okay search does not really help for my aplication and i respect the guys in this section to answer nonbias and have helpful info.

i have a ls2 bare block that will be built with a 4.0 stroke and 14:1 compression. it will have a big solid roller cam, afr 225 or tfs 215 heads with victor jr intake. it will be setup for a 2 stage 300 shot. looking to get close to 900rwhp.

i know it is going to be really expensive but was wondering if i should leave the 4.005 bore or go with a bigger bore. just curious how much more power will a 4.125 bore make in my application and how does the bigger bore affect the life of the motor. it is by no means a daily driver and will only see 110 or higher leaded gas.

 

Well the larger bore will really shine on high flow heads. It will help unshroud the valves and the potential to make more power goes up.
A lot of companies advertise their flow ratings on heads with a 4.125" bore.
If it is a max effort engine the bigger bore could be worth the expense.

 

Probably not worth it if you're going to run 225/215cc heads, unless the valves are larger than 2.08". Gains will probably not be worth the time/money/hassle of sleeveing the LS2. If you still need more power, put in bigger jets.