Engine overheating issues

[toby97]

Hello! I'm after a bit of advise please.

For a few years now we have struggled to solve a major issue on my '66 reg transit custom sport vehicle. When under load or any strain, or when the weather is particularly warm, the engine 'cuts out' whilst driving along.
Day to day basis it happens at 70-80mph.
On particularly hot days it happens at any speed

The temperature gauge will suddenly show over the standard central 90c or whatever that is, and will stay there, whilst the accelerator will rev but the van just decreases in speed (engine doesn't actually stop), until the strain is over (eg, going up a long hill is when it is at its worst)

I don't know if its related, but, recently a problem has got particularly bad - when I put the foot on the accelerator, the engine will lull, and it feels like theres no power transferring from the accelerator to the engine (almost feels like a slipping belt?), and whilst you keep the foot on the accelerator it does accelerate but on and off... this is usually at slightly higher speeds of 40+, and its like a few second lull until acceleration properly kicks in

Sorry for the long message, any ideas would be appreciated! I have been advised its maybe a head gasket issue, but want to seek advise before I pay that.

[APW]

Any good:
viewtopic.php?f=65&t=191961

[toby97]

Any good:
viewtopic.php?f=65&t=191961

Perfect thank you - I'll make a start with the thermostat housing! Thank you