Potential Cam Failiure?

I'm going to say this not to be demeaning, but because I've seen this so many times its second nature.

An machinist is getting called out because he set the guide clearance too tight. While this is possible, that machinist would have to be stupid, lazy or both. It's not that hard to do.

What most likely happens is guys *THINK* it's better to use very late (slow, retarded...whatever you want to call it) timing on intial start up because it's "safer"

Well, it ain't safer, it's more likely to cause an exhaust valve to stick that anything else and it needs to be corrected.

When starting any fresh engine, you want MORE timing than you would normally run, or at least the same amount of timing you would normally run.

For example, if you normally time the engine at 35 total and it's all in by 3000, and you fire this new engine with only 10 degrees on it, and you set break in engine speed at 2000, depending on the timing curve you may only have 15-18 degrees on it.

And that, makes a huge amount of heat. And that heat goes right into the exhaust valves and IDK if you set the with .005 clearance that will stick. Every single time.

What happens is you are delaying combustion so late (and there for you complete combustion late) that combustion is still happening, the exhaust valve opens into all that heat and it gets over heated. And it's happening so fast that the valve can't possibly dump all that heat through the seat. Next thing is the valve gets hotter and hotter, the stem gets bigger and bigger and boom, it grabs the guide.

I'm not saying this is your issue. I'm saying I've seen this happen so many times its criminal. If a machinist sets guide up too tight he should quit the business, because as I said, he is either stupid or lazy.

Just a FYI.