Injectors
There is a lot of good info, excellent helpful members plus a clueless ignoramus or two that provide unintended comedy occasionally at LS1TECH
Normally, I ask a sponsor after all of the engine parts are selected. It's easier to estimate the required injector size later in the build rather that earlier. I look at the total airflow the cylinder head is capable moving and power adders if any. From the pictures it looks like you've set up an NX system. How much NOS/spray do you plan to use?
In my experience, usually engine builds or engine updates go best when it is all planned around the cylinder heads being used, the application, intended power band and rpm. The quality of fuel octane helps determine how much compression and suggests what pistons to consider with the supporting bottom end. Those choices tend to suggest the intake and throttle body needed for the application. Next comes picking the cam and planning a valve train.
The Kelford cam listed is a 230/236 .600 lift on a 112 LSA. Appears similar to a Hawk's Motorsports Sinister 231/236 112 cam that typically makes 450-470 whp with ported PRC 5.3 heads, FAST LSXR and 102 TB with #42 pound injectors.
Depending on how much NOS and how much RPM, my guess is at least a #42 pound injectors or 450cc to a #62 pound injectors or 650cc injector. As Darth mention Lance of Pantera EFI would be an excellent person to talk too.
Ideally, one wants to run the smallest injector that supports the power level at 80-85% duty cycle. Smaller injectors are usually easier to tweak when tuning and tend to give better drive ability.
Best regards
