1999 Gen VI EFI to Q Jet 4L80E

[amrush2112]

OK so I am working on this plan to swap all the EFI on the K2500 7.4 Suburban. I had originally planned to go with the Terminator EFI setup and now I am deciding to go back old school on it. Now before all the "haters" come out and instruct me on how this is dumb, idiotic, or ask why am I doing this, let me give some back story so we can dispel that before it even starts lol.

First and foremost, I am old! Yes back when they invented the wheel old! My diagnostic skills are FAR better on 4 barrels and some hand tools and a vacuum gauge than trying to diagnose a computer. No I don't still carry a beeper. I quit working on my old muscle cars back about 94. Since then it has just been maintenance on my daily drivers.

Second - all my vehicles now have carburetors. 1968 GTO, 93 Silverado (ex diesel car with at 350 4bbl), 86 K20 Suburban with a 350, and my 99 7.4 K2500.

Yes I know that there are a bunch more things I can do with EFI and its the best thing since sliced bread. Blah blah blah. I get it. Just not my thing.

Now those about the emissions fail mandatory warning naysayers. 1 - Live in Texas. 2 - Non Emission check county residence - safety only required. 3 - On vehicles 25 years or older in Texas its only safety inspection check state wide. 4 - I'm no math genius here but 2023-1999 = 24 years.....soooo about to have its 25th birthday. Yay!

Ok since that's all out of the way.... I've seen lots of tbi to carb posts with the 4l60e transmission and based on that I can see its fairly straight forward as to how the setup is.

1 - Old school HEI required
2 - Carb with a tps sensor utilized. Holley, Edelbrock, and even HEI will work.
3 - splice into factory wiring to give a tach signal to computer and trans.
4 - throttle cable shortening and bracket modifications to work.

My questions are (long way to get here but here we are) ....

1. Has anyone done this swap on a 7.4 Gen VI post 96 454 with any success? Or am I the first? Surely not.
2. If I am still maintaining the factory ECM to run some things in theory it should still run the trans as long as it gets the signal from the tach?


Sorry for the long winded post but I have seen a few of these where inquiries were made only to receive a ton of flack for going backwards. Like I said, I'm an old-timer and if I were to never have grown up tuning carbs I would be concerned with dialing them in for street but that's ALL I USED TO DO!

Thanks for all the help!

Now let the fun begin! GO!

 

[Spareparts]

I believe it will need a TPS sensor and Tach sensor. You could also go this route that im pretty close to doing also and dumping all the FI Stuff.
I do love a good carb setup and know how to make em run fine but i also kinda wanna get HP Tuners and learn that also.

US Shift Stand-Alone Transmission Controllers

US Shift Electronic Transmission Control Systems let you take charge of your 6R80, 4R70W, E4OD, 4R100, 4L60E, or 4L80E transmission and unlock its true potential. Our transmission controllers are compact, packed with features, and have a built-in display for tuning as well as user-friendly...

www.usshift.com

 

[amrush2112]

I did look into HP tuners and after a bit I realized it just wasn't for me. I plan on changing the cam and long tube headers. I have a 1 ton ford Solid Dana 60 front and leaf springs that I am changing out once I can finish my shop and install the lift. Have all the parts but just don't like laying on my back doing all that stuff. Too old. Lol.

I remember your suburban when I first bought mine and you commented on mine back then. I believe they are damn near identical trucks in drivetrains!

 

[amrush2112]

I believe it will need a TPS sensor and Tach sensor. You could also go this route that im pretty close to doing also and dumping all the FI Stuff.
I do love a good carb setup and know how to make em run fine but i also kinda wanna get HP Tuners and learn that also.

US Shift Stand-Alone Transmission Controllers

US Shift Electronic Transmission Control Systems let you take charge of your 6R80, 4R70W, E4OD, 4R100, 4L60E, or 4L80E transmission and unlock its true potential. Our transmission controllers are compact, packed with features, and have a built-in display for tuning as well as user-friendly...

www.usshift.com

I actually just spoke with them (US Shift) the other day and they are very nice units! Still working through the due diligence and I believe I can possibly use the stock tps sensor and modify the bracket to work with my q - Jet. Not 100% on it but am looking into it.

 

[Spareparts]

I think Edelbrock or Holly sells a bracket that might work?

 

[454cid]

Is there something wrong that you're trying to fix? I've hardly had to do anything fuel system related to my 300K miles 454.

 

[amrush2112]

Is there something wrong that you're trying to fix? I've hardly had to do anything fuel system related to my 300K miles 454.

Why yes there is! It doesn't have a 4 bbl on it. I have been looking all under the hood for that air cleaner but the closest thing is a big square box by the battery but when I open it up it doesn't have a carburetor under it!

 

[amrush2112]

Is there something wrong that you're trying to fix? I've hardly had to do anything fuel system related to my 300K miles 454.

Is there something wrong that you're trying to fix? I've hardly had to do anything fuel system related to my 300K miles 454.

Lack of freedom to control the tune on it. Me needing to change the camshaft profile and exhaust and such without spending $$$$$ on a computer just to do it.

 

[BeXtreme]

This cracks me up. At this point the tuning software is free for these things. It only takes a $60 tool to be able to do almost anything you want to it. I get the desire to want to simplify it, but the complexity of properly hacking and splicing into the stock harness without causing yourself even more problems is not insubstantial.

My thought, if you end up doing this, would be to get an Edelbrock RPM Air gap intake and the carb of your choice. Get yourself a basic HEI and a TPS for the carb. When you change the cam, pull the 4x reluctor off the crank and replace with a double roller timing set. Keep the majority of the harness and stuff intact. Splice into the tach wire to the ECU with the tach signal from the HEI. Run the TPS sensor on the carb to the TPS wires into the ECU. Adapt the cruise control cable wire to the carb, and you are done. All of your gauges should still work. Cruise control should still work. Trans should shift like stock.

You'll end up spending just as much to buy needles and jets to tune the carb as you would have on the tool to be able to tune your stock vehicle. You'll be spending about 4x as much just to convert the engine to carb... but whatever.

 

[Schurkey]

You'll be spending about 4x as much just to convert the engine to carb... but whatever.

WAY more than that. And I'd expect the stock ECU will need more than just an RPM signal and throttle-position signal. MAP for load, CTS for engine temp--both of those will affect shift timing. No O2 sensors will set code(s).

Some folks just need to screw-up a perfectly-good system.