Just a query I'm running nos on my vk v8 calais can I use avgas with the nos or will I have the pistons melting?

Depends on the amount etc... Avgas does have more energy per litre than petrol, the agents/sellers of the N2O should be able to advise with more precision,

avgas is slower burning than pump gas, it will be a good thing for you, as always tune it well and you will be fine.

so are you saying a lower burning temp?

I thought avgas burnt hotter?

longer chains means slower burning rate, higher energy per volume which might well suggest hotter burning - it all depends. A revision of engine advance at least is essential !

hmmm but when running nos (150 hp) a 4 to 6 degree retard is required with colder plugs?

thats right, with avgas less advance - ie Not as much as for petrol N2O I cant be sure, never run it myself Some original photos have not been recovered yet.

Avgas has less energy compared with std pump gas, it burns slower, therefore requires MORE ignition advance, the key to high octane fuels is their ability to resist knock more, If you have an engine that is tuned 100% perfect on say 92 octane fuel and then change to avgas, you will loose power. where you gain it back is adding more boost / timing to the equation. I have used around 3000+ litres of Avgas in my car and its horible and lazy fuel, but it does provide a safety margin over pulp when working a boosted motor hard.