1.7rr'
#4
On a lazy lobe cam like the 306 it will be ok if you have the springs to handle it, but on a more aggressive cam like an XFI specced for 1.6s you will have a hell of a time controlling the valves.
#9
I had a LE4 383 grind with barely 500 miles on it that I sold since Llyod told me it would be hell to control with my 1.7 shaftmounts no matter what springs and retainers I run. The extra ratio does not just increase the relative duration and lift, but it makes everything happen quicker. Add that to aggressive lobes and you have a recipe for a very unruly valvetrain that will be a pain in the *** to control at high rpms.
In your case, you would need higher end, more expensive springs and retainers to run them with the 306(which isn't the best choice anyway), and it would not be worth all the extra money.
Install the 1.6s and be done with it .