Carb to TBI conversion

[Dan Brown]

I am currently putting a TBI unit off a 1995 Chevy pickup with a 5.7 L engine on to a 1974 Chevy pickup with 5.7 L engine and have some questions about VSS and EGR. If anyone has done something like this, I would really like to hear from you.

Thx a lot
Dan Brown

[dave w]

TBI computers use a 2000 pulses per mile VSS square wave signal.

https://jagsthatrun.com/collections/tpi-tbi/products/speed-sensor-place-holder-4pac

The original 95 Chevy used a Vehicle Speed Sensor Buffer (VSSB) for the 95 Chevy dash speedometer and ABS braking system. The VSSB is not needed for the 74 Chevy if your using a TH400, TH350, or manual transmission. The 95 Chevy VSSB is needed if your going to use a 4L60E, 4L80E, or 700R4. If you have a 4L60E, 4L80E or 700R4 you should a VSS in the transmission, eliminating the need for the JTR aftermarket VSS. ****Some 700R4 transmissions Do Not Have a VSS.*****

Direction are supplied with the VSS or contact JTR tech support.

The EGR can be disabled in the chip programming by setting EGR "ON" at 151 degrees Celsius (304 Fahrenheit) and / or EGR "ON" at 255 MPH.

dave w

[Fast355]

I am currently putting a TBI unit off a 1995 Chevy pickup with a 5.7 L engine on to a 1974 Chevy pickup with 5.7 L engine and have some questions about VSS and EGR. If anyone has done something like this, I would really like to hear from you.

Thx a lot
Dan Brown

Don't forget the Park/Neutral input to the ECM. Painless makes a simple relay kit that uses the OEM park/neutral switch and provides both the correct signal for the ECM and Park/Neutral startup protection. Their kit is easy to duplicate with a relay and a diode as well.

[dave w]

Don't forget the Park/Neutral input to the ECM. Painless makes a simple relay kit that uses the OEM park/neutral switch and provides both the correct signal for the ECM and Park/Neutral startup protection. Their kit is easy to duplicate with a relay and a diode as well.

The 1995 16197427 Second Generation TBI computer does not have a Park / Neutral input wire like the older 1227747 First Generation TBI computer does.

I agree 100%, a Park / Neutral safety switch is a must have feature!

dave w

[Dan Brown]

I am using a Muncie SM465 which is a manual transmission, so, if I'm reading dave w right, I don't need a VSS. If this is correct, and I don't use one, will I have any driving problems? Too, as for the EGR, how do I handle that? I didn't bother to worry about an EGR valve when I started this project since the vehicle is over 40 years old and in Texas, it's exempt from any emissions check, but I'm now being told that if I don't use one, the MIL will be on constantly since the ECM isn't seeing an EGR signal. True/False?

[Fast355]

The 1995 16197427 Second Generation TBI computer does not have a Park / Neutral input wire like the older 1227747 First Generation TBI computer does.

I agree 100%, a Park / Neutral safety switch is a must have feature!

dave w

It does too!!! It uses one of the pressure sensor inputs from the E-Trans when it is in TCC only mode. It is in my wiring change chart.

The manual trans trucks use a clutch anticipate switch from what I remember too.

[Fast355]

I am using a Muncie SM465 which is a manual transmission, so, if I'm reading dave w right, I don't need a VSS. If this is correct, and I don't use one, will I have any driving problems? Too, as for the EGR, how do I handle that? I didn't bother to worry about an EGR valve when I started this project since the vehicle is over 40 years old and in Texas, it's exempt from any emissions check, but I'm now being told that if I don't use one, the MIL will be on constantly since the ECM isn't seeing an EGR signal. True/False?

You will want a VSS. You will not get away without tuning the ECM unless you run a factory 350 cam and factory TBI heads.

[c5wagner]

I actually just took off my jags that run 2000 pulse per mile vss sensor since i switched to the 4l60e and got their 40 pulse per revolution reluctor kit. PM and I'll send the 2000 ppm for $75 shipped.

[dave w]

I am using a Muncie SM465 which is a manual transmission, so, if I'm reading dave w right, I don't need a VSS. If this is correct, and I don't use one, will I have any driving problems? Too, as for the EGR, how do I handle that? I didn't bother to worry about an EGR valve when I started this project since the vehicle is over 40 years old and in Texas, it's exempt from any emissions check, but I'm now being told that if I don't use one, the MIL will be on constantly since the ECM isn't seeing an EGR signal. True/False?

What is the computer part number your using for the TBI conversion?

dave w

[dave w]

It does too!!! It uses one of the pressure sensor inputs from the E-Trans when it is in TCC only mode. It is in my wiring change chart.

The manual trans trucks use a clutch anticipate switch from what I remember too.

