My 1990 7up model has a gt40 crate engine w/ aluminum heads, e303 cam, cobra intakes, 65 mm throttle body, 76mm C&L maf, 255 fuel pump, adj regulator, and ceramic coated shorty headers. Do I need to move up to 24# inj or can I stay stock?
I would say if the car is running well you could well move up to a larger maf and keep the 19's..or if future upgrades like a head upgrade I would look to jump to the larger injectors and maf.
it can run fine with 19# but i would go ahead and put 24# in. if you went with a larger throttle body i would say go 30#. but always remember that you will be able to adjust the pressure of your fuel and when you need the bigger injectors and dont have them you'll be singing a different tune.
30lbers are definately not needed. I have them and they are to big for a bit more aggressive setup. I wish I would have went with 24's.
24's would be a more ideal setup if you can swing the price and maf calibration. 19's will work though.
hessian - A throttle body isn't going to do anything significant enough at all to warrant an injector change of 6lbs. That is roughly a 20% injector lb per hour change just buy adding a couple hp. Not needed for sure
24's, so you have room to upgrade. 30's prolly wont be needed unless you stroke it(which i assume you wont since you just bought a new shortblock) or if you add boost, in which case you'll need even more fuel.
Maybe this will help you! http://www.injector.com/
Look under injector selection guide. If you know the hp of your motor, this can help make your decision.