Re: Tbi swap build thread
 

VSS is still used today to provide data to the PCM/ECM for engine controls, speedo, cruise, trans shifting scheduling, torque converter lockup, etc but not ABS. These days, there is actually a wheel speed sensor at each wheel to provide input to the ABS module to control 4 wheel ABS system and traction control if equipped. In the TBI days the trucks only had rear wheel ABS which the rear wheel speed input to the ABS module was read from the VSS sensor on the tail shaft of the transmission.

Re: Tbi swap build thread
 

my bad

Re: Tbi swap build thread
 

My apologies - 7747 does not have DFCO - MPH threshold, which is used in 8746 ECM found in TBI passenger cars. Also, DE is mapped to MAP and RPM threshold in 8746.

Now that I looked back at my notes I know where I got confused - in my conversion I used 16136965 from 1991 B-Body which just happens to be almost pin compatible with 1227747 (there are couple more control outputs and MAT input) which in its stock form uses speed threshold for DFCO. In the end it did not matter to me at all since I have converted to EBL which provides full control over DE and DFCO.

VSS in 7747 is used primarily for TCC control, Knock retard, Highway SA, EGR, & Idle speed compensation.


//RF

Re: Tbi swap build thread
 

This thread is turning out to be what I wanted, A bunch of info on this swap that you don't have to hunt and hunt for on the net at a ton of different sites.

Keep the info comming. Please share what you have done and if you have a question, please ask it.

I am going to have some more progress pics on my swap tomarrow so stay tune.:burnout:

Re: Tbi swap build thread
 

Rf,

Don’t worry, it easy to get confused with all this EFI stuff as there is a lot of information out there with different operation systems. Every time I think I just about got it all figured out….you learn something new.

Re: Tbi swap build thread
 

So, rf & Dirty Larry, is there any benefit to installing a VSS in my ride? As mentioned above, it is an 89 setup, so there is no DRAC in this setup. I'm still using the mech speedo and have no cruise. THANKS FOR YOUR HELP!

Re: Tbi swap build thread
 

What did you find out on your truck about the wiring?

Re: Tbi swap build thread
 

cj- I haven't had a chance to look at it yet. I'm gonna have to spend some time this weekend tracing it out. When this swap was done, I paid a GM technician in beer after hours to hook it up for me so I have limited knowledge on the details of the system. Is there something in particular you want info on? The dash is currently apart because I am just finishing off a frame off restoration, so it would be easy to trace out what was done. LMK

Re: Tbi swap build thread
 

Nothing really I was wondering if the vss is acctually hooked up or not.

Re: Tbi swap build thread
 

The VSS is not hooked up. I have the wire ready but I still need to buy a VSS which will give an electronic signal from a mechanical speedo drive. I would still like to know if this is necessary. I'm kinda waiting on rf or DirtyLarry to see what they say.

Re: Tbi swap build thread
 

Well on a auto trans I am sure you will need it, but on a 4 speed I do not know.

Re: Tbi swap build thread
 

Skidder,

I would venture to say you are good to go without VSS on a manual transmission. With an automatic, yes, you would need it for the torque converter lockup. Your earlier post mentioned a concern with going into closed loop. Closed loop is achieved by the engine coolant temperature sensor (ECT) and O2 sensor inputs not vehicle speed.

My 8.1L with a manual trans does not have a VSS at all. Even though the 8.1L is multiport EFI, mine is running an OBD I speed density calibration system through a Marine MEFI-4 engine controller with a protocol that is very similar to the old TBI and TPI systems of the late 80’s and early 90’s. As far as fuel delivery, the main difference is my 8.1L fires 8 injectors under a higher fuel pressure in batches where as TBI is firing 2 at a lower fuel pressure. Firing the 8 individual coil packs on the 8.1L is what is unique about the MEFI-4 controllers as they are very versatile in programming what they can control….but that is a whole nuther story.

This is one of the reasons I have chose to go with aftermarket harnesses opposed to reworking a donor vehicle harness. First, a donor vehicle TBI harnesses are getting old (last TBI truck was built 15 years ago!) and the harnesses tend to be very brittle and stiff, end connector break at the touch, etc. Second, a creditable aftermarket harness vendor such as Howell or Street and Performance, etc has already put a lot of research into knowing how to properly wire these things. Most of those companies have gone to the manufactures and purchased the original engineering layout drawings to create stand alone harnesses without all the unnecessary circuitry. For $325 a nice fresh harness is hard to beat vs. pulling your hair out trying to rework an old harness only to still have a 15+ year old harness when you are done.

Re: Tbi swap build thread
 

Dirty Larry- Thanks a million! This swap was actually done about 12 years ago. I drove it for a couple years then tore it down for restoration so it has been sitting for a while. The wiring is in nice condition, but if problems ever start, I will look at updating. It is difficult to make the '89 wiring look like it is supposed to be there tho. I am going to check on that p/n wire and try your suggestion. Once again, THANKS!

