Cracked my head!

[greaseball]

I actually cracked it a while ago. I bought a 62 f100 with 12k on the rebuilt motor. I changed the oil, plugs, topped off the radiator, new smithy's glass pack, white walls, and proceeded to enjoy my new daily driver for a whopping 2 weeks before cracking the head while going up our local monster 3 mile grade. I was able to limp my truck home on 5 cylinders. Actually, I more than limped it, it would only run at high rpms so I obliged and was passing people left and right on 5 cylinders. Heck, it's one more than most imports have.

I got home and watched it run (it still idled on 5). There was steam coming from a crack on the head between the deck and the spark plug hole on one of the middle cylinders. It never overheated out of the radiator, and the stock temp guage read cool. Never lost oil pressure but the oil was VERY thin, and looked like it was boiling out of the side cover. Radiator was still full of nice looking green coolant.

I pulled the thermostat and it was facing the right direction. I put it in a pot of boiling water and it opened.

When I first got it, I noticed a bad exhaust leak at the flange and meant to get a new gasket but failed to find one locally. Turns out that it wasn't the gasket that was leaking but a huge crack just above the flange on the exhaust manifold facing the block. Could this be why my head cracked???????

After getting the head off, the spark plug on the cracked cylinder showed typical signs of predetination (probably from racing Hondas home on 5 cylinders). Head gasket looked ok, and the engine did look very fresh with cross hatching still visible on the cyl. walls and no ridge. The old owner kept meticulous records from 1964 until 2000 when he died. He documented the exact mile that the 223 was rebuilt. It's bored .030 over.

I bought a core head and had it rebuilt by John Mummert. I need to finish my fence so I can start rebuilding this thing.

Any tips, suggestions on why my head cracked, etc. is more than welcome. I plan on making this my daily driver so I'm going to have to make friends with that big nasty grade. Heck, it's an old torquey truck right? I don't care how long it takes to get up that grade, just as long as I don't break doing it.

Thanks,
Shane

 

[greaseball]

I finally figured out why my head cracked. I was checking out the humongous crack just above the collector on my exhaust manifold on the side facing the block. I tried to feel the inside of the crack, but it was blocked by the exhaust control valve. Turns out the valve was rusted shut and basically blocked off the center exhaust port. This caused a huge amount of excess heat build-up and eventually the head cracked. This allowed the head and intake to get extremely hot, without causing the coolant to overheat.

Everyone that is running a stock exhaust manifold with the exhaust control valve should go check it right now to make sure that it's not stuck. If it is stuck, hopefully it's not stuck shut like mine was.

The exhaust control valve is supposed to be shut when the engine is cold to direct exhaust gas into the heat riser to help with fuel vaporization. I'm going to go with some clifford headers since I obviously need a new exhaust manifold. Without the heat riser I'll just have to wait a while for it to warm up.

Shane

 

[Cosmotiki]

What a bummer, but glad you ID'd the cause. All kinds of strange things can happen to a 40+ y.o. engine/vehicle, but your research should help out others.