Why are over bore sizes measured in thou's instead hundredths. ie 0.004 of an inch instead of 0.0040
Bore Sizes
Started by
HUBBA.HUBBA
, May 26 2018 09:39 AM
1 reply to this topic
#1
HUBBA.HUBBA
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Posted 26 May 2018 - 09:39 AM
#2
Spider
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Posted 26 May 2018 - 09:56 AM
Typical Overbore sizes are 0.020, 0.040 etc so that's 20 and 40 thousands. It's expressed this way as many measurements in the engine at in thousands and not 100ths or 10ths. The other reason is they are not always to whole numbers like these, eg, there's a few I've done at 0.093" and 0.114".
These are only 'nominal' sizes and not exact, it's only to give an indication of which over bore the block is on (ie std, 1st or 2nd etc).
The exact size is worked out off the pistons that are actually to be used.
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