Most modern automotive engines now use Moly top rings, where aircraft engines typically use a Chrome ring on a steel cylinder, or an iron ring on a Chrome cylinder. If you have your cylinders Nickel plated, then you can run a Moly top ring and skip the cylinder "break-in."
While people seem to get most exorcised about breaking in the rings, it's actually the camshaft that is the bigger concern, especially on a VW. On initial startup of a new engine, the camshaft usually doesn't get sufficient oiling during the first several minutes of operation if the engine is allowed to idle, which is the critical period for the cam and cam followers to wear in to each other. If you search on cam break-in, you'll find lots of information about running the camshaft at various RPMs for 20 - 30 minutes to break it in. While assembling an engine, the cam and cam followers should always be lubricated with a black moly based grease to facilitate initial cam break-in when the cam will be run with either new or freshly ground or overhauled cam followers. As for ring break-in, the idea is to create as much cylinder pressure as possible under the best cooling conditions you can provide during the initial break-in period. That presses the rings tighter into the cylinder walls to get a better seat. People go crazy over getting them into the air as soon as possible and run full throttle for the first couple of hours. I have seen folks run them full throttle for at least 10 hours! While that does insure a good break in, it's not necessary to treat the engine that harshly. While I was living in NM, I was based above 7000'. I did a fair number of top and major overhauls, all of which were broke in without ever exceeding 70% power, as that's all one can pull at that altitude. Those engines all broke in just fine. Personally, I never worried about break-in other than not spending a lot of time idling a new engine. I did my break-ins using Phillips X/C 20-50 AD oil, and recommended the same for my overhauls. In other words, I used the same oil as the engines always used, and operated them normally. Just don't use synthetic oils during the first 25 hours. The only significant deviation was to ensure the new engine didn't sit and idle until it had completed a couple of hours of operation. I found that iron rings on Chrome cylinders were the most difficult to get to seat. I also found that aggressive honing with a high pressure carbide cutting hone did wonders to aid with cylinder break-in, including honing chrome cylinders. Bottle brush hones tend to be close to useless and don't cut deep enough to facilitate good ring seating when used on a Chrome or nitrided cylinder. They may work fine on iron or unnitrided steel bored, but don't use them on a hardened bore. It seemed like used cylinders typically had 90% of the break in done in about 2 hours, while new cylinders usually took closer to 10 hours to seat in properly. -Jeff Scott North AR > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > Why do we "break in the rings" on an aircraft engine and not on our > automobiles, trucks, tractors, lawn mowers, outboard motors, etc.? Just > wondering.............. > > When you buy a new car your just go out and drive it home. On my new > mower last week I just started it and mowed the lawn. What am I missing? > > Larry Flesner _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
