I want to use a sleeved GSR block bored to 84mm, LS 89mm crank and the RS Machines ITR style pistons to get to 2 liters. If I use the LS rods, the Zeal Auto Werks (http://www.zealautowerks.com/bseries.html) tool says I'll get like 12.5:1 compression using the GSR head without any milling. I used the standard ITR pistons to calculate compression though. RS Machines doesn't list their compression height or dome volume.

***How can I drop my compression down to around 11.5:1 without using different pistons, or is 12.5:1 acceptable for a daily driver that will run on 91 octane gas? I know I can run colder heat range plugs and retard timing. If that's too high, what other options do I have? Can pistons have the dome milled down, what options do I have for custom rods...?

Also, I'm concerned with the fact that the head came off a 81mm bore engine and the block will be 84. Wouldn't there be a ridge on the head that doesn't match up with the cylinder? I couldn't find a schematic of a GSR head to check or see if it could be milled out and what effect that would have on compression.

 

Ok, I found SuperTech pistons in 84mm diameter and 1.4cc dome. Thank you everyone for the help.

Does anyone know how much a block gets decked during rebuild when it's sleeved?

 

I dont think your cr will be as high as you think with the RS pistons.
More like 11.7-1 range.

Heres a link to the thread for the RS ITR Piston specs here

Also fyi a good way to bring down compresion is with a thicker h/g like ones from cometic, even
though I think with those pistons and using the gsr head will be perfectly streetable.