[jpnovak]

I have finally collected all the necessary parts (sans cams) to build a 2.5SS for my 71 targa.

Build will be based on a 2.7 74 7R case with the usual updates
90mm Nikasil cylinders
90mm JE pistons (10.5:1 on 70.4 crank)
66mm non-coutnerweighted crank that will be cross drilled (modified bearing included)
DC-30 Mod-Solex cam

The engine is designed to replace my 2.2E. I love the engine, it has a perfect power band yet needs just a little bit more. More torque in the power band (displacement increase_) and more top-end (cam choice). I want to maintain or increase how fast it spools. Ultimate HP is not my goal. Highly responsive backroad/street engine is my goal. Here is my question.

The pistons should CC about 9.9:1 on the short crank. I have not measured these out since I have not built out the case. I can use a late 2.7 head with slightly more dome volume (plug hole relief) to drop this slightly. Does anyone have real world numbers for such a combination?

Is nominally 10:1 acceptable on a 90mm bore with single plug? (consider 93 gas for your thought process) I do not mind twin plug and have built a few in the past. I just think this might be added expense I might not need.

I realize that twin plug will help the motor in many ways. Just wanted to hear thoughts on the CR.