73-87 Chevy _ GMC Trucks > Performance
EFI or Carburetor - Which way to go?
Twosquarebodys:
Hello square body world, just read treads on 454 and carbs. Now questioning myself on whether to do EFI swap. Just acquired 86' c30 dually long bed 454 manual trany, and removed the SM465 for a NV4500. The most weight I will ever pull with this truck is 8500lbs. My next move was EFI and lower gear ratio for fuel economy and performance. This motor has not been touched, and even has the smog pumps still on it and working. 192,000 original miles. I know some of you will be heartbroken for me molesting this truck and deep down it would be nice to restore to its original condition, but I need a driver not a garage queen. So, am I on the right track with this build?
zieg85:
Back about 10 years ago I researched the subject extensively. Long story short, I came to the conclusion that going EFI on my 85 454 4 speed would probably give me worse fuel economy based on finding worse results reported. A properly tuned Q-jet and properly functioning ignition system gets the job done. Everyone says the EFI has better drivability but everything equal I couldn't fault my Q-jet on my 85 at all. When gas was gas I routinely saw 15.5-16.0 MPG combined
VileZambonie:
Fuel economy? :P Is that even a thing these days?
I would suggest you do your gear ratio change and see how it does first.
bd:
Generally speaking, electronic fuel management systems are more responsive with better fuel control than most carburetion systems. Consequently, vehicles with electronic fuel delivery are friendlier and easier to operate across a broader range of conditions when compared to carburetion. Still, you need to maintain perspective. With respect to our generation of trucks and their crude powertrains, fuel economy and performance are not synonymous.
That said, did you mean to say EFI, or TBI, versus OEM carburetion? If you're thinking TBI, are you toying with an original equipment GM or an aftermarket system? Since your primary concerns are fuel economy with good drivability, you limit your choices and either should stick with a properly functioning Quadrajet (QJ) carburetor or narrow your focus to a factory GM TBI system from a donor truck (although the availability of viable donors is becoming more scarce as time progresses). Otherwise, most EFI and many TBI conversions are aftermarket systems that flow significantly more air than the factory TBI and QJ.
It is fair to say that properly tuned electronic fuel management systems can produce better fuel economy and definitely produce greater torque with smoother drivability. Unfortunately, that satisfying improvement in torque is perpetually tempting. You will use it routinely, especially when paired with a big block. And, fuel economy will suffer proportionately because the engine will consume more air, which correlates to more fuel. Or, at least, that is the typical scenario.
I agree with Vile. Begin with a gear ratio change.
zieg85:
--- Quote from: Twosquarebodys on May 27, 2022, 07:12:03 PM ---Hello square body world, just read treads on 454 and carbs. Now questioning myself on whether to do EFI swap. Just acquired 86' c30 dually long bed 454 manual trany, and removed the SM465 for a NV4500.
--- End quote ---
Most dually rear ends are 4.10 geared. With the NV4500 5th gear should be around 2.99 which may be all you need. I was pretty happy with the all around performance of my 3.21 but I actually loved the NV4500 in my 2001 2500HD with the 4.10 and a 6.0L, I still only got a best of 16mpg on the highway.
Remember you are moving a brick with ears (dually fenders) not the best in aero design
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