The 302 has extended cylinder skirts for the longer stroke and to improve stability and reduce piston slap according to my ford interchange manual. I have never measured this though. I think most engine builders prefer to build 331s as there is less load on the rods for some reason.

 

a 289 block can be used in a 347 and a lot fo the problems with the 347 has been worked out over the last few years. but like Silver Ponys said the 331 has less rod angle and there for puts much less stress on the mains in the block you can actualy make more hp with the 331 than a 347 you just have to build a little more radical engine to do it.

 

i may end up doing a 331 if it will be more reliable....i don't have to squeeze out every cube that i can , as this is a street driven car and will rarely, if ever, race.

It will also have to run on 91 octane...race fuel costs way too much for a car that does 6,000 miles a year [sm=jawdrop.gif]

I just want to make a step up from the 289 when the time comes to rebuild

 

302 block had extended cylinder wall skirts to compensate for the longer stroke. Thats what made a 302 a 302, the 289 and 302 had the same size bores

 

it wouldn't be that hard to find a 302 block to build a 347 if you wanted they are still pretty cheap.

just keep the compression about 10 to 10.5:1 and you will be able to get away with premium pump gas. with the right heads and cam you can make a lot of power out of a 331 at 10:1 compression.