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Will A Few Of These Modifications Get A Few MPG Gain Out Of A 1983 C20 Suburban 454 Carb TH400 Duall

Discussion in 'Intakes and Exhausts' started by Tillard, May 17, 2018 at 4:51 PM.

  1. Tillard

    Tillard New Member

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    May 15, 2018
    New Orleans, LA
    IMG_20180410_132211.jpg Got a 1983 Suburban C20 Dually Converted with a 454 Carbureted and Turbo400 transmission.

    The 454 already has installed longtube headers and need a valve lifter adjustment due to "tapping" noise.

    Here's a list which I ask that may it help the 454 gain a few mpg if not alot; Vortec Heads, high power spark plugs, high power coil pack and ignition coils, plastic air intake manifold, and maybe switch from carbutcarb to fuel injection.

    I'm not looking for performance and racing. just mainly some if not alot of efficiency. somewhat close to a 305 or 350.

    Also I don't drive fast like a maniac, I take my time and drive the speed limit with smooth takeoff/accelerations
     
    Last edited by a moderator: May 18, 2018 at 8:15 AM
  2. Jaryd

    Jaryd Oh the sound a 6.5 makes

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    Dang dude, that’s a good looking burb.

    The heads and fuel injection would probably get you the most mpg gains.

    What gear ratio do you have.
     
    Tillard likes this.
  3. Tillard

    Tillard New Member

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    not really sure but when you step on the throttle lightly it gets into third(last) gear before 25 or 30 mph
     
  4. Tillard

    Tillard New Member

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    It gets me where I got to go. Some of the paint is falling off which I may have it repainted green military color with black rims
     
  5. ak diesel driver

    ak diesel driver 6.5 driver

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    I was thinking more along the lines of a 4l80e with a standalone controller
     
    dangerousdave, Jaryd and Tillard like this.
  6. Will L.

    Will L. Well-Known Member

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    Jan 25, 2013
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    I agree 100% with above. Overdrive is what will help the most. Lower rpm at cruise speed and easier acceleration.

    After that the fuel injection will help a bit. But it isn’t fuel injection alone that give newer rigs better mpg, it is the elaborate computer control system with all the sensors to tell it when to add or cut back fuel and when to advance or retard timing.

    Also you could look into a turbo. In my experience turbos add 10% mpg to diesels and 8% to gassers.
     
    dangerousdave likes this.
  7. WarWagon

    WarWagon Well it hits on 7 of 8...

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    AZ
    Best MPG improvement for a 454 is put it on a trailer:

    75.jpg
     
  8. THEFERMANATOR

    THEFERMANATOR FRANKENBURBAN Staff Member Lead Moderator

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    May 9, 2008
    ZEPHYRHILLS FL
    You can spend a couple grand, and maybe eek out double digit mpg's. A 4l80e swap would probably help you more than anything dollar wise. Otherwise your next best option would be to yank the 454 out, and swap a lq4 6.0l/4l80e back in it's place. The 454 is never going to give you great mpg's and all the stuff you're talking about is going to cost you more money than a modern engine swap would cost you. I know I just posted up a few weeks ago about a 8.1l/4l85e combo for $1700. That would give you way more power and mpg's than the 454 could do even with all your listed mods, and probably cost you less money.
     
  9. Tillard

    Tillard New Member

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    Not bad for a 6.0 and 4L80e. im just afraid of the wiring and all to put all that in the vehicle
     
  10. Tillard

    Tillard New Member

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    New Orleans, LA
    why not a 5.3 with a 4L80e
     
  11. ak diesel driver

    ak diesel driver 6.5 driver

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  12. Tillard

    Tillard New Member

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    New Orleans, LA
    Huh?
     
  13. ak diesel driver

    ak diesel driver 6.5 driver

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    5.3 is a great engine but you'll lose alot of bottom end compared to the 454
     
    Tillard likes this.
  14. Will L.

    Will L. Well-Known Member

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    Going to the 8.1 is best power and mpg compared to 454 as mentioned. A smaller option if you don’t need that much torque would be the 6.0 with 4l80e.

