Quote:
Originally Posted by Ultramaroon
More than materials and lube, the main advance in play here is the manufacturing process.
Break-in is to give the parts that aren't supposed to come into contact a chance to rub against each other and wear down until they don't. Not much need for that anymore, not unless the build was for shit in the first place.
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I believe it's still needed IOT ensure the ring and bore, ummm, leave a spot for the oil to sit on the surface of the bore to lubricate the ring and bore.
Other wise the hone gets screwed up and there is glazing on the bore, which will cause blow by.
It's more technical than my uneducated rambling though.
There's some good engine building sites that can relate it better, they even have pictures taken with microscopes that show the difference between what constitutes a good lubricated seal, and a poor one, and they explain how the different break in methods affect the bores.
The advancements in the honing methods now are also a good read and very enlightening.