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Discussion and questions related to the course Engine Building Fundamentals
I'm in the process of rebuilding a 1.8T 20 valve VAG engine. I'll be using a set of second hand cams which have been polished, and a new set of hydraulic lifters to go with that.
I was wondering which kind of break-in process do you guys think it's safe to do? I've read engines with flat tappets cams must be revved to 2500rpm as soon as they are started and for 20 minutes to ensure the cams and lifters break-in properly. This however doesn't sound very good for the piston rings.
What do you guys usually do in those cases?
That recommendation is really for the flat tappet camshaft followers used on overhead valve (pushrod) engines where they rely on splash lubrication of the followers during that critical bedding in operation. Modern overhead camshaft engines usually have a pressurised oil feed to that highly loaded area, so it isn't needed. However it's still strongly recommended that liberal amounts of an anti-scuff lubricant be used - if you don't have some, I use a molybdenum (sp/) assembly paste or, as a compromise, a moly' grease.
That said, I'm a bit leery about using second hand camshafts with potentially unknown histories, especially if allegedly 'polished' as that removes material from the camshaft, inclusing some of the surface hardening, and/or treatment if used.