A little knowledge can be dangerous and thats me at the moment.
I have a 40cc per chamber Pinto/Cortina Historic racing head.
On a 2.1 block the static compression ratio with a 1mm gasket is 11.2 to 1 far to much for even 97 RON but i have been reading about Dynamic compression ratio and with the RL22 cam that came with the head the dynamic compression ratio comes out at 9.9 to 1 with an inlet valve closing at 80 degs ABDC.
This could explain why the previous owner of the head could run it with a static of over 11 to 1 and not detonate.

Or am i missing something here.
I would hate to ruin the engine but its the difference between an Adjusa gasket at £37 or a Cometic at +£100

I have not see the calculation for dynamic ratio but I assume since it is associated with the inlet cam it must take into account the inlet valve closing point which is extremely crude.
What matters for knock is the conditions of the charge in the cylinder around TDC.
Yes the inlet valve closing point will make a difference but so will many other factors (air fuel ratio, chamber shape, tumble ratio, air temp, volumetric efficiency etc etc.)
If your engine ran successfully at 11.0:1 then the ignition timing will presumably be safe and so you can continue to do so.

Although if you do hear knock you will need to retard the ignition.

The point here is that i only have the head from the original engine and am building a block to fit.
The calculations on dynamic compression ratio are quite complex and take in to account the rod length, piston to deck height with the other factors used to calculate static compression ratios.
The stroke and rod length help to calculate how far up the bore the piston is as the valve closes for a given cam inlet timing, thus the dynamic compression ratio is found.
If you google Dynamic compression Ratio a load of American forums come up.
There pump gas is less than ours but also there measurement of RON is different so 87 American is i belive about 91 European
They talk about Dynamic Compression ratio of 8.5 to 1 on Pump gas and it is this figure i am trying to establish.
If i can get some opinions about this i will understand what Static compression ratio i should build for standard pump gas.

The problem with any of these calcs is that it they are too simple and just cannot account for the many other far more important factors.
The four stroke engine is very complicated and such a complex phenomenon as knock just cannot be accounted for with a spreadsheet approach.
If the calculation gives rule of thumb values which can be correlated successfully to engine data (Pinto), then use it.
Just my thoughts.

In very basic terms the higher the overlap and duration on the cam, the more CR you need to run to get the best out of it. The really powerful Pintos will probably be running more than 11.5:1.

Why not ring up Kent and ask what their recommendation is?