Tbi swap build thread

[rfmaster]

Originally Posted by lahnen

yes i plan on using the th350 that i have in the truck already. original plan was to use tbi 350 but to convert it to carb, but figured at $4 gal a few more mpg would be nice seeing this is a one ton dump truck. also with the dump bed i dont think i will have a problem using the 89 tank.

Yes, indeed at $4.50 /G here in LA-land we can ill afford carbs today. It should be a straight forward swap. The bigest challenge will be cutting 2" diameter hole in the firewall and running new fuel lines (use new 3/8" soft steel fuel line) for supply.

Your 1 ton probably has 14 bolt FF with 4.11 gears. Depending on tire size your highway engine RPM is between 2500 and 3000 RPM.

//RF

[Chad77]

Hey RF when holding the injector and looking at the top and you have the long part # then you have the small # what does the small # mean? I have two injectors given to me and they both have GM5235279*RPD but the small # read D017 GM* the other Looks like N307 GM*

[rfmaster]

Originally Posted by Chad77

Hey RF when holding the injector and looking at the top and you have the long part # then you have the small # what does the small # mean? I have two injectors given to me and they both have GM5235279*RPD but the small # read D017 GM* the other Looks like N307 GM*

The small number is date code. D 01 7 can be decoded as April 01 1987 using traditional GM date coding scheme. The N 30 7 can be decoded as Dec 30, 1987. GM used to avoid using letters I and J as they can be easily confused with number 1.

5235279 is a 61 lb-hr (@13 PSI) injector, RPD stands for Rochester Products Division.

//RF

[Chad77]

Originally Posted by rfmaster

The small number is date code. D 01 7 can be decoded as April 01 1987 using traditional GM date coding scheme. The N 30 7 can be decoded as Dec 30, 1987. GM used to avoid using letters I and J as they can be easily confused with number 1.

5235279 is a 61 lb-hr (@13 PSI) injector, RPD stands for Rochester Products Division.

//RF

This the injector #GM5235206 *HPD Is what I pulled out of the TBI and replaced it with the one above and it seam to run a little better it was not loading up as much although I do have to put the pedal to the floor in order for it to start. How do I adjust for a low idle if I dont have a adjustable tps ? How much of a difference would I see with the air breather on I ask this because I dont have one at the moment ?

[rfmaster]

Originally Posted by Chad77

This the injector #GM5235206 *HPD Is what I pulled out of the TBI and replaced it with the one above and it seam to run a little better it was not loading up as much although I do have to put the pedal to the floor in order for it to start. How do I adjust for a low idle if I dont have a adjustable tps ? How much of a difference would I see with the air breather on I ask this because I dont have one at the moment ?

1) Air breather should not affect idle.

2) The reason why you need to floor gas pedal on start up is that remaining 5.7 L injector is dumping too much fuel. You need to have both injectors to be RPD 5235206 (aka 55 lb-hr). Even with both injectors being 55 lb-hr your tiny 283 will run rich on start up! Having O2 will help ECM to lean out fuel mixture. Additional EPROM changes would be required (later on) to optimize VE table.

3) You need to verify that your idle air control motor is working. The way you do this is by inserting a jumper wire between pins A & B of ALDL connector (do you know what it looks like?). ECM will command IAC into fully closed position. Do not start engine - just turn ignition into run - you should hear clicking noise coming from TB. Clicking noise is from IAC motor jamming pentacle head - keeping idle air passage closed. Remove harness connector from IAC (4-pin square), turn off ignition. With Ignition off reconnect IAC motor connector. Now ECM knows fully closed position. This way it will be able to control idle speed by controlling amount of idle air.

//RF

[Chad77]

So If I get a set of injectors from a 4.3L I should be set as for gas amount?

[rfmaster]

Originally Posted by Chad77

So If I get a set of injectors from a 4.3L I should be set as for gas amount?

You'll be better off with 55 lb-hr injectors from 305 (5.0L).

The 4.3L V6 injectors are only rated for 45 lb-hr and can support 170 vs. 208HP offered by 55 lb-hr units. Another reason why you want to use 55 lb-hr injectors is that BPC calibration constant used in 305 calibrations is 132 (please post your ECM service number and broadcast code). When BPC constant is calculated for 283 with 55 lb-Hr injectors BPC is 122. 10 points is not bad (it is not great either and eventually you would want to have a custom EPROM burned). If you use 45 lb-Hr injectors for your 283 then BPC constant is 149 - 25 points of. With 45's you'll always start on lean side and with 55's you'll be slightly rich. Stock 283 heads (we are talking 40+ year old designs) are not known for high efficiency combustion chambers and like to run slightly on a rich side anyway.

