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over heating 405

Last year I put the old Ken Evans 405 back on the road, with an engine from an insurance right off. The engine’s block was cleaned and the pistons fitted with new rings. I also fitted a 2mm head saver gasket from I.N. It ran fine but burnt oil so badly you couldn’t see behind you when reversing. I pulled the head and fitted new pistons with 3 piece oil control rings. It runs fine and doesn’t smoke, but once round the block and the water is at 90 C, and if left idling it boils and blows out coolant, that is when I shut it down. All the hoses and radiator are hot, so is the weather and me. Any ideas on what could cause it please as I would like to take it to heritage trust on Sunday. The compression was at 140 psi with the 2 mm gasket and 150 with the 1.6. I would hardly have thought that change in compression would cause the problem. Kind regards. John. A frustrated 405 owner.


I had this problem with my 405 from first getting it. Removing the thermostat helped but I wasn't happy about doing that.  Decrudding the engine, fitting a 4 blade fan, new water pump from Brian May, and recored radiator didn't help at all. Interestingly engaging overdrive worsened the situation! An electric fan certainly helped in heavy traffic and very hot weather. My problem wasn't as bad as yours but it certainly niggled.

Then a few years ago the engine had to come out and we fitted a lot of new goodies including forged pistons, new head gasket and 2mm spacer all from INRacing. This improved the temperature! A bit later we had the radiator recored again and all problems were solved! The engine now stays between 70 and 80° depending on weather and the oil pressure starts at about 100psi cold and goes down to 50 to 60psi hot.

I don't even need the electric fan now except for very recently when the fan belt broke and I had to use the electric fan to keep the temp below 100° to allow me to get home!


My problem turned out to be the routing of the top hose. It was looping up and down again, I suspect air locking. I twisted it to keep it level and problem solved.

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Michael Brooks