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Thread: Help with finding injectors for LS7.

  1. #1

    Default Help with finding injectors for LS7.

    I'm trying to figure out the best direction to go with my situation. I'm working on a custom 69 Camaro with a MAST black label LS7 675HP engine. The shop that built the car had another EFI setup on it, which I replaced with a Dominator setup.

    The fuel system is returnless that runs at 4 bar. I originally was going to use ID1050X instead of the FAST 39 lb/hr that were in the car. Problem is ID is unable to give me 4 bar, returnless data for the Holley, which has put me in a spot.

    I have the car running on a set of stock LS7 injectors which are rated at 42.9 @ 4 bar per the data from Holley. I dynoed the car before I put the Holley on it and it made 606/515 wheel.

    I'm worried that the stock injectors won't be enough be enough. If I want to use the IDs I'm going to have to convert it to a return style system, which I DO NOT want to do, not on this car.

    The factory injectors are 34mm long. It's using the stock rails and has a custom air cleaner assembly that bolts to the fuel rails, that sits on top of the intake. If I want to keep that I have to stay with the factory rails. However, I would gladly put rails on it and change the air cleaner setup on before I would put a return fuel system on it.

    Any input or suggestions would greatly appreciated. J

  2. #2

    Default

    J, I don't recall exactly, but I do believe that the LS9 injectors are bigger and are exactly the same physically as the LS7 injectors. Double check that, as I'm not 100% certain, but it's something to investigate. Andrew

  3. #3

    Default

    I want to thank you. You're 100% correct. They're 56 lb/hr @ 4 bar and the same length. I'll check with Holley to see if they have any data for them. If they do, that's the route I will probably go. It would make my life much easier.

    Something I just thought about, do the LS9 injectors have a different spray angle on them because they sit in the blower? For some reason, I "think" I remember reading that a long time ago.

  4. #4

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    Well, what's the comparable lb/hr of the LS7 injectors, if the car had 39 lb/hr FAST injectors in it?

  5. #5

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    I don't know if the 39 lb/hr injectors are at 3 or 4 bar. I won't use FAST injectors for several reasons, but that's for another time.

  6. #6
    Join Date
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    Question

    Quote Originally Posted by Jay@HAP View Post
    I originally was going to use ID1050X instead of the FAST 39 lb/hr that were in the car. Problem is ID is unable to give me 4 bar, returnless data for the Holley, which has put me in a spot.
    I have the car running on a set of stock LS7 injectors which are rated at 42.9 @ 4 bar per the data from Holley. I dynoed the car before I put the Holley on it and it made 606/515 wheel. J
    606 HP at the wheel, and 675 "rated" on 39 lb/hr, isn't bad.
    You put 42s in it. Can you dyno it with the new injectors, and look at the PW, and determine their suitability? What did the dyno show with the 39s?
    Injector Inspector
    USAF 1960-1964
    Drag racing since 1955

  7. #7
    Join Date
    Nov 2014
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    Default

    Was the actual AFR getting to your Target AFR, and what was the Duty Cycle at? If DC is close to 100%, and you're not reaching your Target AFR, your injectors are too small.

  8. #8

    Default

    Quote Originally Posted by 81 TransAm View Post
    Was the actual AFR getting to your Target AFR, and what was the Duty Cycle at? If DC is close to 100%, and you're not reaching your Target AFR, your injectors are too small.
    I don't know what it was. The ECU that was in it wouldn't stay connected to the laptop while the car was running, so I had no way to datalog it.
    I think I'm going to use the LS7 injectors and see what the duty cycle is. The FAST 39 lb/hr are what come in that MAST engine and the LS7s are tad bigger.
    When I started this project, I got the IDs to replace the FAST 39 lb/hr. Then I found out the LS7 intake was on the car was cracked and bought a replacement from GM.
    It came with everything, injectors, rails, TB, etc. So that's how I ended up with the LS7 injectors.
    After I get it on the dyno, I'll know if they are going to work. I "think" that MAST wouldn't use injectors in their crate engines that are too small.
    I did do some reading and found the LS9 injectors do have an angled spray pattern because they sit in the blower, so those are off the list.
    I appreciate everyone's input & time.

  9. #9

    Default

    Quote Originally Posted by Jay@HAP View Post
    I did do some reading and found the LS9 injectors do have an angled spray pattern because they sit in the blower, so those are off the list.
    I doubt you would see any adverse effects from this. Andrew

  10. #10
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    Default

    You can set it up to do internal datalogs. I use both methods, laptop & internal (ECU).

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