.60 overbore on a 1968 340

5-360 casting date 6th January 1971

Already +0.040"

Sonic checked as follows (1 reading every 1/2", full height and all round each cylinder):

Min thickness found:
Major Thrust = 0.232"
Minor Thrust = 0.201"
Non Thrust = 0.177"

Thickest reading:
Major Thrust = 0.354"
Minor Thrust = 0.342"
Non Thrust = 0.303"

Fair bit of core shift. Now bored +0.070". Based on the above theory of maintaining at least 0.130" min all round (in this case on non thrust) this block would be good for 4.130" (I have no intention of going further than 4.070", the thicker the better)


Cheers
Jamie