okay going to keep it short and sweet the motor is an lt1 355, forged pistons and rods, stock crank, heads are ported and polished with 2.02 intake and 1.56 exhaust valves, flow numbers are similiar to le2's, ported intake, cc503 cam, walbro 255, and going to get a pcmforless tune for now to get her running once i know what injectors i need. idk what im looking for cause all i keep reading is stuff that fuel pressures are different so it makes a 32lb injector act like a 36lb? idk really confused ans also the low and high impedence? if someone can give me part numbers to what i need or links please do thanks guys

 

The LT1 fuel system operates at 43.5psi. The LS1 system operates at 58psi. So if you try to use an LS1 injector in an LT1, you have to correct the injector's flow rating based on the pressure. Many people opt for Ford injectors, and they are generally flow rated at 39.15psi, so when you use them in an LT1 at 43.5psi, they flow about 5% more than they are rated at.

First, determine what size injectors you need. My guideline for a normally aspirated engine is to multiply FLYWHEEL (not rear wheel) HP by 0.07 to get the minimum acceptable size injector. If you think your engine will make 500HP at the flywheel, 500 X 0.07 = 35 #/HR.

The stock PCM can only drive "high impedance" injectors (12-15 ohms resistance, resulting in a 1 amp constant draw.) High impedance injectors are good for the sizes typically needed for our engines (42 #/HR max). For larger injectors, low impedance (also knows as "peak and hold") are better, because the low resistance (3-5ohms) results in a higher initial current draw (~5 amp) to open the injectors faster, and the injector current draw then drops to 1 amp. required to hold it open. In recent years, injectors larger than 42 #/HR have become available in high impedance, and you can buy an add-on "black box" that allows the stock LT1 PCM to drive a low impedance injector.

All this is TMI.

Don't get confused. First size the injector. You will need a high impedance injector. If you are buying an LS1 or a Ford injector, we can tell you what the flow rate will be, when operated in the stock LT1 43.5psi fuel system.

Going too small on the injectors will cause them to overheat and flow less than rated flow. Going too large is generally not a problem. The stock PCM seems to be able to handle 42 #/HR injectors, able to turn them down to the short pulse widths required to allow the engine to idle smoothly.

 

thank you that helps alot. so im prob going to go with a 36lb injector based on what you have told me. so know which do i go with?

 

If your calculations indicate that the 36# injector is best, I strongly suggest that you go with 42# injectors. They can be tuned to perform fine for your application, they give you room to grow later, and they are far more prevalent than 36# injectors.
AFA brands, there are many out there that are acceptable. I ran the Lucas 42# flow matched injectors for years with no issues at all.

 

i have a set of 36lbs i installed and ran 2 times before the tuner blew the engine. i went bigger and better and i have 62 now. 250 there yours

 

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