Hihg temperature or detonation?

[Tico]

In my little experience racing Fiat/Lancia engines, if you don't want to have problems, you better have water and oil temperature below 90ºC, specially oil, as pressure drops significantly as temperatures rises. That, in a Lancia Beta even with modified sump, is killing the bearings very fast. That's why I had to use 2 oil cooleres in the Lancia Beta to keep the temerature about GC recomende 85ºC, add an accusump and end of the problem.

But now I am racing a Fiat 131, and found very different kind of problems. It has the modified sump, accusump and no bearing problems. As the engine compartment is more roomy, the air flows thru the coolers better, and only one oil coller of 13 rows is enough to keep the desired temp. It's CR aprox is 10.5:1, almost the same from the Lancia, but if you use the same gasoline, the head gasket blows away. Temperature is runing a little higher than in the Lancia, that is 90-100ºC, but if you use higher octane gasoline (mixing it with aviation) then the problem is resolved.

The thing is that this gasoline was banned where I am competing, so we have to use road gasoline, wich unfortunadley here that means no more than 95octanes.

The car started to malfunction at the end of the race with temperatures showing 100ºC water and 90ºC oil, and when we opened the head found this (look at the picture).

I am also worried of how the material of the head is showing very little holes, hope you understand me seeing the photo.

Would this be because of detonation or high temperature? I cannot't hear a detonation from the engine when is running, but the car is very loud.

Excuse the photo quality but I am trying to show what i am wtriting and easy download

[Guy Croft]

That is classic detonation. You say the temperatures are OK with high octane fuel.

Can't you use octane enhancer?



GC

[CraigAPD]

Is ignition advance not adjustable?

[CraigAPD]

ALso, im not familiar with this engine in particular, but maybe Guy will know better...those temps DO seem a bit high, to me at least. And given the head gasket failure whhc looks like detonation orientated, I would think reducing the coolant temp around the head, will reduce the onset of detonation.

[idv]

Is it the correct head gasket?
The exhaust should have the bigger water holes, not the inlet. Your picture shows the exhaust with the smaller water holes.
Remember the newer (8Vturbo) heads had the exhaust/inlet swapped around. It is easy to get the gaskets mixed up.

Ian.

[Guy Croft]

I think you're right, Ian. Doesn't look like GC supply gasket either..

GC