Re: Tbi swap build thread
 

Instead of finding a DRAC you can get a Dakota Digital product that performs the same functions. It is about $75 at Sumit Racing.

Re: Tbi swap build thread
 

Well crap! I just swung by my favorite salvage yard. This is a neat old place, I used to go there as a kid with my Dad (and my sons and I just toured it a couple years ago!) and it has cars going back for decades. Has a few rows of 30's/40s/50's era cars and even an old Liberty truck that's been there for as long as I can remember.

Well, it DID anyway! Today I'm greeted by the sound of a crusher running and the field with the really old stuff was empty! They are crushing most older stuff. The really old stuff and the camaros, mustangs, etc. all got sold to an outfit in Oklahoma and they picked them up a few weeks ago!

They aren't closing, they are just starting over. They had no demand for their old stuff so they are scrapping it and focusing on stuff that's about 10 years old or newer.

He didn't have any early '90s stuff any more at all so I didn't get a DRAC. He knew exactly what I wanted and said it would've ran $10, but they crushed those vehicles a week or two ago!

It's truly a sad day here in Steveville!

We have one more salvage yard in town but they've been more of a crush yard than anything for a long time now so I'm not holding out much hope.

About 20 miles south of me is a yard that specilizes in older stuff so hopefully they'll be able to help me.

I'm aware of the Dakota Digital device and may end up using it, but I have a question about it that I'll have to ask them first . . . it only has one 2,000 PPM output and I need two, one for the computer and one for the speedometer. Is it OK to split that line and feed both? On the original DRACs they had two separate outputs for those signals. Even if you can't I'm sure you could use one of the other lines and little more circuitry to divide down what you need, but the original OEM DRACS appear to be very reliable, easily modified with dip switches so you can configure them for new gear ratios and tire sizes, and if you can find one they seem to be CHEAP! It's hard to beat that combination!

A friend of mine is an elctron guru too and I mentioned this to him and he got a twinkle in his eye and started mumbling about pic chips and stuff. Later he wanted to know how many pulses per revolution and my gear ratio and tire size so I'm sure he's cooking something up too so I'll probably have another option. 8->

I'm having trouble finding stumbling blocks / reasons NOT to do this project, so it looks like it's time to order some parts and start stripping the donor truck!

TTYL,

Steve

Re: Tbi swap build thread
 

read through alot of pages, answered some questions, still unsure on some others. i have a 86 k30 4x4. going to put in a 89 350. will a harness from fuelinjection connection be able eliminate any not needed things, such as the speedo issues im reading about. i would like to just to use the original speedo cable and not have to swap out clusters. originally i planned on trying to use the 89 wiring, computer, and what not, or finding a 87 harness with out buying another truck for parts, but if i can buy a harness that just needs to be plugged in, i'd rather do that route. if theres anything else i'm over looking or left please let me know. i'm also gonna use the new gas tank from the 89 seeing how it has a new sending unit and pump

Re: Tbi swap build thread
 

I'm still researching my swap so don't take the following as gospel . . .

*) The wiring harness would provide just what you need to run the fuel injection without having to deal with a 20 year old harness and wiring for other circuits. They can come stock or with the EGR and AIR injection removed. Personally I'm not a proponent of removing the smog equipment - in this day and age I don't think any of us are too far away from local municipalities invoking smog laws and requiring inspections and it can be expensive to replace the smog equipment if you toss it. At the least I'd leave it physically on the vehicle and just disable it.

*) What your speedo options are I think will depend upon what vehicle your 89 350 came from. If it had rear wheel anti-lock brakes then it will have the 40 pulse per driveshaft rotation vss in it like my donor did (all 89 full sized trucks came with abs) and that makes the speedo a little harder to deal with. Jags That Run have some methods to deal with it if you don't want to change the speedo. If the donor didn't have the antilock brakes though then you should still have the speedo drive gears in the tail of the tranny and there are several options to provide for cable driven speedo and provide a vss signal for the computer.

*) I'm not sure an 89 gas tank will fit into an 86 truck. If it will then I'll save myself a few bucks and use mine too!

*) If the tank wont work at least the fuel sending and pump will according to the LMC truck catalog anyway.

Hope that helps!

Steve

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

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.

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

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*

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

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 ?

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

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 ?

Re: Tbi swap build thread
 

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?

Re: Tbi swap build thread
 

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.

Yes, you can just use an adapter.

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.

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

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.

Re: Tbi swap build thread
 

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 . . .

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

Should the A6 pin have power under cranking?

Re: Tbi swap build thread
 

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