Re: Tbi swap build thread
 

Larry you have a very good point about the old harness on the fact that it is old and the wires are brittle, (mine has been for the most part very managable though) and me and you talked about me buying a harness from Howell. I am right now off work untill the first of the year and I want to get this swap done before I go back to work. Untill I go back to work I really do not need to spend any more money than I have to. So I had the stock harness and decitted to use it. When I decited to do that I thougt while I was searching the net for info on this swap that the info is out there but you really have to look every where for it. So I decited to start this build thread to maybe help other people out that want to do this swap and use salvage parts in the process to save a buck or two.

I really do appreciate the input that people are putting in this thread ( like you and rf).

Got to go and work on my truck now.;)

Re: Tbi swap build thread
 

Well I did not get to work on it as much as I wanted to to day but did get a little done.

First two is a before and after on one side of the motor. This is where the ESC, TPS, MAP, IAC, EGR , and temp plugs are located. You can also see where the wires enter the cab

The others are the wires that I will have to hook up in the cab. They are

B-10 park/neutral
A-5 SES light
A-8 ALDL
A-9 ALDL

Re: Tbi swap build thread
 

Here are some of the wires that I will have to hook up that do not have factory plugs.

The first one turned out fuzzy but it is the 12 V feed wire (I am going to put it to the big post on the starter with a inline fuse).

The second is C-9 this wire goes to the sm post on the stater.

The Third is the switched 12 volt wire. ( I am going to put it on the smaller wire that pluged into the orginal HEI BAT terminal).

The Foruth is the ground wire for the system.

The Fifth pic is the wire that will power the dist. ( I am going to tie it to the big HEI wire that is on the truck now.

Re: Tbi swap build thread
 

Gents

VSS is important as it is not only used for the lock-up torque converter control. The VSS is also used to control the EGR valve, idle speed, and air/fuel ratio. I have to emphasize that the VSS is used to control the idle speed when the vehicle is moving. Without the VSS, engine may have stalling problems under certain conditions, which in itself is dangerous. You can increase minimum idle speed with the adjusting screw and eliminate stalling, but the engine will still not run optimally without a VSS.
Somewhat erroneously many think that running "closed loop" is best for fuel mileage - it is not. In closed loop NBO sensor is being used to monitor the exhaust O2 content and ECM changes commanded AFR. There are ECM's that allow engine to run very lean (15:1 to 17:1) under certain conditions (called "highway lean mode") to improve fuel mileage during - for example steady cruise conditions (no delta TPS, no delta MAP). Without VSS, ECM will not get the correct signals to run the engine for best fuel mileage. So if you are planning to drive long distances and burn less fuel VSS is a must. For my retrofit I used JTR Part #2PRS which is two-pulse per revolution, square wave unit for all TBI installations, 7/8-18 thread, .104" square drive. BTW, I get 17.5 MPG on extended cruises (that's 6500lbs moving at 65 MPH).

//RF

Re: Tbi swap build thread
 

Photos from my swap

It all started innocently enough in the fall of 06 - another tune-up and idle quality and cold starts are hideous with old Q-jet. After a bit of reading I came across a TBI 4.3 swap into a Jeep...
http://www.bustedjeep.com/projects/junkyardtbi.asp

After reading and a quick trip to a local pull it your self JY


ECM / Harness /Dizzy (useless) / sensors
http://i226.photobucket.com/albums/d...re031-crop.jpg

It took over 2 hours at JY to carefully pull this tangled mess without breaking anything in the process. The firewall grommet in this B body used epoxy like filler to keep everything together - nasty to remove.
http://i226.photobucket.com/albums/d...Picture033.jpg

After another 2 hours the harness was hanged like a deer for cleaning.

http://i226.photobucket.com/albums/d...cture040-r.jpg

Removed wires and vacuum lines used by AC control circuits

http://i226.photobucket.com/albums/d...Picture042.jpg

Final harness, arranged and labeled
http://i226.photobucket.com/albums/d...to056-crop.jpg

Surprisingly enough wires were in excellent shape - no breaks this was a low millage car. I did had to replaced several connectors - broken tabs and shorter overall runs. However in my next conversion I will get new harness - just to save time! Initial harness fitting:

http://i226.photobucket.com/albums/d...to117-crop.jpg

Re: Tbi swap build thread
 

Im in the middle of this very swap keep the info comming. I removed and inline 250 and I putting a 5.7 and 4l60 out of a 92 van. So thanks for the info.

Re: Tbi swap build thread
 

I used a donor 1990 G-van a while back for the powertrain as well. Vans are great sources of parts. Link below.

http://67-72chevytrucks.com/vboard/s...d.php?t=306106

Re: Tbi swap build thread
 

I know I cant use the towers out of the van can I use the towers off of the inline 6 (250)?

Re: Tbi swap build thread
 

Update in a few days is comming if I do not get any more service calls.

IT has been cold here of late and no heat calls have keep me busy.:metal:

What are you calling a tower?

Re: Tbi swap build thread
 

hvac tech are we?
i have been working in the hvac industry for 5yrs..

Re: Tbi swap build thread
 

The 6 cylinder engine mount towers in your ’70 C10 will not work. If you plan on using the G-van or any of the newer style exhaust manifolds you will need either 67-72 big block towers or use 73-87 2wd towers like I did on my ’72.

Re: Tbi swap build thread
 

Yes sir been in the service feild going on nine years now. Mostly comercial refrigeration, but I do residential:metal: on the side.