Hoping Mike chimes in since he'll be doing the tuning....

I had simply planned to do bolt-ons to my n/a 5.4 Roush, but since my truck **** the bearings out I'm unfortunately going into the motor first. While its apart I'm gonna port the heads. If I can get the chambers opened up to around 48-50cc I can run a 4.6 Cobra piston and end up around 9.6-9.8:1 The question then becomes is 9.8:1 livable on 91 octane? Thats as high as I can get in the small town where I work, and where I fill up 90% of the time. If not, how high dare I go for compression?

edit: updated some information as I've found more...


Thanks for any input.

 

ttt for Mike....