    I had a 99 2500 4wd suburban, stock other than tires. 6.0 4l80e. It got 15 mpg empty and doing speed limit. But my wife and I are frequently at risk of unhappy hiway patrol. So 13.5 was most common. Loaded and towing a camp trailer, or driving like a total a-hole (yes sometimes I would get it to the 120 mph range) it still brought 11 mpg. I only changed the engine oil in it every 30,000 miles and tranny oil only happened by mistake before we sold it with over 200,000 miles on it. Rode hard and put away wet doesn’t even begin to describe it. LOVED that engine.

    Really makes me think about a gasser hummer getting a hot rod built 6.0 and selling my 6.5, but then realize the 6.5 keeping me slower is probably the smarter choice.

    Also, the 454 and th400 can resale for some descent cash if you take video of it running and hold firm to a fair price. More and more guys out there wanting old school big blocks for the authentic car builds. Dont just advertise it Craigslist, get the word out to the hotrod groups in your area.
     
    WarWagon, Jaryd and Tillard like this.
  15. Tillard

    Tillard New Member

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    And take the cash from the sell of the 454 and transmission and put it towards a 8.1 or 6.0 with a 4L80e
     
  16. Tillard

    Tillard New Member

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    New Orleans, LA
    I might do like u said and get the 8.1 because you dont know when you need the power. plus I'm not hard on the throttle like a maniac, iIgo the speed limit which is mostly 35 mph off the interstate here in New Orleans.

    The one thing that intimidate me is when or if I put in in a 8.1 or 6.0 engine inside the vehicle , along with the transmission is the wiring duties that comes along with it which seems complicated along with the computer program.
     
  17. Will L.

    Will L. Well-Known Member

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    The ls engine is now the most commonly retro fitted engine out there. There is a company in North Las Vegas doing them into Jeeps that turn out amazing.

    Spend the $ and get a proven kit. You will need to put some miles on it to have the fuel savings pay for itself. But once you drive it with the new engine/trans- you will want to drive it everywhere.

    I HATE electronics in vehicles. That’s why I walked away from wrenching. I love carburetors and mechanical injector diesel pumps. I also like free falling from airplanes. But I am old enough to know there are certain things I just shouldn’t do anymore. When a chute pops open that yank on my back isn’t good anymore. Neither is the money that has to pour through a carburetor, or its wanna be cousin the throttle bodied injection system.
    Injectors need to screw into heads, not my wallet. I still think diesel injection pumps should be mechanical though.

    Don’t feel alone in the: I hate electrons category. Hilariously, an electrician for my paycheck.

    But just add gas and drive is so easy and affordable long term with the newer engines, that many of us diesel nuts have to appreciate gas engines once again. Slowly some are switching over. Unless you tow heavy frequently, it just makes more sense. And more cents.
     
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  18. Tillard

    Tillard New Member

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    I might get a donor vehicle to come to think of it, that is wrecked like a Chevy van that may have a 8.1 amd 480l transmission . that may make it somewhat simpler to transfer and be less expensive than getting the whole engine and transmission itself. unless im lucky to find the engine and transmission at a good price
     
    Will L. likes this.
  19. Tillard

    Tillard New Member

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    Nice Humvee too. I rather those than the H2 amd H3 Hummers that aren't Hummers
     
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  20. Will L.

    Will L. Well-Known Member

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    Yeah, but if you convert it yourself using all factory stuff instead of the stand alone kits, way too much hassle. All the body control stuff, airbag crap, the complete difference of dash gauges- it is cheaper and easier to go kit.

    Thanks on the hummer thing. I don’t beat up on h2&3 much. They are just a different body style tahoe imo for the h2, but have better approach and departure angles. H3 is like an offroad improved Colorado/ blazer. Not a fan of the 5 cylinder though.

    My Hummer is like a lifted single wheel 1 ton with really short pickup bed. Enough room for spare parts to break off road and carry lots of food and ammo. Roof rack is for campin gear or dead zombies.

    I got it stuck once, (high centered) but had to try hard to do it. Took a 5.3 chevy c2500 and k2500 duramax to drag me free. I swear one day I should get a dirt anchor for my winch. I was too sore that day to go anchor the winch. Haven’t needed it since then. Knock on wood-
     
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