Why is it important? ECM has no idea if injectors have been changed to a different size or engine displacement is different. It calculates amount of fuel based on EPROM stored values. O2 provides some degree of trim over stored baseline line values. Change one or more variables - the amount of fuel commanded will be of from what engine needs for best performance.

All TBI injector ratings are baselined at 13 PSI.

//RF

[Chad77]

RF I am not finding any info on this question. I have a chance to pick up a 1970 350 4 bolt main with 17000 on rebuild.

The question is could I pull the 70's intake off and and put the TBI intake on or could I just put the tbi on the 70's intake with the adapter ?

[Chad77]

O one other question other then the intake what is the deference from a tbi to a LT1 engine could I swap out the intake?

[Jonboy]

Originally Posted by Chad77

O one other question other then the intake what is the deference from a tbi to a LT1 engine could I swap out the intake?

Gen 2 SBC is a whole other animal. The engine is reverse cooled, does not use a traditional distributor, the water pump and opti spark are driven off of the cam gears, etc.

Originally Posted by Chad77

RF I am not finding any info on this question. I have a chance to pick up a 1970 350 4 bolt main with 17000 on rebuild.

The question is could I pull the 70's intake off and and put the TBI intake on or could I just put the tbi on the 70's intake with the adapter ?

Yes, you can just use an adapter.

Originally Posted by rfmaster

Do you have a mechanical speedometer in your '86. If you do then you can simply insert 2PRS (2000ppm) VSS inline with speedometer cable. Connect one wire to ECM and one to the ground - done. (assuming that you are keeping 86 4x4 trany and x-case and putting 89 350 in place of tired OE)

I do not know what exactly harness from fuel injection connection has (it is probably custom build to order). Generally speaking EFI harness is a stand alone system - only a handful of connections to the fuse box and P/N switch (and brake switch for TS control).

If 89 tanks fits - use it, but make sure to replace rubber hoses with EFI rated SAE 30R9 fuel hoses.

//RF

The fuel injection connection harness was very similar to the Painless stand alone harness, except in price. Seems like there were less than 10 wires total to hook up.

[Chad77]

Originally Posted by Jonboy

Gen 2 SBC is a whole other animal. The engine is reverse cooled, does not use a traditional distributor, the water pump and opti spark are driven off of the cam gears, etc.
.

Really ? The 89 LT1 out of a Iroc-z that I have setting in my garage has the same dist as the TBI set up.


O thanks

[rfmaster]

Originally Posted by Chad77

Really ? The 89 LT1 out of a Iroc-z that I have setting in my garage has the same dist as the TBI set up.


O thanks

LT1 was first introduced in 92 Corvette and in 93 in a fourth gen Camaro. It is a popular swap to drop an LT1 into a third gen Camaro. Gen II (LT1) shares the same rotating assembly (crank shaft, pistons, connecting rods, and flywheel/flexplate) and some of valvetrain parts. Bell housing bolt pattern is same as before. However the LT used a new engine block, cylinder head, timing cover, water pump, intake manifold and accessory brackets. Take a look at engine block casting number - this should positively id your 'LT1' engine.

//RF

[Jonboy]

The original engine in your '89 IROC would be an L98, if it is a 5.7. That is gen 1 SBC, with TPI (Tuned Port Injection). Physically similar to doing a TBI swap, but you will have to pay more attention to the fuel system. TPI will want 43-46 PSI, compared to 13 or so fir TBI.

[SLR_65]

Hi Guys,

Just a quick update - I found a DRAC for $20! Actually, I found two - I bought one for spare since they seem to be getting hard to find. Half price of the Dakota Digital solution and I have a spare. I love hunting parts, finding/recycling them, and saving money! We all win!

Now to get serious about hunting up a '91 Suburban speedo . . .

[68 TT]

Originally Posted by SLR_65

Hi Guys,

Just a quick update - I found a DRAC for $20! Actually, I found two - I bought one for spare since they seem to be getting hard to find. Half price of the Dakota Digital solution and I have a spare. I love hunting parts, finding/recycling them, and saving money! We all win!

Now to get serious about hunting up a '91 Suburban speedo . . .

Can be a 1990 as well and from full size Blazer too.

[SLR_65]

I've ran across a few 90/91 Suburban speedos online and many say "blue" or "blue/silver". do I take it that a blue background with silver pointer / numbers was an option? I've tried to look up what the speedo options were online, as well as tried to find a picture of a "blue" burban speedo but I can't find any info at all on 'em - can you enlighten me?

Thanks!