I can't find 16197427 wiring schematic showing a wire labeled Park / Neutral. Please post a 16197427 wiring schematic showing the Park / Neutral wire.

dave w

[Fast355]

I can't find 16197427 wiring schematic showing a wire labeled Park / Neutral. Please post a 16197427 wiring schematic showing the Park / Neutral wire.

dave w

Had to reference my old writeup on TGO. When you have TCC only option selected if you input the Park/Neutral wire into pin E5 the PCM will see Park/Neutral or In-Gear just as it should. It will operate the Idle Speed tables correctly and add or remove IAC counts to compensate for the load change. I always add enough steps to keep the engine from having a large RPM drop on the Park to Reverse shift. Reverse has the highest engine load. I set the Park/Neutral table about 75-100 rpm higher than in-gear. Makes the transition feel relatively seamless without the RPM dipping and activating the stall saver routine. I have yet to find a factory application that was TCC only so you would not find this on a wiring diagram. I figured out the TCC was on E10. The TCC only application did not seem to have coding for a High Gear switch or I never found it if it existed.

https://www.thirdgen.org/forums/tbi/442325-notes-information-converting-tbi.html

4.3 V6 with a 5speed wiring diagram should show where to input the clutch switch too. The PCM uses the clutch signal for the spark smoothing. The PCM will alter timing and IAC counts to help you launch off-idle and shift the trans more smoothly. The clutch switch will also keep the RPM from spiking when you press in the clutch pedal coming to a stop. The factory upshift light control is on pin E2 and is enabled when you select manual trans option. You can adjust the light to come on at various TPS vs RPM and set the NV table correctly for the SM465. I had it programmed correctly and functioning on a 3spd column shift truck. I used a relay to control an amber bulb.

[dave w]

Had to reference my old writeup on TGO. When you have TCC only option selected if you input the Park/Neutral wire into pin E5 the PCM will see Park/Neutral or In-Gear just as it should. It will operate the Idle Speed tables correctly and add or remove IAC counts to compensate for the load change. I always add enough steps to keep the engine from having a large RPM drop on the Park to Reverse shift. Reverse has the highest engine load. I set the Park/Neutral table about 75-100 rpm higher than in-gear. Makes the transition feel relatively seamless without the RPM dipping and activating the stall saver routine. I have yet to find a factory application that was TCC only so you would not find this on a wiring diagram. I figured out the TCC was on E10. The TCC only application did not seem to have coding for a High Gear switch or I never found it if it existed.

https://www.thirdgen.org/forums/tbi/442325-notes-information-converting-tbi.html



Pin E5 on the 16197427 is listed as "Range Signal C" on the Factory Wiring Diagrams. I'm hoping to avoid confusion. The 16197427 upgrade information on TGO has helped and benefited many TBI projects. :thumbsup::thumbsup:

Accurate information is helpful, but sometime too much information is confusing. I agree E5 can be used as a Park / Neutral input, but the chip needs to be reprogrammed (as stated in a previous post). Can confusion be created when re-purposing a computer wire with a custom chip (maybe / maybe not)? It is a 100% accurate statement to say the Factory Wiring Diagrams for the 16197427 DO NOT list a Park / Neutral input wire.

TBI conversions can be challenging for someone if it's their first time doing a TBI conversion. I created confusion in a previous post on what Transmissions used a VSS and what transmissions used a VSSB. Maybe confusion can be avoided by asking "what transmission is in the 74 Chevy" before answering a VSS is question. In hindsight an answer saying a SM465 requires a VSS could have avoided confusion?

dave w

[Dan Brown]

So dave w, your saying that I WILL need a VSS using the SM465, and if so what do you recommend I do? Too, I am using a 16197427 ECM.

[c5wagner]

A VSS is a must in my opinion because the decelerator fuel cut off (DFCO) and a few other speed controlled things like EGR and stuff. The confusion above is that a 4l60e or 4l80e electronically controlled automatic needs a vehicle speed signal buffer to handle the VSS signal to the ECM to control the trans. Non PCM controlled trans like: TH350, TH400, 700r4, sm465, sm420 and etc would only need a VSS for the engine control like DFCO and etc. In tunerpro, you would specify speed signal not from DRAC and need a 2000 pulse per miles VSS like the 2prs from jags that run and set it for manual transmission options.

[Fast355]

So dave w, your saying that I WILL need a VSS using the SM465, and if so what do you recommend I do? Too, I am using a 16197427 ECM.

Needs a VSS and programmed for manual trans option. I will double check the information and wiring diagrams for the clutch switch. The relay option I mentioned to use the OEM clutch safety switch will also work for a clutch input signal from what I remember.

[dave w]

So dave w, your saying that I WILL need a VSS using the SM465, and if so what do you recommend I do? Too, I am using a 16197427 ECM.

