Tbi swap build thread

[Jonboy]

Take a look at the original wiring from your truck. I think the NSS should hook into the switch on the clutch pedal, and there should be a reverse switch on the trans.

[FRENCHBLUE72]

Hey kevin what did you do to hook up the vss?

[Tx Firefighter]

I'm using the instrument cluster out of the 87 donor truck. It has a built in VSS that plugs into the factory harness.

[FRENCHBLUE72]

I see thanks... Does anyone know if the performance of the motor will suffer if the vss is not hooked up?

[rfmaster]

Originally Posted by FRENCHBLUE72

I see thanks... Does anyone know if the performance of the motor will suffer if the vss is not hooked up?

A simple answer is yes - there are number of operational parameters (depending on calibration) related to CCP, EGR, AE and PE enrichment routines triggered by VSS data. In other words without VSS input ECM believes that truck is stationary and you are simply revving engine up.

//RF

[FRENCHBLUE72]

So I guess the question is how would I fix it? I have the motor and tranny (1987 tbi )combo in a 82 toyota truck with no speedo? Is there a simple fix or should I just pull out the rest of my hair now?

[Jonboy]

I used a VSS from Jags that run. It was $75, and screws to the side of the transmission, in line with the speedometer cable. Something else to consider is that your TCC will not work without a VSS, and that could lead to transmission failure due to overheating the fluid from the slipping clutch over time.

[FRENCHBLUE72]

My trans is a th350 I should have mentioned that I swapped that in..

[FritzA]

I just wanted to add a couple things I learned about the DRAC.

First, Dakota Digital makes a version of the DRAC called the SGI-5. It is a lot easier to adjust than the chevy one, works with lot's of different VSS signals and has different output signals as well. No soldering! Summit has it for $75. Not a bad deal. You can download the pdf installation manual and read up on it.

Second, I thought I was going to need the DRAC/SGI-5 then I decided to go with an Autometer electric speedo. Suprise suprise.....it accepts various VSS inputs, is adjustable and has a DC Square wave output tab to feed my 1990 ECM. I don't need the DRAC or SGI-5!! A lot less wiring to do. I do not have a cruise control so this is all I need. I just saved $75, can you tell I'm excited?

[rfmaster]

Originally Posted by FritzA

I just wanted to add a couple things I learned about the DRAC.

First, Dakota Digital makes a version of the DRAC called the SGI-5. It is a lot easier to adjust than the chevy one, works with lot's of different VSS signals and has different output signals as well. No soldering! Summit has it for $75. Not a bad deal. You can download the pdf installation manual and read up on it.

Second, I thought I was going to need the DRAC/SGI-5 then I decided to go with an Autometer electric speedo. Suprise suprise.....it accepts various VSS inputs, is adjustable and has a DC Square wave output tab to feed my 1990 ECM. I don't need the DRAC or SGI-5!! A lot less wiring to do. I do not have a cruise control so this is all I need. I just saved $75, can you tell I'm excited?

That's a very good point - however if you are using Autometer speedometer you are still dependent on VSS (5291 or what is available ) to provide correct number of pulses per mile traveled to ECM. For example, if you are working with 87 to 92 TBI system a 2000 ppm VSS (open collector) is required. If you are using 5291 VSS the speedometer output terminal provides buffered +5 volt DC Square wave signal. In other words VSS must match what ECM is expecting to receive.
The SGI-5 appears to be a "Swiss knife" between VSS and ECM/PCM. The later PCM's (93-95) actually required two speed input signals - DRAC provided these signals. I am starting to spend more time with 7427 PCM which expects two VSS signals (transmission input signal and vehicle speed).

//RF

[FritzA]

No, it is not dependent on the VSS to send the signal at the correct output. Both the Autometer electric speedo and the DD SGI-5 accept inputs at different signals but have an output tab that is converted to the DC Square Wave for the older ECMs like mine.

[rfmaster]

Originally Posted by FritzA

No, it is not dependent on the VSS to send the signal at the correct output. Both the Autometer electric speedo and the DD SGI-5 accept inputs at different signals but have an output tab that is converted to the DC Square Wave for the older ECMs like mine.

The input VSS signal can be either AC or DC - installation instructions for Autometer Spedometer clearly state that: 500 to 400,000 pulses per mile (ppm). However, there is no mention if buffered output from the speedometer can be altered (change pulse rate or signal wave form) to match ECM/PCM requirements. Instead, in the note they just mention the following:
NOTE: This speedometer provides an output (OUT) terminal that can
be used with late model vehicle installations using the existing Vehicle
Speed Sensor (VSS). In these installations, the VSS signal wire should
be connected to the SIG terminal of the speedometer only. The OUT
terminal should then be connected to where the VSS output was
originally wired. This will provide a buffered VSS signal to the PCM/
computer in the vehicle.

From retrofit perspective - it is important to be able to work with various VSS flavors - for example early TBI ECM's expects 2000 ppm oc signal, some TPI ECM need 4000 ppm AC and so on. After market VSS can be either AC or oc 2000, 4000, 16000ppm and so on. So, from that view point SGI-5 is a must have...