Steve

[68 TT]

Originally Posted by SLR_65

I've ran across a few 90/91 Suburban speedos online and many say "blue" or "blue/silver". do I take it that a blue background with silver pointer / numbers was an option? I've tried to look up what the speedo options were online, as well as tried to find a picture of a "blue" burban speedo but I can't find any info at all on 'em - can you enlighten me?

Didn't know there were different ones. This is the first I have heard about it. I would like to know the difference too.

[cheepin]

Should the A6 pin have power under cranking?

[rfmaster]

Originally Posted by cheepin

Should the A6 pin have power under cranking?

If you have 1227747 ECM Pin A6, Ignition-ECM Fuse (Pink/Black wire) must have 12.0 to 13.8 Vdc when ignition is on. Failure to have 12.0 V during cranking will shutdown ECM and injectors will never fire. Not good at all.

//RF

[cheepin]

Got it thanks!Didn't have power under cranking.

[SLR_65]

Hi Guys,

I'm hoping to start on this project the first part of June. Until then I've been gathering parts - got the DRAC problem solved by a couple of fellow forum members (thanks guys!) and I picked up an electric speedo that's supposed to be off of a '91 Suburban and it arrived today. Got a couple hundred thousand on it but that's OK, I don't care what the mileage displayed is as long as the speed displays correctly. The trip metter even still has the stem and it reset the meter back to zero so I'm assuming it works.

I wish I could find the camera but alas my wife and daughter are gone and I can't find it (I can't find stuff in the fridge either!). It has a cut mylar ribbon cable going to a connector that slides onto the speedo pcb. The ribbon cable and pcb have three leads. I'm assuming soldering to that mylar ribbon cable isn't going to happen so using the connector probably isn't an option (though I haven't taken it apart to see if it is or not yet). I'm sure that's no mountain to climb though, one could probably just solder leads onto the pcb traces where the connector slid on.

Do I take it the three leads are power, ground and signal?

Can anyone clue me in on which is which?

Thanks!

Steve

[SLR_65]

Found the camera!

Here's the electrical connector I'm talking about. It appears in this pic only two leads have traces on the pcb but the third trace is on the other side of the pcb.

/Steve

[rfmaster]

Originally Posted by SLR_65

Found the camera!

Here's the electrical connector I'm talking about. It appears in this pic only two leads have traces on the pcb but the third trace is on the other side of the pcb.

/Steve

Ahhh the joy of reverse engineering old circuits. Take look on component side of the PCB - there should be a 8 PIN DIP IC (I guess) - it is in upper right portion of PCB when viewed from the back. It should have mfg part numbers printed on it. By the looks of it, depending on IC orientation, either Pin 1 or 5 tied to trace that is also connected to the lower trace of I/O connector. Lets start there.

If there are any electrolytic caps - find negative terminal which are usually tied to chassis ground. Use DVM to find which of the three pins (if any) are ground connected by checking continuity from cap neg terminal.

//RF

[SLR_65]

Ok had a few minutes . . .

I held the speedo in it's normal position and then rotated it so I could see the back. When I do that the connector is on my left side and the three connections are as follows:

Pin 1 ===>
Pin 2 ===>
<gap>
Pin 3 ===>

When viewing the back of the speedo there is a 16 pin dip in the upper right hand side of the pcb with a paper tag and a part number printed on it. I didn't get the part # written down, though I thought I did. It has pins 1 & 5 tied together but where it goes from there I lose as it as the tracegpes under the chip.

There is another 16 pin dip chip below that, It's a Texas Instruments chip and has the following printed on it:

<TI symbol> 022 CB
AC SPARK
980 6535H

There is an 8 pin dip chip in the lower right and on top of it it says:
1681B
CS9035H
Pins 5 & 8 of it are tied together. They run to a 15K resistor and it runs to Pin 1 of the connector

Pin 2 of the connector indeed runs to the negative side of a polarized cap.

Pin 3 of the connector runs to a diode oriented like this: -->l-- and then a resistor and then I lost it.

Sooo, we have:

Pin 1 ===> 15k resistor, 8 pin dip pins 5 & 8
Pin 2 ===> negative side of polarized capacitor
<gap>
Pin 3 ===> diode -->l-- , a resistor and more.

I tried looking the chip part numbers up to see if I could get a clue as to what they do but I didn't have any luck. The 16pin dip in the upper right with the paper printed part # seems to have a crystal hooked to a couple pins if that helps.

Thanks!

Steve

[rfmaster]

Steve

AC-Delco (GM) is notorious for using custom part numbers of commonly available parts. When you buy a million of anything in electronic industry putting a custom part number is an unquestionable ritual. Makes reverse engineering just a little bit more difficult. Let me take a look at my 94 FSM see if it offers anything worth of note worthy.

//RF