"Carb" swap question

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98k15

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When swapping a vortec to a carb is there any wiring that needs to be done for the fuel pump to stay on while running?
 

D_EATON

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When swapping a vortec to a carb is there any wiring that needs to be done for the fuel pump to stay on while running?

Not sure on vortec, on my tbi I didn't have to change any wiring. As long as the oil pressure switch on the back of block saw pressure it would allow the fuel pump to run.
 

slowburb

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probably, why would you go that far back in time?

Time doesn't necessarily improve things. Going back in time doesn't and shouldn't always connotate negatively. A carb'd intake is way better than any pos efi intake. A carb'd intake will give more power and do it from idle to redline. A carb'd intake will INCREASE redline, at least to the 5800 rpm hardwired rev limit of the black box computer. When carbs came on sbc's, the driver could rev the engine to the potential of the parts without a computer stopping him. A good carb'd intake tops out at $300. A good efi intake starts at $1500. A carb can be tuned with a screwdriver and a vacuum gauge. A vortec needs $900 worth of software or a competent tuner and $200+. A carb mixes fuel with air in the venturis, before the intake plenum, not via little hose in the middle of the intake port.
 

df2x4

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at least to the 5800 rpm hardwired rev limit of the black box computer.

While I agree with most of the body of that post... I see people throwing this "hardwired" black box RPM limit around a lot. Simply false. The BBP tuned black box in my V6 truck commands WOT shifts at roughly 6300.

Also any EFI system is going to run more efficiently than a carb. The carb may make more power, but at the expense of fuel mileage and drivability unless you're very, very experienced in carb tuning. Even then, good luck.
 

slowburb

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While I agree with most of the body of that post... I see people throwing this "hardwired" black box RPM limit around a lot. Simply false. The BBP tuned black box in my V6 truck commands WOT shifts at roughly 6300.

Also any EFI system is going to run more efficiently than a carb. The carb may make more power, but at the expense of fuel mileage and drivability unless you're very, very experienced in carb tuning. Even then, good luck.


Even still, computer modifications required to allow parts to work to their potential? No thanks. I'd rather go that far back in time and adjust driveability and mpg with jetting and venturi size and timing with hand tools and plug reading. Not many hotrodders are all that concerned about a half an mpg anyways.

The vortec platform just isn't conducive to shadetree tinkerers. This is not to mention the costly and almost countless sensor failures or malfunctions that can trash idle quality, driveability, mpg's, etc.
 

df2x4

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The vortec platform just isn't conducive to shadetree tinkerers.

For the older guys, sure. Now days it's becoming a lot more common for shadetrees to have Tech 2s and similar scanners laying around though. While I agree that a carb setup is usually easier to work on for the average DIYer, the Vortec trucks really aren't rocket science.

IMO it's just one of those "do what you want" things. Each setup has it's advantages and disadvantages.
 

SAATR

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I, for one, love EFI. It's definitely more complex and expensive to modify for performance, but having the ability to monitor things like AF ratio, timing advance, manifold pressure, and knock at any point in the power curve, under any conditions, at any time gives it a huge advantage over a carbureted setup with regards to tuning. Carbs can certainly make just as much power for less money, but not having to scatter the carb umpteen times to change jetting, power valves, accelerator pump cams, secondary springs, etc or pop the distributor apart to change advance weights and springs (especially on a smoking hot engine) is well worth the money.

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TylerZ281500

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900 for software hellll noooo. intake sure, the carb itself no. out of all the people who carb swap something 10% of thes gmt400 owners know how to tune a carb if you can great but we arent talking personal opinion here were are talking factual information.
 

MarkZ28

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Actrually, a carb can make more power for a lot cheaper, but, as stated, its not as easy to tune as far as time goes. I much prefer carb and am going to swap to carb and aftermarket aluminum heads, cam, etc. also. I know EFI is better for mileage, smog crap, and instant on the fly tuning.
As far as tuning a carb, there are kits that allow you to change jet sizes with a screwdriver without removing the metering blocks. That makes it a lot easier and no mess. Thats on a Holley, the carb I prefer. I have always had good luck with Holleys keeping their tune and dont go up high mountains daily so no wory about elevation changes and air/fuel mistures being off that much.
 
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