//RF

[FritzA]

We are close to being in agreement.

I did not say the Autometer output is variable. I said it has a "DC square wave" output.

My instructions from Autometer say the putput is "+5 volt DC Square wave signal". It is not variable, it is the only output option no matter what the VSS input into the speedometer is. But for my 1990 ECM that output is just right.

So no, I do not believe the SGI-5 is a must have for my situation.

[dropd80s]

I have a few questions I could use some clarification on. I have decided to use a E2000 style ford fuel pump. Both the lit. and the pump it self says 95 PSI max also 34 gph free flow rate.If I run 5/16" return line, will this be large enough to handle the volume? Also, my fuel lines will be a combination of OE steel line and EFI rated rubber hose. Does the return line in my setup need to be rated for the higher fuel pressure? Just don't want to spend extra money if its not needed.

Also, I am using the entire harness from a 90 burb for my 86 crew cab. I want to remove the RWAL system but would like to do something a little cleaner than just leaving it unplugged. Does anyone have pin out for the EBCM? I would like to remove what wires going to the EBCM I can from the under hood harness completely, but not blindly. I know some of the wires functions, input from the DRAC, brake light output etc., but I can't find a diagram online for the others.

[rfmaster]

I guess there I'll have to tackle this question.

The Master E2000 pump is a high pressure pump - used in 3 bar systems (45 PSI) - TPI for example. It is a bit on high side for TBI which really needs 30 PSI pump. The 95 PSI rating is a deadhead rating (0gph flow) as pump flow rate will vary vs. pressure. Long story short - it is OK, but there are better pumps out there for TBI application. So, at 15 PSI this pump will deliver around 43 GPH. Example of fuel flow rate chart




The 5/16" return line is a standard size line in OE TBI. Should work just fine. Use 3/8" or -6AN size for feed.

In the engine bay ECM harness does not include RWAL except for DRAC I/O. I would use ECM harness by itself which for the most part stays on passenger side of the engine bay. There are handful of wires that cross over toward driver side of the engine bay. The rest of it I would keep OE from '86. I do not know if that is the answer that's you were looking for.

//RF

[dropd80s]

RF,
Any advice on if I need the higher pressure rated hose for the return? I suppose I will as the pressure being bled off the regulator will be significant given the extra pressure my pump will generate. Thoughts?

Also, I managed to trace out the RWAL wires and remove them. The 86 I have came with no harness what so ever, so I had to swap the entire harness from the 90 burb. No major hassle. With the exception of the RWAL system I wanted to remove, which was no big deal, it was very easy. I think it was much more simple and much cleaner to swap the entire harness than to try and separate one harness and piggy back it onto another.

Thanks for your help. This thread has answered a lot of questions.

[rfmaster]

Originally Posted by dropd80s

RF,
Any advice on if I need the higher pressure rated hose for the return? I suppose I will as the pressure being bled off the regulator will be significant given the extra pressure my pump will generate. Thoughts?

Also, I managed to trace out the RWAL wires and remove them. The 86 I have came with no harness what so ever, so I had to swap the entire harness from the 90 burb. No major hassle. With the exception of the RWAL system I wanted to remove, which was no big deal, it was very easy. I think it was much more simple and much cleaner to swap the entire harness than to try and separate one harness and piggy back it onto another.

Thanks for your help. This thread has answered a lot of questions.

Return line is a low pressure unless there is a restriction that should not be there!. I use SAE30R7 (50 PSI rated fuel rated hose) in my return lines. For the most part you want use hardline (5/16 or 3/8" ID) for 90% of the run. Use rubber hose sparingly as it will age over time and will require eventual replacement.

Yes, harness dressing can be a load of fun!

Get it done.

//RF

[dropd80s]

Ok good to know. I am using what steel fuel line I can from the burb. I would say 80-85% of the lines will be OE steel. There will just be a short line from the burb lines to the pump and the pump to saddle tank. Thanks again for your help!

[BigBlocksRule]

Yet another newbie...
I have an '85 dually that I want to sell the engine and tranny out of and install a freshly rebuilt Gen 6 454 along with a 4L80E. I have a '95 that I'm using the cab and other parts for a different project, so I can strip the computer and harness out of it, this truck originally had a 350 and 4L80E. I have access to an '87 truck that I can snag a baffled TBI tank from and plan to install a transfer pump to move fuel from the unused tank into the one with the TBI fuel pump. I also have sourced a set of gauges from a '91 so I can use the electronic speedo.
What am I overlooking?

[rfmaster]

Originally Posted by BigBlocksRule

Yet another newbie...
I have an '85 dually that I want to sell the engine and tranny out of and install a freshly rebuilt Gen 6 454 along with a 4L80E. I have a '95 that I'm using the cab and other parts for a different project, so I can strip the computer and harness out of it, this truck originally had a 350 and 4L80E. I have access to an '87 truck that I can snag a baffled TBI tank from and plan to install a transfer pump to move fuel from the unused tank into the one with the TBI fuel pump. I also have sourced a set of gauges from a '91 so I can use the electronic speedo.
What am I overlooking?

