse not on all cylinders so it's boggy..this happen really at ideal speed and the car shut off really fast because it smoked my spark plugs. I hope it didn't hurt to much.The cam broke in the middle at a oil journal

[chris1212]

you must mean in between the cam caps and the cam

[mechanicalmoron]

Yes, the journal bearings.

If the came broke something obviously changed the speeds that the different ends where turning.

Or maybe you have a buggered valve.... and a buggered cylinder to match.

[chris1212]

I should know in a few hrs.

[asoomal]

I don't believe that they have bearings...

[blkvrtswp]

Other possibilities:

- warped head from overheating (I would think it would have to be really warped to distort from the bottom to the top, but maybe)
- cam towers not replaced in correct factory order causing binding (pro shop unlikely to do this)
- defective cam

[chris1212]

OK fellas. this was my exhaust cam. It didn't seize up on a oil journal due to oil starvation. This engine has seen it's fare share of temp spikes due to 3 bad t-stats from auto zone plus it got hot when my factory fan took a crap..So come to find out it had a crack in the middle in a crease that made from the factory. It finally gave..The shop just called and siad it's running fine with a cam I pulled from my spare engine.

[mechanicalmoron]

I don't believe that they have bearings...

Not to be a jerk, but what exactly do you think a bearing is?

[asoomal]

?

[mechanicalmoron]

?

A bearing does not need to be removable. If it had no bearings, the cam would NOT turn.

Op says "oil journal", which is close enough. They're hydraulic journal bearings.

[asoomal]

Ahh I see, always thought they were just called bearing caps.

[fiznowler]

?

A bearing does not need to be removable. If it had no bearings, the cam would NOT turn.

Op says "oil journal", which is close enough. They're hydraulic journal bearings.

i am still asleep. I was thinking crank bearings lol