Originally Posted by Karlos G

I run stock 20 year old springs as instructed by Karl Norris and my limiter was at 7200rpm, did many many runs at that without probs only dropped back to 6600rpm because my T3 runs out of puff long before that, also IIRC Tim runs them at 7800rpm so they will be fine Mark.
Anything heavier and your just wearing away your cam and lifters for no reason, CVH heads have a very heavy valve train and poor lubrication so it's not good at the best of times lol