so after getting my truck back together, I ran it for less than an hour and the oil pump is toast as is the rotating assy. I have to rebuild it and machine the block. The question is how big a displacement motor will the stock injectors support? I have heard of 383's with mild cams on stock injectors. I cant confirm them though. Anyone know how big before they just dont flow enough fuel?
Injectors, especially the poppet ones, are interesting things. ideally what you want is to shoot for having the injector be cycling at no more than 80% duty cycle (abr. DC) at its peak. this is because at higher duty cycles the injectors don't have enough time to close before they're commanded open again. this is bad because when these high duty cycles get reached, all linearity and predictability of the injectors go out the window and you could end up with unpredictable conditions in each cylinder, overly lean in one, overly rich in the next, whatever, even tiny untestable differences between injectors could translate to huge differences at high DC's. this is true for EVERY fuel injector, TBI, real MPFI, Poppets, everything. for regular injectors (i.e. not poppet ones), the injectors go static around 91-93% DC. (static means that they are wide open all the time) I don't know the specs for a fully static poppet, so I use 100% DC for static calculations with the poppets.
now the poppet style injectors are even more unpredictable because the metering body is in a central location and the injector tip (the poppet part) is pressure controlled to open when the fuel hits it at a high enough pressure. the actual flow of the poppets from the factory can also vary a decent amount. most are about 19# (this is at the testing pressure of 43.5psi or 3 bar), and on our fuel systems (58psi), they run closer to 21.9#, however I have seen some stock ones tested that flow closer to 26# when static at 4 bar (58psi). so the cacluations for how much power they can support can vary a bit depending on how much your specific injectors happen to flow.
so with the caclulations that all your injectors flow the stock specs of 21.9# at 4bar fuel pressure. with the 80% duty cycle peak they could support ~280 hp, now if you let them go all the way to static (which isn't recommended or ideal) theoretically they could support about ~350 hp. now you'll get people who can run more and less than these numbers on the poppets simply because of the variability of their flow from the factory. the most I've ever seen someone get is a guy on FSC named 'vortec stroker' who has alot of mods and has dyno'd 330 RWHP on the stock poppets, which is around 400 FWHP. now I guarantee you that his injectors are going static (which isn't ideal), and he must have won the poppet lottery and just happened to have alot of the stock poppets that flow more than 21.9psi (in fact, for those #'s I calculate them out to be flowing around 25#), so although his performance with them is impressive, I wouldn't count on most others to handle that amount of power.
so to answer your question, on a 383 with a mild cam, you'd probably be reaching the limit of the injectors but still okay.