Yes the SM 465 / 16197427 combination requires a VSS.

TBI computers use a 2000 pulses per mile VSS square wave signal.

https://jagsthatrun.com/collections/...ce-holder-4pac

dave w

[Dan Brown]

I already have a Jags That Run 2prs speed sensor that will drive thru the speedometer cable attached to the back of the transfer case. The guy at JTR told me that one of the white wires on the speed sensor is a ground and the other attaches to one of two wires coming from the ECM. He wasn't sure which of the two wires coming from the ECM to connect to the other white wire on the speed sensor. On my system, and per the wiring diagram I'm using the two wires coming from the ECM, one of which is coming from F2 HI, and is red/black, the other is coming from F3 LO, and is dk. blue/white. If I attach one of those wires to the other white wire on the speed sensor, will that work. Too, which of the two wires coming from the ECM do I use, the red/black one, or the dk. blue/white one? Thx for any help.

[c5wagner]

Pin F13, my wire was dark blue without white...

[Dan Brown]

I see the dark blue wire on F13 and a brown wire on F12. What is the brown wire for, and what does it and the blue wire have to do with the 2prs speed sensor?

[c5wagner]

Ignore the brown wire, it is for electronically controlled transmissions. Just hook the 2prs to F13.

[Dan Brown]

So, by hooking the 2prs to F13 and grounding the other white wire, I won't need any kind of buffer?

[Dan Brown]

Too, will I need to have to have my ECM reprogramed to tell it there is no automatic transmission?

[c5wagner]

So, by hooking the 2prs to F13 and grounding the other white wire, I won't need any kind of buffer?
Correct

Too, will I need to have to have my ECM reprogramed to tell it there is no automatic transmission?
There will need to be some tuning involved with any non stock applications without swirl port TBI heads and camshaft, reprogramming to get rid of the automatic will just mostly get rid of codes but should be done anyway.

[Dan Brown]

If I need ECM tuning, can it be done thru the ALDL or will the ECM need to be removed. Too, what difference does it make what heads or cam I have and how does the ECM know?

[dave w]

If I need ECM tuning, can it be done thru the ALDL or will the ECM need to be removed. Too, what difference does it make what heads or cam I have and how does the ECM know?

There are hardware options for tuning. I opted for the Moates.net Ostrich 2.0, which for all practical purposes make the 16197427 a FLASH computer. The Ostrich 2.0 can be flashed, even when driving down the road.:thumbsup: The Ostrich 2.0 is a chip emulator so it eliminates the chip.:thumbsup::thumbsup: Plug the USB into the laptop and Ostrich 2.0 and flash the tune.

Link to Moates.net Ostrich 2.0: http://www.moates.net/ostrich-20-the-new-breed-p-169.html

dave w

[Dan Brown]

Does anybody know someone who has the equipment and knowledge to do this tuning?

[Dan Brown]

I should have said that I live in the Houston Texas area.

[Dan Brown]

Could you please contact me as I'd really like to talk to you. Let me know if we can talk and we'll exchange contact information. I live in Katy.

[Dan Brown]

I have now changed my ECM to a 1227747. I was told that the 16197424, which I now have, was OBD2 as it has red and blue connectors and I want OBD1. Was also told the the 1227747 does not have electronic transmission control capabilities, which I don't need anyway as I have a Muncie SM465. Does anybody have any experience with this combination? Also, do I need a VSS with this combination?

[1project2many]

Hi Dan,

I am unable to locate a 16197424 ecm. The 16196396 ecm is an OBDI C3 ecm used with many manual transmission TBI trucks from 93-95. It is actually an "older" generation computer. Automatic equipped trucks received a 16197427 OBDI pcm, which is a newer generation pcm and is much more capable than the old C3 ecm's. The 1227747 was used in many 88-92 trucks with or without automatic transmission. Any of these computers will operate your engine. The C3 computers such as the 1227747 really, really need a working VSS to provide best performance IMO. I have a 1957 Chevrolet truck with 5.0 TBI and manual transmission. I started with a very old computer from an '83 Camaro, migrated to a 1227747, then moved to a 16197427. I am happy with the consistent performance of the 7427.

[Six_Shooter]

I have now changed my ECM to a 1227747. I was told that the 16197424, which I now have, was OBD2 as it has red and blue connectors and I want OBD1. Was also told the the 1227747 does not have electronic transmission control capabilities, which I don't need anyway as I have a Muncie SM465. Does anybody have any experience with this combination? Also, do I need a VSS with this combination?

Did you mean 16197427?

That would be an OBD1 PCM and would be what I would use over the 7747. It has MUCH faster coms for better datalogging, more tuneability, and just a better overall ECM IMO.

