So i am looking for some guidance on injector sizing for here in CO (5k feet).

My set up is a stockish B16a (built head, stock cams) with a GT3251B turbo and i am looking to be around 300whp. Any suggestion on injector size that I should start at considering altitude? Fuel pump is an inline walbro 255.

let me know if any other info is needed.

 

The corrected altitude where I am at is often above 5000ft. I am around 300whp and went with Injector Dynamics 1000 cc injectors. They idle better than stock and give lots of room to grow. I am at 50% duty cycle @ WOT.

 

humm...I was thinking something closer to 650cc

 

just go with id1000, like he said you should be able to get it to idle fine and have injector left.

 

Remember, there is a difference between the flow pattern of a Bosch-style injector vs the standard Rochester/Lucas (RC) injector that you're thinking. It may be much larger, but the characteristics seem to be that much more usable than the Rochester / Lucas version.

For your application, I'd use a Bosch-Style 750cc.