COO has always run "a bit hot" putting out 96bhp with a standard GT radiator, I fitted a Super 2 Core rad from Sheffield MINIBITZ which made a great difference, however , recently she was blowing water out of the radiator and despite running an expansion tank, she overheated.
Desperate to increase the cooling? Too right I was ..
First I fitted a thermostat blanking sleeve- the existing thermostat is removed to increase flow through the rad, the blanking sleeve stops a hot spot forming in the head between bores 2 & 3, still blew water out but ran cooler
I took the number plate off the radiator grill - that was stopping a bit of air . still ran cooler!
I moved the oil cooler to the right until it was in front of the dizzy rather than the flow to the rad- ditto!
THEN, and only THEN did I think about a possible problem with the head gasket ..logic was
With an expansion tank, steam from boiling water would gas off into the expansion tank, any vapour in the radiator would condense back to water and the vacuum created would suck the water back into the rad from the expansion tank- combustion gases would blow the water out but not cool back down from vapour to liquid to suck the water back, the rad would just be full of gases.
Without a cooling system pressure tester or a combustion-gas-in-coolant detector (these can be bought and use an indicating solution that changes colour if exhaust fumes blow through it) the tracks visible on the head gasket between bore 2 & bore 3 into the water channels was the answer.
The expansion tank works fine now, as the engine warms up the water goes into the tank and as it cools it goes back- REMEMBER never overfill an expansion tank as the water coming from the rad needs some airspace to compress (overfill the exp. tank and there is nowhere for the hot rad water to go!)
BTW 65c thermostats are available from autofactors (I think for Austin 1300s!) If the thermostat doesn't have a bleed hole drill one, if your car doesn't use a bypass hose drill 3 to 5 small holes round the edge of the thermostat to give some flow when it is shut! DO make sure you put the stat in spring side down!)
Just have a look at the temperature gauge on the car as you come to a halt, turn the lights on, turn the engine off, turn the ignition on and off... watch the temperature gauge. I rewired COO and with a bad choice of take off points for the power for the temperature gauge 88c running dropped to 84c with the ignition on to 80c with the ignition off, bog standard mini gauges run off a voltage stabiliser, after market gauges have a built in one, they can go wrong.....have a check before you write one out!!!!
Fat Bloke Tip of the week: replace your flimsy concertina bypass hose with a carefully cut length of oil cooler hose (1/2" bore) this is good to 160c and 120psi, guess water at 120c and 15psi won't damage it!