MAJOR MALFUNCTION!

Not sure what to think, or what's wrong, but started the cam breakin today and things didn't go well.
After starting the engine and bringing it up to 2500 rpm's, about 5 min. in the temp suddenly jumped from around 180 to 230 degrees. Shut the engine down and started looking around feeling the block, radiator, etc. for problems. The aluminum heads were hot enough to fry eggs, but radiator was ice cold. Block was lukewarm, and it appears there is a circulation issue.
Never had any oveheating or circulation issues prior to the head change, so of course I'm wondering what might be wrong with them as my first concern. I'll pull the T stat tomorrow to see if it's an issue, but I'd be surprised since it worked before and wasn't disturbed during the head change. Same for the water pump, as it was fine before and was new when I put the engine in last year.
I've never had a problem similar to this where there seems to be no circulation. My temp gauge is in the head, so I'm reading head temp, not block temp or intake manifold temp.
This is a real puzzler to me, as I've just never seen any SBC react this way? If anyone has any clues or guesses, I'm sure open to ideas before I start tearing the heads back off again.

 

Maybe some packing material got in the water jacket. I would start looking into the coolant passages in the heads. Maybe the hole is missing in the gasket? IDK you got a new one for me. Keep me posted for sure.

 

head gasket turned wrong and blocking water passage?

 

Geez, Pete beat me to it! I was thinking the same thing while reading the story.
Your coolant level isn't low, is it?

 

Maybe a big ol' air bubble? I like Camaros idea too. I have had low coolant issues like that.

 

I've gone "oops" with the coolant level before on a new engine. It's easy to get distracted when paying attention to other stuff the engine is doing.

 

I'm going to go with Pete on this one. Sounds like a flipped gasket to me as well. No flow to the heads making them hot, water in the block making it warm and no flow to through the rad making it cold.

 

From reading your posts I'm ruling out newbie issues. You seem to know what you are doing. My alum heads seem to transmit heat faster than the cast. You may have not gotten the heat to the thermostat yet enough to open. Does your temp sensor fit directly into the head or do you have a pipe reducer. The sensor may be getting it's info directly from the metal and not the water.

 

The sensor is direct into the head and nothing but the adapter that it seats into. I doubt I'm low on cooolant as I've got two gallons into the system, plus some water to top it off.
I guess I'll begin to tear it all down again and see what's going on internally with either heads or gaskets.

 

Bingo! We have a winner!

Whew! Boy do I feel stupid today!
I decided I'd tear things down to see if I got the heads gaskets backwards, but checked a spare set first and they can go either way, so no right side up on them. Moved on to draining the fluids and when I opened the radiator it was nearly dry! Seems the cooling system had a air pocket in it, and overnight it settled through and allowed me to add another 2 gal. on top of what was already in the system!
Finished the breakin today, and all went well, but I do notice one thing. The aluminum heads heat up much faster than the block, so the temp gauge pickup in the head gets to about 210 degrees before the 170 degree stat opens. Once it opens everything equalizes and the gauge reads 180 during the run.
Didn't sleep much last night, but I'll sleep good tonight! Thanks for the suggestions guys!