1999 Gen VI EFI to Q Jet 4L80E

[BeXtreme]

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.

Nope, trans only needs RPM and TPS. I would personally do an 0411 swap and get the $60 tool whether I did the carb swap or not. That lets you do the trans tuning and get rid of all the engine related codes you will get from removing the EFI and timing related things. You can also keep the vortec distributor and leave the 4x reluctor and continue to use the computer to get detonation protection and adjust timing while still swapping the EFI for carb... but again, you would then be losing all of the benefits of EFI just to make it harder to tune and drive.

 

[amrush2112]

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.

Or there might be the slight possibility that some of us old timers might have a bunch of parts laying around and don't have to spend very much at all. No matter how much preface I try to make there is always and I do mean ALWAYS that one that just can't resist to throw there two cents in. Well I guess that just goes with the territory. But the middle of your response was the EXACT answer that I was looking for. Thank you! And I do really have a ton of parts laying around so this part wont cost much. BTW if I change the cam I would be doing a double or a true roller timing chain anyways. Mandatory! But to change tune ability on the factory unit is a NO go. I would have to reflash it and its very limited. The factory intake is not very good for hp and would have to be changed. The stock ECU would be changed for a Holley Terminator Max unit plus intake AND injectors and now we are talking $2500.00. No math genius but this is still less expensive.

 

[BeXtreme]

But to change tune ability on the factory unit is a NO go. I would have to reflash it and its very limited. The factory intake is not very good for hp and would have to be changed. The stock ECU would be changed for a Holley Terminator Max unit plus intake AND injectors and now we are talking $2500.00. No math genius but this is still less expensive.

You wouldn't need to do any of that. 0411 swap and tool for ~$150... tune for whatever you want. No reason to go to a terminator max setup unless you are planning on full race and 800+hp. Anything over ~500-550hp and >6000rpm and you would need to swap to an aftermarket single plane MPFI with throttle body($700-$7000 depending on how hard core you are going). If you are wanting to use the truck for racing and fun, then sure. If you are wanting to use it for truck stuff and daily driving... then you are really going backwards.

These comments aren't really meant to hate on the carb swap, just pointing out that your VERY FIRST post said you were terrible with computers and electronics. You are talking about doing the thing that is going to require enough knowledge and skill to hack apart the stock system and slap several different parts together into a cohesive whole. The reason these things usually degrade down into "there is always some haters wanting to give their 2 cents" is because we have done it, and have seen enough people do it, to know that the very reason you want to switch to carb is exactly the reason you are likely to have major issues.

It's a lot more complicated than it appears at first glance depending on how much you are willing to compromise. Do you want all of the things in the truck to function as they did before? Cruise control? AC? Keeping the OD? Want all of the stock gauges to continue to function? The simplest and easiest solution if you are wanting big HP and ease of use with what you already have is to just pull out the entire harness and swap to the carb/HEI and buy a standalone trans controller. You might not be able to retain a working speedometer and cruise control if you do that without getting creative. The stock PCM controls a lot of things though, so just be warned that there might be other things that stop working as well.

 

[amrush2112]

The truck is not my daily driver. Yes it will be getting some crazy things. I have another daily driver 93 with a small block that is my driver and an 86 K20 with a 350 as well. I also have a 97 Land Cruiser with a bone stock 6.0 LS motor and 4l80E going in it with a Holley Terminator Max running it. Eventually it is getting some upgrades but I just don't see the need to buy efi systems for all of our vehicles. I have an 0411 computer and did look into it but decided that for what I want to do with the truck and what my comfort zone is that I feel more at home with a carb than efi. I was not bashing those that thought I was wasting money. I DID preface in my very first post all the reasons why so it seemed pointless to try to point out what I already stated was my reasoning. Its like trying to switch someones mind based on your set of facts and your comfort zone but not mine. I am in my element making a q jet or a carter (edelbrock) or a holley 4150 carb dialed in on just about anything. I do appreciate what a computer does but for what my needs are it is just not what I am looking for. Good for most and some but I don't fall in that category.

 

[Scooterwrench]

Hey man,I'm with you. Q-jet is the sh*t. The only problem I have with mine is fuel ethanol fuel vaporization after I shut the motor off for a few minutes. I always have to do a clear flood on hot restart. Once I put that motor in my 91 C1500 I'll have enough hood clearance to stack up another 1/4" carb insulator and hopefully that problem will go away.
What about going to a non-electronic tranny for your truck?

 

[amrush2112]

Hey man,I'm with you. Q-jet is the sh*t. The only problem I have with mine is fuel ethanol fuel vaporization after I shut the motor off for a few minutes. I always have to do a clear flood on hot restart. Once I put that motor in my 91 C1500 I'll have enough hood clearance to stack up another 1/4" carb insulator and hopefully that problem will go away.
What about going to a non-electronic tranny for your truck?

I thought about doing that but too expensive. A 700R4 would work but would have to modify quite a bit to make it work. Drive shaft and other things just make me say no. I would think that as long as you ran the fuel pump long enough to keep the bowls filled then it should work. Also the stock warm start issues with the factory FI on the 7.4 will be resolved. It has a hard time starting when warm due to programming and injector issues from the factory. Won't miss that at all.

 

[Moleman]

I thought about doing that but too expensive. A 700R4 would work but would have to modify quite a bit to make it work. Drive shaft and other things just make me say no. I would think that as long as you ran the fuel pump long enough to keep the bowls filled then it should work. Also the stock warm start issues with the factory FI on the 7.4 will be resolved. It has a hard time starting when warm due to programming and injector issues from the factory. Won't miss that at all.

I did the carb conversion on my 92 its not all that bad to do . I don't have the later model truck though. So I can't really say how much more difficult it is. I know on the tbi harness it's like 4 wires and I had it running in in about a day 1/2. But I wired my fuel pump straight off the relay.

I don't know how you would regulate your fuel pressure though i think the newer pump would overload the holley style bypass regulator. I think you need a stronger spring or something.

 

[Erik the Awful]

I'm pretty sure the fuel pump doesn't flow enough fuel to overpower the spring. Remember, the fuel pressure regulator itself is what develops the pressure. The pump merely provides the flow. So long as the FPR can bypass the volume of fluid it will regulate the pressure.

 

[Supercharged111]

Nope, trans only needs RPM and TPS. I would personally do an 0411 swap and get the $60 tool whether I did the carb swap or not. That lets you do the trans tuning and get rid of all the engine related codes you will get from removing the EFI and timing related things. You can also keep the vortec distributor and leave the 4x reluctor and continue to use the computer to get detonation protection and adjust timing while still swapping the EFI for carb... but again, you would then be losing all of the benefits of EFI just to make it harder to tune and drive.

You also need MAP, MAF, and ECT for full functionality. MAP and MAF will calculate the load and determine line pressures, TPS is there for your shift points. If it can't calculate load, it's going to default to full line pressure. The TBI stuff is different. If you give it MAP but not MAF, it'll still default to max line pressure. With a 411 and custom OS, you can do MAP only and have it not max out the line pressure. ECT will change up shifting and TCC lock when it gets hot, and frankly I'm not sure what will happen without ECT because if it's too cold it won't even lock the TCC.

 

[Moleman]

I'm pretty sure the fuel pump doesn't flow enough fuel to overpower the spring. Remember, the fuel pressure regulator itself is what develops the pressure. The pump merely provides the flow. So long as the FPR can bypass the volume of fluid it will regulate the pressure.

50-60 psi is a lot to regulate to 5 psi though.