K20a engine build

Hi guys. I’m in the process of building a k20a engine. Right now it’s at the machine shop and my next step is to figure out cams, pistons and rods stock compression is 11.5-1. What should I lower it to. It will be turbo charged. I’d like to stay under 20psi of boost. Goal is 500hp street car on 91 octane. sucks I can’t get e85 in Canada.

thanks for the guidance.

sorry if it’s posted in the wrong spot.

Comments and discussion points, rather than specific advice -

Depending on exactly where you are, you should be able to get 93, or even 94 PON fuel, it's be worth checking out your local service stations' parent sites as many will list where the higher octane fuels are sold. For example - https://www.petro-canada.ca/en/personal/gas-station-locations?amp;fuel=Ultra94&latlng=51.032362,-114.064579&zoom=12&place=calgary&fuel=Ultra94

Engine capacity helps, and as you're not that far off looking at sleeves, and you're needing pistons anyway, you may find it relatively easy to use a big bore kit. Either way, you're probably looking at around the 9 or 9.5":1 CR. The guys that sell this stuff are generally very experienced with the engine, and should be able to advise you what should work best with the fuel available to you.

Keeping the charge as cool as practical will increase the charge density and reduce the detonation, or pre-ignition, potential, so a good charge cooler should be high on the parts list.

As power is a function of torque (bang/boost) and rpm, if you're limited on the former you may need to wind the engine out a bit more.