which cylinder head??

[Chris KC]

For what it's worth I tried quite a few heads in the past and the Speedex was the one I kept on the car. Ultimately though I felt the compression ratio was rather high, so I reverted to the standard '37 type, which is a good all-round head for road use. Aluminium heads are more prone to warping / distortion, worth considering too.

I am aware of the fact that some people fear warping of an aluminium head but then again AlfaRomeos's had alloy heads as had the great Hillman Imp..... its a matter of treating them right methinks. Torqueing (or is it torquing?) them down properly (not meaning ham fisted) and allowing block and head to warm up..   which is not the same as 'water temperature at 80 degrees centigrade'.  I'm used to that. And I'll be carrying a head gasket in case things do go pear shaped....

Side valve heads are more vulnerable to warping as they have little torsional stiffness. But yes careful management of torque and temperature is appropriate. It depends what you plan to do with the car Michael; I warped an alloy head when I burst two radiator hoses going over the Petit St. Bernard pass, and had to get home with water weeing into the cylinders every time I stopped the engine. This was inconvenient and since then I have stuck to cast iron, for trips further afield at least.

Well Chris....I was not planning bursting two radiator hoses.. the pressure in your cooling system must  have had risen way beyond normal levels .....and as the engine was presumably overheating... in such an obviously quite extreme situation it's hardly fair to dismiss the alloy cylinder head as being 'prone to warping'....  nevertheless.. your posts gives me cause to consider fitting something of a catch / expansion tank and / or a radiator cap that wil allow exces pressure to pop off.....

Michael, funnily enough neither was I! I'm not dismissing alloy heads as prone to warping; merely saying they are more prone to do so than iron heads. Depending on your intended use you may want to factor that into your thinking. There is no pressure in the cooling system, except perhaps momentarily as the contents spew out of the radiator cap when it boils. The incident I mentioned was most likely due to repeated overheating and probably fairly old hoses to start with. Overheating has to be considered likely if you intend driving your car in Alpine conditions, this would be considered extreme by many owners; my car is built with this kind of use in mind.