I have an 85mm GE sleeved LS block that needs a rebore and hone after some significant scoring to the cylinder walls.

When the engine was last in service it was 11.4:1 CR, stroked to 95mm, and fed by RM m24x cams. The motor ingested a throttle butterfly bolt and did a diddy on my #2 cylinder, so I never had time to dyno for numbers. My only reference for power was that I matched run of the mill Stg 2 STIs.

On my rebuild, I have been considering moving over to the darkside with boost, but I had a question and a conern.

1. If I were to drop my CR to say 9.0-9.5:1, what kind of power loss would I be looking at compared to being 11.4:1? ~5-10% whp (about 10-20whp), less, or more?

2. Does anybody have any idea how much farther out I can punch these cylinders? The only number that comes to mind is 86.5mm at the max, but I think I could get away with 85.5-86mm to get rid of the scoring. Any experience with these sleeves is greatly appreciated.

 

I think your HP loss estimates sound fairly accurate.Youre probably gonna see a loss throughout the whole powerband dropping to ~ 9:1 with no other changes.

If you decide to stay NA, Ive seen a few b series builds around HT running 86mm bores, so I think you still have at least 1 more rebuild as long as the cylinders arent really messed up.
Going to the darkside might make HG issues even worse since it will be producing even higher cylinder pressures than NA. If it were me, Id take it to your machinist and have him bore to 85.5mm to see if things clean up first. You may have a "race only" block if it needs to go any more. If you want some additional insurance, you could always have the block o-ringed. I think you can have the head o-ringed instead, but Im not sure...
What kinda throttle body did you have if you dont mind me asking? You can pm me if you like.

 

If you wanna go "to the dark side", I dont know why its called that, anyways I would bore it THE LEAST amount possible to clean up the cylinder walls. You can run a 10:1 CR piston with boost, an it will still serve a DECENT purpose for NA. No it will not be as significant as 11.4:1, But it will still perform well.
As a side note a local shop in my area has their drag car on 35+psi making 1100+whp with 10.8:1 pistons. Ultimately its your decision.

 

I used to hear this term back in the day. People that go to the darkside (turbo) usually never come back. They get a taste for boost and theyre hooked. Before good tuning solutions were readily available (VAFC and FMU days), people would blow their engines left and right. I think the NA guys at the time gave it this name cause it seemed "evil" and was the cause of numerous dead hondas! haha
Boost is like crack. Once you get a taste, your gonna want more. I still am scared of the darkside! Much safer here on the brightside!

 

I am a Boost addict, I admit it. I boosted a stock GSR and it was like ecstacy. Once im done with school I will finish my 600+whp build on a precision 6262. BUT in the same aspect I am an NA guy. Hands down the most reliable and consistent power available. I am a V8 NA guy though (see sig) and making an easy 500+whp NA on a V8 for 3k is 100 times better then a 3k block for the same amount of power in a honda boosted that will run $5k+ and more then likely have issues after every weekend. My chevelle has NEVER been torn apart, modified or broke down. Been together 9 years and MANY redline runs.

OP take that for what its worth. I have been on all sides of the aspects and a honda+turbo is unlike anything else on the road.

 

Thanks for the helpful words. The SC6262 is what I am planning to slap on the from of my 2.2L B. I had a WRX with an STI turbo that I absolutely loved, but now I drive a European-only 321hp E36 M3, and that is NA and a LOT faster than my Subie ever was. I am a fan of both. I am afraid of building this motor the way to its full potential to see heartbreak again.
I am also in a moral conundrum whether to buy a set of pistons sized to what I believe is safe, and then bring them to the machine shop, or try to low ball it and have to do the whole porcess over again. I believe I will settle at 10:1. My V8 buddies tell me I'm out of my mind, but my last engine builder pushed me towards it. Either way I want a quick NA car, or a 500whp SC6262'ed B22, lol.

Pyro, you have PM...