Roller LA Deck Height

AJ/FormS said
At 5500ft, I seriously doubt that excess compression is gonna be your problem.
Scr is nothing but a tool to be used to achieve a certain pressure. A pressure known to to do what you want it to do.
Choose your cam first,calculate the Ica off the advertised duration, and plug your numbers into the Wallace calculator, and then work backwards. to your desired pressure/available fuel target.
For instance; your 360 at 5500, with a 340-type cam, will need 10.8 to achieve 155psi to run 87 with that .040 or less Q, in iron.. On 91 you can run it up to 11.0 or perhaps a lil higher.
Whereas, at 9.5 it will be a bit of a dog until around 3500 rpm.
With alloy heads, 180/185 is possible still on 87, and that might like an Scr of over 11.5
Now you got a ripper of an engine below 3500, but then you might run into a different problem, hi-speed detonation.
That 5500 ft is worth about a full Scr point over 1000ft. In other words a combo that runs nice at 9.8 at 1000, will need 10.8 at 5500.

I had some time this morning and played with dynamic compression and cranking pressure calculations. The cam I'd like to run in this motor (Lunati 20200711, advertised duration 270deg with a 106IC) should put me at 8.73DCR and 154PSI cranking pressure, assuming a 5cc Piston relief (KB107), 64cc head (nominal for EQ Mag, need to measure), and +.030 pistons set to a .040" quench. That sounds pretty solid for a street motor, and should get by on the 85-86 octane regular grade we have around here. I can always step up to a mid-grade gas if necessary, but running the cheap stuff for a daily is appealing to me. That would leave Premium fuel on the table if I need to venture to a lower altitude. I also run a GM HEI 5 pin ignition module that allows 5 degrees of timing retard when the 5th pin is grounded. I could get creative with that and a hobbs switch if I run into issues on the edge. Dehorning/polishing the combustion chambers and valve reliefs might help a little also.

Stepping up to a piston like the Icon742, with 9.6cc relief, would drop DCR to 8.3, and cranking PSI to 143. That would provide more margin for 85 octane, but is also leaving some performance on the table, especially as I travel up in altitude above 5500.