if a 305 is the same block as a 350, and they have the same stroke, then the difference is the bore.
if a 350 can be safely bored 30 over, why cant a 305 be bored out to a 350?
its the same block. so it has the same space for the cylinders. why do people say that boring a 3.736 cylinder of a 305 out to 4.0 350 bore is wrong or bad? yes i know its about .25 more but its not like there is a different block used for the 350, or is it?
can you punch it out to the water jackets and sleeve it?
why have to buy a new block if we already have a 305 which is supposed to be the same block?
i am confused about this one. does anyone know?

 

They are different castings. 305 walls are not thick enough.

 

thanks for the reply, but what walls are you referring to?
the center point in the 305 cylinder is the same centerpoint in the 350 cylinder.
so what is not thick enough? there cant be a difference between the center points of the cylinders, so what is it that is different?
i know im a little slow on this one but the casting is the same, the water jackets are the same, everything that is part of the casting is the same.
are you saying that the cylinder sleeves are not thick enough? if that is the case you could actually bore the thing out as far as you want, and then put sleeves into it, or am i way off base here?

 

the 305 and 350 are different blocks that share similar parts. the 305 would have to be bored more than .250". it is commonly not recommended to bore more than .060". to answer the question, the main differences are on the inside of the blocks. adding sleeves is intended to provide a new surface for a cylinder that has been damaged.

 

i thought they were the same block but a different bore?
even the crank is the same, but weighted differently for the weight of the lighter 305 pistons vs the heavier 350 ones - or so i am told.
so how are the blocks different - other than bore? how do the walls of a 305 bore become thinner than the walls of a 350 bore, if they are the same casting?
its not like dr who, where things are bigger inside of the engine for a 350 than they are for a 305. they are the same size block.
they even have the same bolt points inside and out.
so im still confused.
can you be more specific?

 

You'd be correct if engine blocks were solid hunks of metal - but, they're not. They have internal passages for oil and coolant.

The cylinder walls are basically the same thickness, so they can't be bored more than .060 over. Since the outer dimensions are basically the same, that must mean either the coolant passages are larger or the thickness of the outside walls of the casting is greater.

Oh ... and they're not the same castings as proven by the various casting numbers.

 

there is light at the end of the tunel. thanks for clearing that up. question answered.