4.040". The standard bore is 4.00".
Chevy 350 engines are bored to a 4 inch bore.
a Chevy 350 bored .060 over would be 360.4 cubic inches
4.030"
A 350 starts out with a 4.000" bore and a 3.48" crankshaft stroke which really only gives you 349.8 cubic inches. (Chevy rounded it up to 350) Your engine which has the same stroke of 3.48 but now is bored .030" over (making the cylinder bored size now 4.030) total size of 355.1 cubic inches or just a 355.
Its a 355 cubic inch
Most builders feel it shouldn't be bored over 4.065".
355
Take off a cylinder head and measure the diameter of the bore.
Typically if the motor has been bored the top of the replacement pistons will have it stamped on top of them. for example if bored 0.30 over this will be on the top of the pistons.
It will be close to 315 ci.keep in mind that a 350 is not really 350 but 349.xx or look at this way, for every 030 over in bore = 5 ci.
A typical bore size for a Chevy 350 engine is 4.000 inches. A bore measurement of "sixty over" indicates that the bore has been increased by 0.060 inches, resulting in a final bore size of 4.060 inches. This modification is common in engine rebuilds to increase displacement and improve performance.