I was wondering what i should bire my gsr to. I am going to sleeve the block also. I want something reliable and can produce good power. Looking for 500 to 600hp. I will also be using a stock gsr head. Thanks in advance for any info.

 

I believe 81-84mm can produce that power. I think the bigger bore can create more tq

 

Only if you have the stroke with that bore. Bore alone typically only does 20ft/lbs max from what I've sen on B/H/K series over the years. All depends upon what you want to do

 

alright here is my opinion from personal experience.

i would go with 83mm. its a nice compromise between the smaller 81mm and the larger 85 which i think is about as high as people go on boost. this will allow for a few times you can overbore should something happen or whatever and still have a usable block.

this is coming from a guy who started at 84mm, fast foward a few years, a .020 over from ptw contact and a few hones on top of that im looking at 85mm next and the probable limit of my block in a boost motor

 

I found 84mm to be a bit better from a replacement parts standpoint. Even if you don't get the "GE Prepped" Headgasket, there's nothing like using OEM time and time again without having to wait as to whether or not GE had "another batch" of 83mm completed. A few of those I know personally that run 83mm have about 3-4 headgaskets in their storage just in case something goes wrong, their not waiting for weeks to get replacements.

I too come from an 84mm world, and perhaps I'm just that lucky bastard who didn't have to sweat going 85mm, and *knock on wood* nothing yet will happen.

The difference in torque between 83mm and 84mm is negligible at best.

 

Thank you for input, im going to do 81.5mm since anymore really isnt going to get me much more power plus easier to get headgasket since i can use oem.