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Holley 4 barrel TBI with GM ECM

eagle mark

eagle mark

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Looking for some information on getting a Holley four barrel TBI running on a GM TBI system.

First problem I see is in reading the Holley manual the front two injectors need to run at idle and low RPM with rear injectors off. I have no idea how to do this with a 1227747 type ECM or if it's possible.

Or can I run all injectors? Right now they are firing right front left rear, left front right rear. Holley manual states the front two have to fire at idle and low rpm or it will not run properly.

System is on a built 440 Mopar engine and the system was bought aftermarket but has never run. Chip was nothing more than stock 454 TBI. I can burn chips and tune the engine once running but wondering if anyone has had a four barrel Holley TBI experience and noticed if the injectors are all firing at the same time. I guess there is a progressive linkage and a simultaneous linkage. Seems the Holley ECM has adjustments for this.
 
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Thought i read somewhere that the 7747 ECM cannot support driving more than 2 injectors.
 
Not sure. I have seen a twin TBI on a 409 dual quad intake run on the 7747 but it may have had only one injector on each TBI fireing...

dualTBI.jpg
 
GM did run some dual TBI's on firebird or camaros but stopped doing it because it didn't work as well as thought. You might check into what ECM was used with those packages.
 
corvette crossfire injection was done. but if i recall it was 2 1 barrel units with a big injector. heard of them never realy seen one my self.
 
Yep, crossfire is what i'm talking about and they were used on firebird or camaros for a couple years. They were standard 2bbl TBI's.
 
Only ones I have seen are one barrel TBI units.

0900823d801639d5.gif
 
Damn, now you have me wondering. I may have to take a trip to the local wreckers again and see if they have any of the cars with the crossfire and check to see if it is a 1bbl.
 
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Partially because I've always wondered what was up with the Crossfire Injection setup. I know Vettes used it from '82-'84. Since it is a form of TBI, and it predates our trucks by 5 years, this has always had me wondering... When did EFI actually begin to be installed in GM vehicles?
 
jonrpick said:
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Partially because I've always wondered what was up with the Crossfire Injection setup. I know Vettes used it from '82-'84. Since it is a form of TBI, and it predates our trucks by 5 years, this has always had me wondering... When did EFI actually begin to be installed in GM vehicles?
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From my ancient reading I think the Corvette crossfire was only 1982. They did not make corvettes in 1983 but some leftover 82 were sold as 83. I think Cadillacs had some EFI around then too. This was typical of the auto industry trying to keep up to emissions with experiments like the dreaded electronic carburator... :eek1:
 
eagle mark said:
From my ancient reading I think the Corvette crossfire was only 1982. They did not make corvettes in 1983 but some leftover 82 were sold as 83. I think Cadillacs had some EFI around then too. This was typical of the auto industry trying to keep up to emissions with experiments like the dreaded electronic carburator... :eek1:
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The only true 83's were prototypes for the new C4 body style. The C4 came out so late that they skipped naming it for the '83 model year, and instead called it the 1984 Corvette.

Cross-Fire Injection (L83) did carry over into the '84 Vettes though, but switched to TPI (L98) in '85.
 
jonrpick said:
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When did EFI actually begin to be installed in GM vehicles?
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I'm pretty sure GM started installing EFI in cars around 82-83. GM was playing with mechanical fuel injection in Vettes back in the early 60's though.
 
4X4HIGH said:
I'm pretty sure GM started installing EFI in cars around 82-83. GM was playing with mechanical fuel injection in Vettes back in the early 60's though.
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GM started with mechanical fuel injection in 1957, the top rated 283 with the Rochester fuel injection was the first Chevy engine with 1 hp per cubic inch. The Rochester injected Corvette motor's last year was 1965 with a 375 hp 327.

Gus
 
Yeah, i forgot that GM installed the mechanical injection on a few 57 chevy's.
 
pauly383 said:
Cadillac Seville , 1975 , a little crude by our standards :D
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OMG!!! I remember a day course on that during my auto mechanic training in 1976 when I got out of high school... no one thought EFI would catch on then... :doah:geez we were all wishing we took electronics classes just to keep up with electronic ignition...
 
eagle mark said:
OMG!!! I remember a day course on that during my auto mechanic training in 1976 when I got out of high school... no one thought EFI would catch on then... :doah:geez we were all wishing we took electronics classes just to keep up with electronic ignition...
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I know that feeling... My high school had a vocational school right next to it. I did take a small engines class when I was a freshman. I so wish I could go back and add to that. I can't complain though. That class was honestly the starting point for me getting into car engines. Bigger and better, right? :D
 
bigblock72 said:
You can get your computer modified to run 4 injectors.http://www.dynamicefi.com/4-INJUpgrade.php
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Thanks but after some more research I don't need any more injectors firing as I already have to much fuel. This is an older 1:1 simultaneous four barrel so the left front right rear, right front left rear injector firing is fine. My problem is lower vacuum than stock 12 at idle instead of 19 so I need to adjust chip. Big cams are new to me...
 
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