Been doing some more checking this morning,
From cold, with the bonnet open, the front carb dashpot is cold (obviously), till engine warmed up
but as soon as the electric fan kicks in, the heat from the radiator is directed onto the
front dashpot, which starts to get warm, and this is with the bonnet open in a mild
Leaving the engine idling for 5 minutes and it is still the same, closing the bonnet
results in front carb and rear carb and dashpot heating up, (5 mins, ran out of time).
Agreed the manifold on the other side does not help, but I do not remember this with
the viscous fan.
Will check again in a day or two, with a quick shield made up to be held under the float
chamber screw, wide enough to deflect the heat 'somewhere' rather than directly on.
So you have the evidence, once the bonnet is shut, it doesn't matter how good the fan is, the heat can't escape!
Try fitting your louvred bonnet and see just how much hot air escapes through the louvres when the fan is running! I'm betting it will be enough for a barbeque!
Theory says that after the first scalding blast when the fan cuts in, the air emerging from the louvres SHOULD actually cool down as you're increasing the throughput of cold air through the rad and engine bay by giving it somewhere to go (since hot air rises) This is why my preferred place for the louvres is as near the back of the engine bay as possible, ie the highest point, but a double set like Tony's can't hurt as then some hot air can also escape BEFORE it gets to the carbs! Also, the more louvres, the better the airflow!
Of course, if you go the EFi route, you will no longer NEED to worry about vaporisation, get saving, i'm itching to try the Jenvey kit!