6cyl engine overheating in my '66 F250

Maintenance/Repairs
1

My engine recently spun a bearing and had to have new crank shaft installed with new bearings. Now the reassembled engine overheats. I’ve tried a new water pump, thermostat, switched radiators, burped air out of system, replaced antifreeze, all with no satisfactory results. No steam comes out of the exhaust but don’t know whether the rebuild person changed the head gasket. The manifold heat control valve seems to be operating correctly.
Would a reused old head gasket cause the engine to overheat, even though there’s no steam from the exhaust?
Looking for remedies to stop the overheating.

2

Did it overheat B4 the spun bearing episode?

Can you verify the temp gage accuracy, or what indicates overheating?

How much of the engine was disassembled to change the crank?

3

They probably did NOT take off the head and just worked from the bottom of the engine.
So, you may very well have additional isssues not addressed from the bottom end work.

4

Pull the top radiator hose and check the thermostat. It may be installed backwards.

5

Assuming it’s not a gauge error, what about a faulty fan clutch or missing fan shroud?

6

I’ve gotten defective new thermostats in the past.

Try removing the thermostat and then run the engine. If the engine doesn’t overheat it’s a defective thermostat.

Tester

7

It could be the head gasket if they pulled the head off. They would not reuse the old head gasket, but they could have used the wrong head gasket or installed it wrong. There were some inline 6 cylinder head gaskets that looked symmetrical front to back, but if they were flipped longitudinally, the holes for the water jackets would not line up properly. You need to ask the mechanic if they pulled the head or not.

In 66, there were two 6 cylinder engines, the 240 cu in and the 300 cu in. They were basically the same engine block and heads, but sometimes in engines that are basically the same, the water jackets don’t always align, so the head gasket might be different, but I had a 240 cu in engine in my 66 Galaxy and I seem to remember something about a warning to make sure the gasket wasn’t flipped longitudinally.