Author Topic: EFI or Carburetor - Which way to go?  (Read 1820 times)

Offline Twosquarebodys

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EFI or Carburetor - Which way to go?
« 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. 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? 
87 R10 358 CID 700R4 <> 86 C-30 1 TON 454 W/NV-4500 <> 05 SILV 2500HD 6.6 DURAMAX/ALLISON

Offline zieg85

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Re: EFI or Carburetor - Which way to go?
« Reply #1 on: May 27, 2022, 09:55:18 PM »
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
Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline VileZambonie

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Re: EFI or Carburetor - Which way to go?
« Reply #2 on: May 28, 2022, 06:34:15 AM »
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.
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Online bd

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Re: EFI or Carburetor - Which way to go?
« Reply #3 on: May 28, 2022, 10:09:03 AM »
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.

Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline zieg85

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Re: EFI or Carburetor - Which way to go?
« Reply #4 on: May 28, 2022, 03:46:56 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. 

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
Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline Stewart G Griffin

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Re: EFI or Carburetor - Which way to go?
« Reply #5 on: June 12, 2022, 03:03:13 PM »
What a problem to have.......

i think it boils down to which do you like?

i like having FI on my daily----i like just being able to turn the key and it starts (although, the carb is generally like that too except you have to press the accelerator down before turning the key).

But the carb on my square works good too.

A lot of the newer SBC blocks do not have a provision for mechanical pump, so you have to run an electric pump  anyways.  The LS's don't either.  So the electric vs. mechanical pump argument is less of an issue to me these days.

i think carb is still cheaper.  And carb MIGHT still be faster/easier/more straightforward to install and get the engine running?  i said, MIGHT.  EFI is getting easier and easier.

To me, it boils down to:  What do you like.

Offline peewee0413

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Re: EFI or Carburetor - Which way to go?
« Reply #6 on: July 05, 2022, 10:06:21 PM »
I built a 350 in a 93 k1500 and during the paper phase of the build I almost went carb over EFI due to the fear of tuning. Ultimately made the decision to go EFI, and it was a good decision. I don't bother with anything, Spark and fueling all at the touch of a button. I have a travel/daily tune and a hot tune. Take 15 seconds to switch. Same goes with my tranny tuner running a Performabuilt Transmission. Flip of a toggle switch changes a tune (shift points and pressures change.) As stated, it's still a personal choice.

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