What is Necessary Octane for 12:1cr?

[DREGSZ]

Hi All, I know this isn't a Forced induction Question, but ya'll on this forum are quick and sharp. What is the correct octane needed for a 12:1 race motor, solid flat tappet, with 750 carb, run at sea level? I just put in 110 leaded because it all costs the same at the track, but what is the minimum Octane that should go in this motor/ THanks Evan

[Rkreigh]

110 should be enough. need info on what heads, cam, rear gears, ect...

all those variables affect what octane the car will need. more octane than needed will lighten your wallet but not make more power.

with a carb, as with efi, you need to have the a/f and timing right on to run big compression. chamber shape, quench, alot of things impact what octane will be need to make max power.

sounds like a fun ride. :jester

[ANTI VENOM]

Yes, we need lots of detail as stated above. I figured I could run 12:1 with fuel injection on an LT1 with the right cam on pump fuel. Anyway, cam, and rod length play apart, so give up the details.

[Brand-X]

ditto above...cam will determine dynamic cr.

[DREGSZ]

Hi All,
Sorry to keep you waiting on the vitals.

I run 110 because it is there at the same price, but I just found a cheaper source for 100 octane so I'm trying to find out what is the minimum I need, in case I can get by with less then 110.

The cam is a flat tappet, solid lifter Crower Circle track cam. PN 0350. I'd have to check the Cam Card to find out the lift.

I have Prolightning 220 heads with custom CNC 66cc chambers.
6.2" rods, big valves, 1.5 Rockers

Let me check what other info was needed

[1996man]

ttt :lurk:

[ANTI VENOM]

check the cam card and tell us what the LSA is and the duration at .050 for in/ex. That will get us started. I would fill it up with that 100 octane and see if you get any detonation. If you do, have a can of 104+ to throw in. That will tell you if you can get away with 100. Just a though.