If you use all the performance you will be getting, the revs will be high and so the bore wear rate will also be high. Then wnen a further re-bore is required is where the cost comes along. The 1380 will probably not take a further bore, so it will need to be sleeved back. but the gap between cylinders 1 & 2 will be very close, so it will not be a straightforward job. In fact, it will probably be better to get another block, thus scrapping another 1275 block. Remember, there will be no more new blocks made and another classic car engine will then be scrap.
The only reason for a 1380 is for motor-sport, where the regulations allow this size of engine in a Mini. For the road there is no advantage at all, but there are disadvantages.
Edited to add, You will be sprinting the car and will, therefore, have high engine wear. Best get a spare block ready for when you need it.
Edited by Cooperman, 13 October 2014 - 04:43 PM.
