From:
http://www.geocities.com/lutransys/jlucius2/j2-2-pistonguide.htm
"A question often asked when rebuilding an engine is "How much can I overbore the cylinders?". From the service manual engine cross sections I guessed that the cylinder wall thickness might be 0.25". Joe Gonsowski (3SI Message Board) had his block sonic tested (top, middle, and bottom of bore) during his rebuild. Average wall thickness was 0.288" with a minimum value of 0.231. The stock bore is 91.1 mm (3.5866"). I had my engine bored 0.050" over stock (92.38 mm bore for a displacement increase of 84 cc) which reduced average wall thickness to about 0.235". After only a few thousand miles I have not yet encountered any problems, but the increase in wall deflection and stress may reduce the durability of the engine somewhat. Some of our cast-iron block 6G72 engines have been bored 0.075" over stock (a 93 mm bore, increasing displacement by 128 cc) bringing total displacement to 3100 cc and average wall thickness to near 0.200". I have not heard of 6G72 engines with larger bores than 93 mm. "
.jon
http://www.geocities.com/lutransys/jlucius2/j2-2-pistonguide.htm
"A question often asked when rebuilding an engine is "How much can I overbore the cylinders?". From the service manual engine cross sections I guessed that the cylinder wall thickness might be 0.25". Joe Gonsowski (3SI Message Board) had his block sonic tested (top, middle, and bottom of bore) during his rebuild. Average wall thickness was 0.288" with a minimum value of 0.231. The stock bore is 91.1 mm (3.5866"). I had my engine bored 0.050" over stock (92.38 mm bore for a displacement increase of 84 cc) which reduced average wall thickness to about 0.235". After only a few thousand miles I have not yet encountered any problems, but the increase in wall deflection and stress may reduce the durability of the engine somewhat. Some of our cast-iron block 6G72 engines have been bored 0.075" over stock (a 93 mm bore, increasing displacement by 128 cc) bringing total displacement to 3100 cc and average wall thickness to near 0.200". I have not heard of 6G72 engines with larger bores than 93 mm. "
.jon
