426ci

There's two ways for getting 426". One is the 4.18 stroke crank, one is over-size boring. IMo, there is no reason to over bore to reach it unless the block has an issue and for some reason sleeving is out. The longer stroke will lower the peak rpms and flatten the curves for most builds. The longer stroke needs I beam rods I think. Personally I've never done one so I can't comment too much really. There's less than 5% difference in the strokes from 4 to 4.18 and the pistons and maybe rods would be more expensive. I think if it were me I would either go the usual 4" combo or recommend stepping up to the 4.25 stroke and a new block and go bigger. I'd rather spend less to get similar results or spend more to get a better result. You figure 3.31 to 4" is 17% or so more stroke, and 3.31 to 4.18 is about 20%, 3.31 to 4.25 is 22%. The costs for those increases goes up a lot faster once you get past 4" stroke due to airflow depands and parts sourcing. Just my opoinions tho.