Welcome to the thread.

Donor drive train: 95 ( 2wd?) 454 + 4L80E (rear end ratio + tire size)
Recipient platform: Dually 85 (2wd?) (rear end ratio + tire size)

The 85 did not have 4L80E as OE - probably 350-700R4, 350 -350C or 350 -THM400 . You must keep the 454 + 4L80E + PCM as a unit to make swap simple. Make sure to take DRAC or VSB module from 95 donor as well. Take a look at VSS it should be where the old speedometer cable used to bolt into trany tail shaft.

I am not familiar with 91 speedometer - being electronic then it will take one of the DRAC outputs (4000 ppm) to drive it. Depending on rear end gear ratio/tire combination DRAC reprogramming maybe required to get speedometer indicate correct speed.

Late 454 TBI systems - 94 & 95 model years used higher fuel pressure over traditional 9-13 PSI used by SBC and earlier BBC TBI. Starting in '94 the 454 TBI fuel systems went from 9-13psi spec to 26-32psi. Use TPI or Vortec spec fuel pump in the 87 baffled tank:
AC Delco#: EP241
GM#: 25116163

Feed fuel line from the gas tank to the TB inlet should be 3/8" - use steel line with SAE 30R9J rated flexible lines. Original fuel line might be marginal due to its age (it was not designed for high fuel pressure operation - carburetor fuel pump operated in lift mode)

//RF

[Chad77]

OK so I have my TBI all hooked up including the O2 and I have found out that the 350 TBI injectors are to big for my 283 so Iam looking for 305 injectors GM5235279*RPD Id even take a set from a 4.3L GM 5235203*RPD. I have a set of working 350 TBI injectors Id trade! The only thing Iam not 100% positive on the #.

[BigBlocksRule]

Both are 2WD trucks.
All I pulled so far from the '95 was the engine, all the harness, etc. is still there. Fluid was dirty in the tranny but with less than 150K on the odometer, I'm going to flush it, swap the filter and run it. I have a second one from a '96 that I can use if needed, but since it's Vortec, I'm guessing I may have to swap an internal wiring harness?
I have two 454TBI's, will rebuild the best looking one of the two. I stripped an '88 with a 454 in it, snagged that TBI unit and wiring harness so I'll have plenty of wire ends, etc. but the computer is ECM, not PCM, so it'll be off to ebay with that one.
I'll probably go with something like a Holley Strip Dominator, single plane, since I'm swapping to late 60's closed chamber heads. Stock valve sizes, bowl cleanup ,etc., nothing major, I don't want to kill torque. I did manage to save the fuel pump assembly...but my TBI units are older, should I go with higher or lower fuel pressure pumps since my TBI units are older?

[rfmaster]

Sounds like you have this project under control.

Holley Strip dominator is not a good choice for TBI. TBI needs fully heated intake manifold - strip dominator is a cold intake due to its runner design. With cold ambient temperatures this intake will cause acceleration lean outs - stumbles during acceleration. Unfortunately, truck PCM does not have IAS which can be used to compensate for colder ambient temperatures.

You can use either 88 or 95 TB - just keep in mind that TPS connector is different between the two and FPR spring in 95 should be stiffer - to support higher fuel pressure. Also, the 95 TB internal fuel passages are slightly larger providing less restriction to fuel flow.

//RF

[BigBlocksRule]

Thanks for the info. I guess I've been reading too much at the 454SS site, they're more concerned with outright performance than towing. I'll find a good heated intake and go from there.
I appreciate your help, will probably need more, but that's what's great about the net - keeps us from all making the same mistakes!

[68 TT]

Originally Posted by BigBlocksRule

Thanks for the info. I guess I've been reading too much at the 454SS site, they're more concerned with outright performance than towing. I'll find a good heated intake and go from there.
I appreciate your help, will probably need more, but that's what's great about the net - keeps us from all making the same mistakes!

If you are actually going to tow with this truck then the stock small port heads and intake will work pretty well for you, probably better than the passenger car large oval port heads will. It will save you a bunch of work too as the stock tune in the PCM will be much closer to right. The VE of the passenger car heads are far different than the peanut port truck heads and will take a bunch of tuning time to get the engine to run right with them and a different intake too. Throw in a cam change and you are pretty much starting from scratch tune wise with no factory tune available to borrow from or build upon that used the bigger port heads.

I say get the thing on the road with the stock heads, intake & cam to get the bugs worked out of the swap first. Too many variables all at once will make your swap a nightmare to get running right.

After it is on the road and running right if you feel it doesn't make the power you want then tear into it and do a cam change and upgrade the exhaust. The small port heads can do pretty well. They might surprise you with a good cam upgrade, headers and dual exhaust. If it is still not making the power you want then do the head & intake upgrade.

The big valve converted passenger car oval port heads are great and I run them on my street cars instead of rectangular port heads but for a tow rig the stock small port heads may be a better fit for you.