2l/3l cylinder head question

[MattF]

Just out of interest Matt what would you do in those conditions ? Crawl up at 15mph ? (getting no air rammed through the rad) Bearing in mind the Spanish roads have hardly anywhere to pull over.

What would you deem to be 'acceptable' performance ?

Bugger. Apologies for not responding to this earlier. Didn't realised you'd edited and added to the post.

With regards to the speed and the airflow thing, it's different in my case. I'm not reliant on the viscous fan. The viscous should perform well enough. You'll never exactly have a low R.P.M at any point. Most tend to say that the viscous outperforms electric fans on low speed grunt jobs.

Acceptable is whatever keeps it moving and doesn't push it past the limits, in my book. You'll still get there in the end.