a lot of these running in myths stem from the early days when machining wasn't as accurate etc, the main reason to run in a NEW car is to scrub the tyres and brakes, sod all to do with the engine IMO
Agreed but when most of us are building engines now who dont work for a manufacturer we are doing so with out of date equipment by comparison.
What do you use to rehone a bore after a rebuild with new rings for example? Personally I use a flexhone which is the best thing available to a home mechanic or small business IMHO, but its certainly not upto Honda standards, lol
various engine builders have different opinions, but mine is if somethng is going to go bang why delay it by 1000miles @ 4000rpm - it'll still go bang regardless!
This is true, if you have got something wrong in the build, you cant fix it by driving gentley, lol
Friend of mine had a cossie engine built by quite a well respected engine builder and was being told it was using oil (a LOT of oil too, like a litre in a 1000 miles of normal road use) because it wasnt yet run in properly, and he'd done 800 miles on it!
first start fine, high load low rpm until its hot, then gradually go more and more illegal
Agreed, start with lower rpm and build up, I think most of us agree on that, its just the rate of buildup that varies, I find the more engines I do the more I increase the rpm sooner TBH, and its yet to introduce a problem for me, but im still conservative compared to some.