Carb swap on a 90 GMC Sierra
11-05-2005, 02:48 PM
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Carb swap on a 90 GMC Sierra
I own a 90 GMC Sierra with a 5.7l tbi engine in it. I hate the tbi and i dont want to waste my money on this junk when i go to rebuild the engine. I am currently considering running a carb'ed setup. I was wondering what all i need to do to completely do this swap. I realize that i will need a carb intake, carb, hei distributor, and a lockup controller for my 700r4 tranny. What else will i need to do? I noticed that the coolant temp sensor is hooked in with the efi harness, someone correct me if im wrong on that one. Also would I am looking at getting a holley 600, i can either get the 600 or the street avengar 570 for my application. Which is better to run, a mechanical secondary carb or a vacuum secondary carb? Any help on this topic would be greatly appreciated.
11-06-2005, 06:37 PM
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your going to need a fuel pressure regulator, your fuel pump is going to put out way more fuel pressure than needed for a carburetor and it probably wont run with out one. i'd go for a mechanical secondary carb if your really going to be in for performance.
11-06-2005, 07:56 PM
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Im planning on running a a mechanical fuel pump for the time being. I found out how i can get power to the distributor and a few other things. I am planning on leaving the stock computer in the truck so i can still have the coolant sensor hooked up to it and a few other things. If i leave the stock computer in the truck but unhook all of the connections for the efi, will it still lock up my transmission when its in overdrive or will i have to buy the lockup kit?
11-10-2005, 10:02 PM
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i have seen some of the later model blocks have the mounting point for the mech. fuel pump, but in the casting of the block it is blocked off. If this is how yours is, you may want to run the stock intank pump. For simplicity on the trans lock up, it would probably be easier to use am aftermarket lock up harness.
11-11-2005, 07:17 AM
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Originally Posted by Formulized94
i have seen some of the later model blocks have the mounting point for the mech. fuel pump, but in the casting of the block it is blocked off. If this is how yours is, you may want to run the stock intank pump. For simplicity on the trans lock up, it would probably be easier to use am aftermarket lock up harness.
I took a look the other day at the block to see if i could run a mechanical fuel pump and it does have the plate over it but only has five bolts holding that blockoff plate on. I was also considering running the b&m lockup kit after i got to thinking about it. If i was to do this swap and i unplugged the fuel injection harness from the computer, would my guages still work off the computer?
11-12-2005, 09:43 PM
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Why not use a 454 Throttle body? You can buy and adapter, and the 454 TB is 700cfm I think. You can run a fairly larger cam, some long tube headers, all you would need is a custom somputer chip...should cost $150-$200 for the chip. I think you're asking for trouble going to a carb setup. You could always swap a TPI setup...a speed density(90-92) setup is similar to the throttle body(batch fire injectors). Just a couple of ideas.
Dave
Dave
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11-13-2005, 07:45 AM
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if you are planning on going back with a carb i would use a demon. http://www.barrygrant.com/. a speed demon or a mighty demon should work very good for you.
11-13-2005, 09:18 AM
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You will also need an adjustable regulator, prefferably with a return. You need the TV cable corrector for the carb to keep the line pressure right in the carb and a cable bracket that positions it coreectly. For a lock up controller you can do like I did and have it just lock up in 4th gear only, and it will do it automatically. Personally if you are only going to go 600 cfm then dont bother. You can make good power with a TBI, especially with the aftermarket units available, and a chip isnt always neccesary. I ran my truck withteh stock chip and a 220/230 .510" cam. I just used an adjustable map sensor, fuel regualtor and a few other high performance TBI stuff. Check turbo city, they have some good TBI performance parts. The bowl they have for under the air cleaner helps a lot, the injector spacer helps some, the larger units flow 700 cfm which can support a lot of power.
I did the swap, but I went with a 750 carb. For switching a then just going to a 600 it makes no sn=ense.
I did the swap, but I went with a 750 carb. For switching a then just going to a 600 it makes no sn=ense.
11-13-2005, 11:28 AM
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Originally Posted by oneslammedgmc
I took a look the other day at the block to see if i could run a mechanical fuel pump and it does have the plate over it but only has five bolts holding that blockoff plate on. I was also considering running the b&m lockup kit after i got to thinking about it. If i was to do this swap and i unplugged the fuel injection harness from the computer, would my guages still work off the computer?
I would think that your guages should still work, like the temp, oil pressure, and such.