I probly shouldn't have said overbored 6.9 not like they just bored them out to 7.3 but as long as the owner kept up with the additive to the cooling system them cavitation was kept to a min. the problem is the additives wern't always kept up with.

 

Actually the 7.3L is pretty much a bored over 6.9L, same crank and the rods are the same length. Compression ratio is slightly lower in the 7.3L Cavitation is more of a problems with the 7.3L.. but doesn't mean it dosn't occur in the 6.9L occaisionally too.

I think I am going to buy that 6.9L though. I haven't seen it in person yet but he is telling me the reason that his mechanic told him it has a blown head gasket is when he opens the oil fill tube it has drops of water on the cap and he can see vapor coming out when it is running... he tells me the oil looks black... not coffee colored or anything of the sort.

 

I did some checking and you are right the 6.9L has a bore of 101.6 mm and the 7.3L bore is 104.4 mm. The difference is only 3.8 mm or approx .1 inch. the stroke for each engine is 106.1 mm.

This is the result of a very common practice in engine making using a common block for different displacement engines. I suspect the international T466 also shares this block. Why re-engineer somthing that works.