Head gasket 327

Before you decide the problem is head gasket(s), try a little test. Fill the radiator to about 3/4" below the rim where the gasket on the cap seats. Then start the car with the cap off, and watch the coolant in the radiator. If it's blowing bubbles, suspect the head gasket(s).

IF NOT... replace the thermostat and see what happens. Sounds to me like a "standard" overheating problem more than head gasket(s), and if so, there are several things to look for...such as:

** lower radiator hose sucking shut;
** radiator coolant passages blocked;
** water pump impeller not functioning, or rusted/disintegrated;
** blockage elsewhere in cooling system, including water passages in head/block.

If there is compression leaking into the cooling system, you'll see that result almost immediately. If not, look for other cooling system-related problems. Most cooling system problems are related to flow...air flow through the radiator fins, or coolant flow through the block/heads/hoses/radiator/water pump.

Thankyou for the quick replies.

The rad is new since 80 miles.
The stat is new - could be faulty of course.
The water pump was new from Galvin last year, and the drive belt is tight.

Looking at the shop manual this afternoon I realise it's quite light on some procedures. A basic point for example - could I get the heads off with the engine in the car?

And are the exhaust manifold bolts usually rusted solid or would they undo?

Will check the bottom hose.

If you weren't the one who actually installed any new parts RE-CHECK EVERYTHING.  You seem to be determined to do the most difficult and expensive repair when it might not be necessary.

You can remove the heads with the engine in the car. The manifolds should come off, but some of the bolts may be rusted, especially the bolts holding the pipes to the manifolds. You can deal with broken bolts once the manifolds and heads are off... but you will likely be okay.  

check the lower hose and see if it's pulling the warm water from the radiator. I had a bad pump impeller and it would not flow. Some of the original pumps had plastic impellers, or bakelite.