My watch said about 12 minutes, at somewhere around 2-2400rpm, then I dropped it down a little to about 1800. The cam is the XE268, or perhaps the 262, but in any case, it's not very large, and the spring pressure isn't very high. On heavier/racier stuff, I'll run them for a bit longer, with no inner spring. But using the electric fan and a lack of operating temp gage (factory intake.. I didnt have the right adaptor) made me nervous. So I shut it down. I think that's a prudent choice. We were very carfeul to only turn the engine over to pre-oil, and it fired off without turning over more than once I think. Aside from a couple minor issues, it went comparably easy. I'll have to hit the link from home to see it run.