[Gmecm] ? about pre-efi gm ecm

Sun Aug 27 19:54:21 UTC 2006

The biggest problem in changing the intake manifold is the spacing of  
the four bolt holes near the carburetor/TBI pad.

Beginning with the 1987 model year, GM changed the angle of these  
bolts, to make it easier to get a wrench on them.  They are at a  
different angle from the other eight bolts.  I ended up drilling them  
out with a drill press to make a GM TBI manifold fit on an '84 engine.   
When I replaced the 305, I got a new long block that had the '87-later  
bolt angle and used an Edelbrock 3704 manifold.

Don't worry about the thermostat or anything like that if changing  
manifolds.  It is in the same place.  The ECM coolant temperature  
sensor will screw into the manifold instead of the thermostat housing,  
or you can put a pipe plug in the manifold and leave it in the  
thermostat housing.  The heater hose will go to an outlet at the back  
of the manifold instead of the front.  None of this is a big deal and  
it basically falls into place.

The biggest issue is the linkage.  Instead of hacking something up, I  
got the brackets and TV cable from a TBI Suburban.

You will need to run a new supply line to the fuel tank.  It must be  
3/8" diameter.  The stock line is 5/16" and it will work as the return  
line.  The vapor line will keep its current job.

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

On Aug 27, 2006, at 12:36 PM, Rick McLeod wrote:

> Painless shows a sweet little adapter that looks to solve the TBI  
> retrofit to non-TBI manifold bolt pattern problem:
>
> http://www.painlessperformance.com/assets/pdf_catalog/06Catalog_pg26 
> -27.pdf and the part # is PPP-60118 which Summit shows for about $93  
> and change. If this is workable, it would greatly solve some problems,  
> one could quickly run up nearly that much money if cracking the valley  
> open to swap the manifold, in that you also then need to address  
> thermostat/outlet matching hose to radiator, and a host of other  
> plumbing issues. Hence my reasoning to not change the manifold if  
> possible.
> Any one have experience/thoughts on this part of the quest?
>
>
> ----- Original Message ----
> From: dgilbert78 at juno.com
> To: dunvegan at sbcglobal.net; gmecm at diy-efi.org
> Sent: Sunday, August 27, 2006 10:30:00 AM
> Subject: Re: [Gmecm] ? about pre-efi gm ecm
>
>
> Hello: The bolt pattern for a TBI is quiet a bit different than carb  
> bolt
> pattern. I know 4.3 and 350 use same TBI unit with the exception of
> injectors. The 4.3 is basically a short 350 if you want to look at it
> that way. Even the knock sensors are the same. I think All TBI  
> manifolds
> will need the 4 center bolt holes machined or adapted because of the
> different angle of the 4 center bolt holes (2 on either side )
> Good Luck with your change over.
> Darryl..
> On Sun, 27 Aug 2006 07:42:03 -0700 (PDT) Rick McLeod
> <dunvegan at sbcglobal.net> writes:
>> My objective is simply to get this vehicle to EFI with absolutely as
>> little modifications as possible. I was under the impression GM's
>> initial TBI was essentially the next step in evolution from carb to
>> EFI, transitioning through the CCC (short lived) phase, so a couple
>> questions come to mind:
>> Will the throttle body for a TBI directly replace the CCC carb, or
>> is it absolutely necessary to lift the manifold and replace it?
>> If I can use the existing manifold, shouldn't all the linkage and
>> kickdown cables essintially just hook up,
>> We've a local show and swap event next weekend, so I'd like to have
>> a 'shopping list' in my pocket of things to try to find. With that
>> in mind, will the 846 work w/ most any GM throttle body from an
>> equivalent engine, ie from a truck w/ 305 or can I expand my search
>> to include throttle body units from the 350 as well.
>>
>> Jared, your comments are going a long way toward getting me started.
>> I'd hope you can either place a link on the twiki or even some of
>> the write up papers as well, so we capture this. I intend to try to
>> photo-doc this conversion, I didn't do that on the last one and am
>> shooting my self. ('83 Jag lumped w/ an '89 IROC Z/28 TPI)
>>
>> Again, thanks for the comments from all so far, I hope to keep this
>> alive long enough to come up w/ my menu and plan.
>>
>>
>> ----- Original Message ----
>> From: Jared Ryan <jryan at caminofx.org>
>> To: gmecm at diy-efi.org
>> Sent: Sunday, August 27, 2006 2:21:15 AM
>> Subject: Re: [Gmecm] ? about pre-efi gm ecm
>>
>>
>> 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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>>>>
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>>
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