[Gmecm] ? about pre-efi gm ecm

Sun Aug 27 15:30:00 UTC 2006

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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