[Dan Brown]

Using a 1227747 ECM to install a TBI on my 1974 Chevy K10. While studying the ECM wiring schematic I see pin C9 with a purple wire coming from the starter solenoid called "crank signal input". Is this to let the ECM know that the engine is cranking and is it needed?

[1project2many]

The crank signal should be connected. I connected it to the S terminal of the starter.

[Dan Brown]

My schematic also shows the purple wire going thru a 3 amp fuse. Is this correct?

[dave w]

My schematic also shows the purple wire going thru a 3 amp fuse. Is this correct?

Yes

dave w

[Dan Brown]

Thx Dave.

[Six_Shooter]

It's not absolutely necessary. I've used the '7747 with and without that connection and haven't experienced any difference in starting.

I mean, it's not a difficult connection to make so add it, but all I'm saying is, if you didn't, you're not likely going to experience issues starting.

[Dan Brown]

I've already installed it.

[clarkent5477]

I've already installed it.

How is it going? I just converted my 66 Cadillac 429 to TBI injection using a 1227747 PCM. I'm going to use the 2000 PPM Jag VSS, but wondering if the stock cruise+DRAC will work with that. That's down the road some; we'll see.

[Dan Brown]

I am putting a GM TBI unit in my 1974 K10 and am using the 1227747 ECM. I'm trying to make the check engine light come on and per the ECM schematic I need 12v switched to the bulb and a brown/white wire going to pin A5 which grounds out inside the EMC. I've checked everything I can think of, good bulb that works, 12v to the bulb, and the light won't come on. Does this mean the ECM is bad or could it be something else

[stew86MCSS396]

In response to your same question on TGO...double, triple, quadruple check your wiring. Idk what schematics you have that would have the A5 spliced to go to pin D on the ALDL... There's some schematics at the following link... http://www.gearhead-efi.com/Fuel-Injection/showthread.php?304-1227747-ECM-Information-42

[Dan Brown]

In the 1227747 schematics you sent me, the schematic on the top row far right is the schematic I have which shows the spliced brown/white wire going to pin D in the ALDL.

[dave w]

Found the attached .pdf on the web, looks correct to me.

[Dan Brown]

Okay, thx a lot, looks just like the way mine is currently wired. Now, since my check engine light won't come on, is there anything else that could be causing it to not come on besides a failure inside the ECM?

[stew86MCSS396]

In the 1227747 schematics you sent me, the schematic on the top row far right is the schematic I have which shows the spliced brown/white wire going to pin D in the ALDL.
Ahhhh...I didn't see that and ironically albeit not originally 1227747 but it would be plug and play, my '85 Caballero has a brown/wht wire going to ALDL D. I have no idea if it's spliced as you have said. I keyed on engine off and measured for volts and only got 0.1v. I verified that my ground was good checking volts on the cigarette lighter.

Edit: Wait a minute, the last schematic says it should read 0v with key on eng off but 14v with engine running.

[Dan Brown]

I'm not sure I'm following what you are saying about the brown/white wire going to pin D in the ALDL, but I still can't make the check engine light come on knowing that the bulb is good and there is 12 volts going to the bulb and the brown/white wire has continuity all the way to pin A5 at the ECM. With the ignition on, and 12 volts getting to the bulb, does anybody have any idea what I should see at pin A5 if I back probe it?

[stew86MCSS396]

On my vehicle, I do have continuity from ALDL D to ECM A5. If you back probe A5 with the key on engine off, it should be 0v. If it's showing voltage, perhaps the ECM thinks the engine is running??? Idk what the ECM looks for when that happens, maybe distributor ref pulse? I'm sure there's a number of ways to force a CEL by disconnecting a sensor.

[Dan Brown]

Okay, my engines not running as it's not ready to start yet, but, I do currently have 12.5 volts on A5 at the ECM connector. Anybody have any idea why?

[Dan Brown]

I think I'm on to something. I bought another ECM from Ebay and it makes the light come on. However, I'm not sure the two removable components are compatible with a 350 (5.7L). Can somebody tell me the correct numbers for these components. Right now the smaller removable component of mine is 16051637 and the one that turns the light on is 1606837. The larger removable component is 6D12 3466 and the one that turns the light on is AMTU. Too, there is sticker with a bar code on it, the ECM that won't turn the light on has the number 427561314838156 and the one that turns the light on is 427561100178190. Do these numbers tell anybody anything. Thx a lot.

[Dan Brown]

Okay, I think I'm good. I swapped both components, which were for the 350, from my original ECM that wouldn't turn the light on to the one I just bought and now the light not only works, when I plug in a code scanner it flashes and continues to flash 12 as long as I keep it plugged in. Now I only hope that when I get the engine started it keeps flashing 12. Fingers crossed.