A while back, a friend of mine had his 1992 Accord just die on him on the freeway. Knowing that Honda ignitors have problems, I figured I would just slap in one of my spares for him. But when I was replacing it, I noticed that, when he cranked the engine to try to access the rotor screw, the rotor wasn't turning. My first instinct was that he broke his timing belt. But when I checked it, it was perfectly intact! So I had him crank the engine again to see if the distributer is just broken. One second, it looked like the cam was turning. The next second, it wasn't. But I was just looking at different parts of the cam both times. And it turns out it is broken between the 2 and 3 cylinders. What could cause this to happen? I guess it doesn't matter too much, considering that his engine also looks like it has suffered some degree of oil starvation, and will need to be replaced. But I have never seen or heard of a broken cam, at least in a 100% bone-stock car. It seems like, even if a cam bearing seized up from oil starvation, the timing belt would sooner snap than the cam would break.

 

It's hard to say really. He'll need a new head. Maybe that came wasn't made to be as good as the other OEM cam for that engine when it was being made.

 

Hard to say whether I would want to just slap a head on his engine. He basically told me that he drove it for a while with the oil light on. And, although your top end will generally go dry before your bottom end, I just don't trust it. Plus, when you weigh the cost of a used head and all the gaskets against the cost of a used long block, the difference is not really THAT big.

 

I large cam destroying monster from Mars. Maybe a hairline crack in the casting?

 

Could have been a bad casting from the factory, or, the fact that oil pressure was low caused more drag on the camshaft and it snapped.

 

lack of oil changes and valve adjustments probably out of timing too.

 

Starving the top end of oil is what snapped it. Burned the bearings, creating excess heat and fatiging the metal causing it to break. One half tried to weld itself to the cam journals while the rest tried to keep turning.

 

I still can't see how a fairly hefty chunk of steel (ie the cam) would end up breaking before the timing belt. I would think that, if the cam seizes, the first thing to break would be the timing belt.

 

Probably a combination of heat from no lubrication, a manufacturing defect and the shock from the valves.

 

The timing belt is pretty tuff. Think about how fast and and how often it has to change torsional forces when you step on the gas and let of quickly. Now multiply that over 100,000 miles. You have the timing gears that allow leverage to turn the cam against spring perssure. A lot of newer camshaft are hollow as well to allow oil thru to feed the valves and springs. Have you pulled the cam out to see what it looks like at the break? if its discolored, that can tell you.

 

^ x2

You have the best vantage point for finding out what the cause was. Take the valve cover off, remove the rocker assemblies and look at the cam and cam journals. That will tell you more than anyone that is merely guessing at the possible cause.

This is not a common occurrence so it's not like there is a wealth of actual knowledge as to what may have caused it. it is only obvious to assume that it is due to the oil light and probably oil starvation and overheating/galling of the journals.

As far as the timing belt breaking before the cam.... that may become more obvious once you take a look at the condition of the cam.

 

Right here.

 

I was going to say "HULK SMASH!" myself...

I see what you did there, cam breaks timing is now off.

In all seriousness, there were probably several things wrong with the engine besides cam and/or ignition timing. One being...

Simply it **** the bed due to abuse. No oil = all sorts of interesting ways to end an engine.
Wouldn't spend any money on that old assembly;
Smack your friend upside the head, get a used engine,
Smack him upside the head again, replace old engine,
Fake out friend and backhand him, start new engine.
If the dipstick ever shows no oil, whip him with it.

Lesson learned.