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Thread: Hilborn 8-stack conversion to EFI

  1. #1
    Carb and Points!
    Join Date
    Jan 2021

    Hilborn 8-stack conversion to EFI

    I have a Hilborn injection manifold like the one we used in our drag car in the 60s.
    I want to convert it to electronic so I can run it on the street.
    I'm hoping to get some input as to which injectors, pump, and ecm I need, and everything else to do this conversion.
    I really want to do this myself as I'm retired and have the time and can't justify the $ having it done by someone else.

    inj 2-16 b.jpginj 2 -16.jpgEarly T at Lions.jpg

  2. #2
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Mechanically thinking, there's not much room to retro-fit an injector into the manifold pictured.

    Maybe the Edelbrock Pico Fuel injectors are an option?

    dave w


    Last edited by dave w; 02-17-2021 at 04:31 PM.

  3. #3
    Super Moderator Six_Shooter's Avatar
    Join Date
    Feb 2011
    Most Hilborn conversions place the injectors on the inside of the manifold.

    Size the injectors to your expected power. There are a few ways to mount and plumb them, welding in bungs and then making fuel rails is a common approach, there are also injector mounts that will support each injector individually, and allow each to be plumbed on their own, which can be good if you want to keep a slightly old school look, with a tube or hose to each injector.

    TPS can be mounted in a few spots, most commonly on the end of one of the throttle shafts. On my own setup, I made a mount where the barrel valve would've been, to keep a bit of an old school look.

    Fuel pumps can be basically any that will support your power. If you're making under 500 HP, then a Walbro 255 is a good option. I've been running one for about 13 years on one of my cars, and have made about 400 HP with it so far. They can also be doubled up to provide more flow if your power goals are higher and the pumps could be staged to use one when low power demands are needed and kick the second on when more power is being made.

    As far as ECU goes, I had considered using a GM OBD1 ECM for my setup, but I am/will be using a Megasquirt MS3X with my converted Crower setup. I have an MS3X on one of my other cars right now, and will using another MS3X on a 3rd vehicle of mine, once I get it back together. The MS offers Alpha-N mode for tuning that uses just a TPS sensor for "load", it also has an ITB mode that combines both Alpha-N and Speed Density type tuning.
    A couple reasons I decided against using a GM ECM, is that the GM ECM doesn't like it when an IAC isn't installed and/or working, and will at the very least blow codes (which CAN be disabled), but from some testing would also not run quite right, even with the codes disabled. There's also only Speed Density type tuning available, and if switching to Alpha-N is desired isn't exactly easy and on some ECMs not possible.

    Which brings up another issue that will have to be decided on how to deal with it before doing anything... the fuel pressure regulation. If the injectors are located below the throttle plates, which is generally desired for good idle, then a vacuum referenced FPR will also be desired, which means that you will need to attach a hose to each runner and plumb them to a common hose to go to the FPR, the good thing about this is that you can T it to go to a MAP sensor as well, for load reference for the ECU. This vacuum tree can be done above the manifold or below. On my own setup, I welt below to keep it all as hidden as possible, then comes out through the manifold base near the distributor and splits there to go to the ECU and the FPR.

    You could also place the injectors above the throttle plates, as a many mechanical setups do, this won't require any vacuum reference, but does generally have poorer idle quality and can be a bit tricky to tune. Great for high RPM though.
    The man who says something is impossible, is usually interrupted by the man doing it.

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