So I got my timing chain kit put in. new head gasket and sent the head to a pro machine shop that also builds engines. The man that put my engine back together has been doing this over 35 years and had just done his brothers 94 240sx. My car ran flawless for 2 days. I was almost at a complete stop going over a rail road and the car died. I pulled the spark plugs and they where black. we pulled it to his house. checked timing,put in new plugs. fired it up and the engine was shaking and bogging. we heard a tap tap every 3 to 4 seconds. we pulled the valve cover and found my exhaust cam was broken in half. This engine has had several temp spikes due to a bad t-stat and air pockets in the cooling system due to me adding coolant. I've heard that lots of ford escorts that ran hot are none for braking cam shafts. what do you guys think happen?

No one wanted to answer this til now? Well I'm assuming you've re-done the head by now so I'm wondering what you found, in my experience, cams break for two reasons:

1. Lack of lubrication. I broke a cam in an engine once that was a new (to me) car. The previous owner neglected it and I think just topped off the oil without changing it. The day I got it I replaced the lifters and the insides were thick with black oil... cludge. I put it back on Mobil 1. When I took it back apart after the cam broke, the insides were all shiny golden brown again. The Mobil 1 had cleaned all the solidified old oil off and in the process clogged an oiling passage for the cam. I had to pry out the chunk of the broken cam.

2. When guys get a head in to be rebuilt they naturally want to resurface the gasket area to flatten it out. This is fine so long as you also RE-CENTER BORE THE CAM JOURNALS. Think about this, at the factory your head was made nice and flat and a machine bored out the cam journals/caps to be absolutely parallel to the head. Fast forward to your first rebuild, with the head torqued, it's still flat, when untorqued, it can warp a bit from heating and cooling cycles. If you resurface the head now, the cam journals won't be linear and parallel to the head when it gets re-torqued to the block. When you strap in a new cam, depending on where material came out of, the cam will be bolted down in some sort of arc pattern. As it turns, it is the same as bending it back and forth 3k times/minute or whatever for as long as you drive. Even if it's a small amount, the fatigue will cause the metal to fail over time. Maybe the cam had a defect in it already during manufacturing, now it's made worse by this effect.

Experienced engine guys will know this, but center boring and getting oversize bearings adds cost that customers view as unnecessary sometimes. I'm not blaming your engine guy, just saying this happens sometimes. Lots of people will resurface the head without doing this and won't have any problems, then once in a while, you have a problem.

I broke a cam once. I resurfaced my head and had the seals changed but I let the head sit for a couple weeks or so. When I went to install the head I torqued the head on and proceeded to install the cams , well when torquing the cams down I heard a *pop* sound. The cam broke. I couldn't understand it. I followed procedure to the letter anyhow upon further inspection the cam buckets had thin layer of surface rust causing them to react with the aluminum head and freeze in the bucket bores. Instant snappy snappy. Maybe yours wasn't seized but there was enough friction to cause fatigue and then failure.