[Gmecm] ? about pre-efi gm ecm

[Jared Ryan]

I converted a 1984 LG4 305 El Camino to TBI using a Painless harness 
and a 1228746 ECM.  I prefer the '746 because it uses an inlet air 
temperature sensor and can control valves for an AIR pump.  I kept the 
part numbers of what throttle and cruise control brackets work and 
other parts.  Parts from a '90 R-series Suburban with a 350 fit very 
nicely.

The 1226865 is for a CCC carburetor, one that has a TPS and a mixture 
control solenoid.  It is the ECM my El Camino had with the feedback 
carburetor.  It is much easier to remove the entire factory harness for 
the feedback emissions system and use the Painless harness.  That is 
what I did.  The factory ECM harness is accessible by unbolting and 
moving the right front inner fender.

The MAP sensor will need to be changed.  Unlike the carbureted ECM, TBI 
does not use a BARO sensor (which is under the dashboard above the 
glove box, next to the Check Engine light driver).  Instead of driving 
the Check Engine light through a driver, the EFI ECM drives it 
directly.  There are several small things like that, that will need to 
be changed.

If you are using a TBI manifold and throttle bracket, you will need the 
correct kickdown/TV cable.  Again, the part for a '90 R-series Suburban 
with a 350 fits nicely.

Inline Tube sells the fuel supply line for EFI for the El Camino.  You 
will end up installing that and using the stock fuel supply line as the 
return.  Outlets that sell restoration parts for the El Camino have the 
correct fuel tank sender that mounts an internal fuel pump, which is 
very helpful, unless you want to use an external pump.

I remember almost everything about the conversion, but it is better to 
ask specific questions about the conversion to help jog my memory.  I 
will help as best I can.

I will take some pictures of the engine compartment in its current 
state and put them on my Web site.  The serpentine belt system and 
Camaro air cleaner (moves the snorkel to the driver side, much better 
fit with serpentine belts) make it look a little different, but 
hopefully it will help and it will show how neatly this conversion can 
be done.  Those who are not familiar with this body style do not 
realize the significance of what they are looking at.

1984 Chevrolet El Camino
GM Goodwrench long block 350
Crane PowerMax 2032 hydraulic roller cam
Edelbrock 3704 intake manifold
GM serpentine belt conversion
TBI fuel injection
TH-200-4R automatic overdrive
3.23:1 rear axle with PosiTrac
Hooker AeroChamber muffler

Passes emissions inspection, 20+ mpg highway, 16 mpg in town with A/C 
on.  Not too shabby for an '80s brick.

  ---> Jared Ryan <---
jryan at caminofx.org | http://www.caminofx.org

On Aug 26, 2006, at 8:46 PM, dgilbert78 at juno.com wrote:

> Hello: My 85 elcamino had a 4.3 TBI factory. Removed the 4.3 TBI,
> installed a 350 using the same TBI with 350 injectors. Used same wiring
> harness with 1227747 ECM and chip from a 87 350 pick up. Because yours 
> is
> a carbed engine I suspect the harness will not work very well. If you
> have any other questions feel free to ask
> good luck
> Darryl..
> On Sat, 26 Aug 2006 18:09:25 -0700 (PDT) Rick McLeod
> <dunvegan at sbcglobal.net> writes:
>> Getting ready to launch a new project: convert 1985 ElCamino 305 4BBL
>> to EFI using TBI
>>
>> The current engine uses a 1226865 ECM to control the engine ?? which
>> is appears to be a vacuum control carburetor? I am not finding any
>> reference to information regarding this ECM. I'm sure others have
>> done this conversion, but here's my draft plan. If anyone has done
>> this conversion, can they chime in w/ thier comments, please?
>>
>> Use an ECM such as the 747 and a suitable bin, Painless harness, and
>> the throttle body that 'matches' the bin/ECM chosen. Obviously, will
>> need to ensure the sensors match, but this engine already has some
>> in that it is an ECM engine w/ O2, so I assume (dangerously) that it
>> has coolant, manifold pressure, knock (maybe) already that are
>> suitable.
>>
>> I'm open to suggestions and guidance to kick start me in selections,
>> unfortuantely most all my experience is w/ the 165 on TPI L98's.
>>
>> Thanks in advance for suggestions.
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