This is from a Lotus site, the poster is a compatition engine builder.
Quote
I would not draw any conclusions until the rings have been bedded in under load. This should be done immediately if you have not done it already as running a new engine under no load for extended periods can lead to the bores glazing and the rings never bedding in.
To briefly repeat the running in process I use.
1. Use a specific running in oil that will have high zddp levels or any cheap mineral oil with a zddp additive
2. Start and warm up the engine and check for leaks and noises and setup the carbs . Dont run it for more than 20 to 30 minutes and dont let it idle for to long during this period
3. Take the car on a quiet road with no traffic and an appropriate speed limit and do third gear acceleration cycles at full throttle from approx 2500 rpm to 5000 rpm and then slow down again and repeat. Do this 40 or 50 times over maybe 100 km's. This will fully bed in the rings
4. Change the oil to the long term oil your going to use and filter and your done ( assuming the engine was built right in the first place with correct tolerances and machining / honing of the bores etc)
Un-Quote
The not let it idle is for the benefit of cams and cam followers.
Jon the Chieft
