Jeep Strokers

Well after 3 junk heads from Clearwater I gave up and took one in to a local machine shop, they decked it flat but had to remove a lot of material.
Before I was measuring 57ish cc chamber vol. now I'm measuring 53cc.
This bumps my SCR DCR up from 9.3 SCR and 8.0 DCR to 9.68 SCR and 8.3 DCR, my quench is good at under 0.044" but I was hoping to run 89 oct.
Has anyone had experience running similar numbers? What octane do you think this would need to run without ping?
Really hoping its no more then 91 oct required.
Apologies if this kind of thing gets asked a lot, I'm learning as I go on this build

Extra info if needed:
4.6L disp.
7120 iron head
Russ autotec pistons: 3.905" bore, 1.385" comp. dist.
Scat rods: 6.125" length
Eagle crank: 3.895" stroke
Pistons sit above deck by 0.0065" so -0.0065" on the calc
H.G: felpro 530SD, 4" bore, 0.050" thick
Comp 68-232-4 cam

-26cc dish on the pistons

I also have your SCR at 9.68:1.
You might just get away with 91 octane given the tightish 0.044" quench. If you polish the combustion chambers and the piston dishes to a near mirror like finish, you'll be fine.

Thank you for the reply Cheromaniac
The pistons from Russ are nice and smooth and shiny with some light marks from milling the dishes.
The bowls on my 7120 head still have the casting texture.
I'm measuring chamber vol. using plexiglass + dropper, getting 53 maaaaybe 53.5 cc or somewhere in between.
If I could just add 2cc my numbers look much better.
I do have extra valves I could sacrifice and a die grinder, but I'm not too comfortable with making changes in the chambers unadvised.
Any tips or suggestions would be appreciated.

Heres what the chambers look like.

Z2DoorXJZ wrote: ↑June 8th, 2025, 4:22 pm I do have extra valves I could sacrifice and a die grinder, but I'm not too comfortable with making changes in the chambers unadvised.
Any tips or suggestions would be appreciated.

Just smooth away the rough casting and any sharp edges in the chambers.

Here is what I did, to give you some ideas.