Better to bore the block or not?

[4eftePaseo]

hey i was just wondering if its better to bore the block out when putting new pistons in... as in going with oversize ones, lets say like 74.5 or 75.5. What are the disadvantages of not boring it out (with 74mm pistons) and whats the difference between the 74.5 and 75.5 (besides obviously the 1mm )

 

[Aga]

boring will ensure a better fit for the piston (not to mention it is needed in case of oversize) due to wear on the cylinder walls...they tend to become oval with maaany kms. 74.5 is the usual oversized piston, some fearless blokes go for 75, though that makes the cylinder wall between cylinders too thin... ive never heard of anyone going for 75,5 i dont think they even exist...

 

[speedvision]

as aga said boring will be better...gives u better piston fit and fresh engine

the guys in denmark run 75.5mm

sam