[patkeefe]

Start up is start up. Start up adversely affects everything. Warm or cold, there is no oil pressure. (I have to reach back in my feeble mind to fluid mechanics). I think there exist at least three states of lubrication; boundary, mixed-film and hydrodynamic. When you start up the engine, every moving part depends on boundary lubrication, the layer of lubricant residually "stuck" to the moving and mating part surfaces. Once we get oil pressure, we are in the other phases of lubrication, which are more protective of the moving parts. The simple reliance of boundary lubrication for the time period between cranking and having oil pressure in the galleys feeding the moving parts is what causes wear. This wear is on everything; guides, crank journals, cams, everything.

Ever see a commercial where the product shiller will show an engine which has just run 10,000 miles without ever shutting off (I think the old STP commercials), and they show the lack of wear which they attribute to their product? There is no wear, because they only started it once. Once you have hydrodynamic pressure, you are golden!

If you rig an Accusump to your engine, you get 15 seconds of oil pressure in the galleys...hydrodynamic pressure at start up, or mixed-film at worst. You remove the reliance on boundary lubrication, and remove the wear. Following up on your rigorous treatment of clearances, you get a tiny amount of wear PER START UP. Multiply this times (maybe) six starts per day of car use times five days (we all use our 911's for work) for five years...it becomes a big number. How long to get to the wear limit? Are guides more worn than, say, a rod journal? (Engine rebuilders can chime in here) My experience is that exhaust guides suffer at leat twice the wear of intakes due to the heating effects
Pat