well i was reading a mini mag and it had a car with a 1380 and the reporter said that block being bored to 1380 bought the block to be closer to squarer giving a smoother idle
IS this fact less meet in between the cylinders the smoother the idle

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Sounds like BS to me...
Whether it idles smooth or not depends on many things, but boring it to +.115" isn't one of them, IMO.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

yeah i thought so i know there are a number of variables which need to come together to give an engine a smooth idle but was just wondering if boring the block was one

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Guys it is not the bore size alone that makes the difference but it is in fact the capacity of the cylinder, whether it is bored or stroked. The increased capacity of the cylinder changes the rate at which air is drawn past the valves due to the expanding chamber's negative pressure. Conversely you can run a cam with larger overlap and greater lift to take advantage of the the greater vacuum phenomenon, and there is proportionately less residual gas in the chamber, giving less of an affect on idle. This is one of the reasons why large cc engines can sometimes (and I mean sometimes because of all the other variables) run with a smoother idle on the same given cam.

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1970 Cooper S ex-Bathurst & ATCC
1964 Austin Cooper S ex-Group C race car
1967 Morris Cooper S ex-Group B
1962 Mini Speed sports sedan
1968-71 ex-Peter Manton Shell car

ahh ok thanks for that now i understand what he meant

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