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which FI- TPI or TBI

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Nonesuch, Oct 20, 2001.

  1. Nonesuch

    Nonesuch 1/2 ton status

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    I have been using the K5 for a daily driver recently and I have got to increase the fuel economy. 90 miles burned up about 9.5 gallons of gas. anyhow, i was wondering the pros and cons of TBI/TPI and which i would benifit from the most? I drive pretty good most of the time and only get on it when i have to or need to show off all my head snapping power hehehe yeah right!
     
  2. WheelinK5

    WheelinK5 Registered Member

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    670 CFM Pro-Jection® / Holley
    Two Barrel Digital
    GM, Chrysler, Ford & AMC V-8s

    Part #: 502-20S Shiny finish

    $650.00-750.00 This is what I am getting.

    <a target="_blank" href=http://www.holley.com/HiOctn/ProdLine/Products/FMS/FMSFI/502-20S.html>http://www.holley.com/HiOctn/ProdLine/Products/FMS/FMSFI/502-20S.html</a>


    1985 K5
    Built 330HP crate 350, SM465, NP208, 10 bolts, Ranchos and 31X10.5 on Rallys!
     
  3. zakk

    zakk 1/2 ton status

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    asking TBI or TPI is one of those eternal questions. there is no one opinion, IMHO. When i am able to afford parts again, i think i will also be going with the afore metioned holley TBI system. I like the idea that it all comes in a box and there is no chance of a mix-up with the computer stuff. Wrecking yard axle's are one thing, electronics is completely different.
    plus the holley TBI is 100's less than anything else on the market unless you want a 2k DFI Edlebrock system [​IMG]

    -Zakk
    '77 K5 SB 400 TH350 NP203 p/t 6" Lift D60 14BFF 4.10's 36"Wrangler II's

    [​IMG] CK5's MOAB 2002 OR BUST!! [​IMG]
     
  4. CaptCrunch

    CaptCrunch 1/2 ton status

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    TBI won't improve you milage much... well at least not enough to verify the expense IMO if that is all you really want iot for. It is great for angles, cold weather starting and drivablity though. A TPI swap would be where it's at! Milage... power, but also takes some decent mechicanical knowledge and some $$$.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <a target="_blank" href=http://coloradok5.com/gallery/captcrunch>http://coloradok5.com/gallery/captcrunch</a>
     
  5. Nonesuch

    Nonesuch 1/2 ton status

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    well not only milage but cold weather starting, angles, the whole sha-bang. If TPI will net me better MPG then thats the way i will go. my new job requires about 600 miles a week so i think it will pay for itself pretty quick.
     
  6. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    You can get lucky and score a TBI unit for cheap... I got mine for $100 bucks. I have to buy lines and a fuel pump (someday it'll go in when I can afford the other toys I want put in with it!).

    Also I'm just wondering about any stuff you have done to your rig? Like maybe a K&amp;N filter...changing the plugs and wires, maybe a new dist cap/rotor... fuel filter? Heck I have heard people changing those things and it makes a big difference. I know when I changed my O2 sensor it ran better instantly. Check out stuff like that too. Be surprised what it could do for ya! Sometimes it's the little things that screw ya up the worst. [​IMG]

    &lt;&gt;&lt;<a target="_blank" href=http://www.chevycagal.homestead.com/steph.html>Steph's Webpage</a>&gt;&lt;&gt;
    Suck Fumes Ford Boy
    I keep trying to lose weight, but it always finds me!
     
  7. WheelinK5

    WheelinK5 Registered Member

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    OK here is the ultimate in fuel injection!

    <a target="_blank" href=http://www.edelbrock.com/automotive/mpfi_proflo.html>http://www.edelbrock.com/automotive/mpfi_proflo.html</a>

    BIG improvement in fuel mileage AND major performance improvement. The problem? around $1600-1800.00 if I remember correctly.

    Mark

    1985 K5
    Built 330HP crate 350, SM465, NP208, 10 bolts, Ranchos and 31X10.5 on Rallys!
     
  8. hammer

    hammer 1/2 ton status

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    I have been looking at a TPI out of 85 camaro and they say it is the best way to go for gas milage and power
     
  9. WheelinK5

    WheelinK5 Registered Member

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    The TPI was designed for the 305. It is a great system for lowend power. If you want any power above 4500 rpm don't go TPI.

    Mark

    1985 K5
    Built 330HP crate 350, SM465, NP208, 10 bolts, Ranchos and 31X10.5 on Rallys!
     
  10. Nonesuch

    Nonesuch 1/2 ton status

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    running K&amp;N air filter (just cleaned it today), new plugs, wires, and coil last weekend, tuned the Q-Jet a little cause she was running RUFF(needs a rebuild), put a new cap and rotor on with the 305 to 350 swap, fuel fiter was checked and still clean and last but not least no O2 sensor cause all emission parts were scraped by previous owner.

    Thats a hell-uva deal on your TBI chevycal. did that include the ecm and harness?
     
  11. 84_Chevy_K10

    84_Chevy_K10 Banned

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    TPI came on 350 powered IROC-Zs too.

    I wouldn't even waste the time to put TBI on my truck. Mine will have a carb until I can afford port injection.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  12. Thunder

    Thunder 3/4 ton status

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    Hmm TBI or TPI?
    Well TPI is good but it is very expensive and you wont get any beter gas milage than with a TBI. But you should get more power. Parts are also expensive and hard to find.

    The Holley system works pretty good and should improve your milage over your carb. It is a direct bolt on without any mods.And the price is right. Once you get them adjusted they run pretty good. A buddy has one on his Sub it seems to work ok but he has had some injector problems.He gets around 15 mpg. I know another guy who put one on his boat and hated it. He took it off and went with a GM TBI system. Parts for the Holley are also not available everwhere and usually have to be orderd.

    Which brings me to the best TBI made. The GM / Rochester system. I think this is the best fuel delivery system made for a truck. It is simple, reliable, easy to work on and just works good.
    I get very good gas milage with my TBI. I have modified it to improve air flow and tweaked the sensors to get even more power and economy out of it. I get 20 mpg average and can do 25 mpg on the highway if i keep it under 65. I am also developing some serious power for a stock 350. There are a lot of aftermarket parts for TBIs to make them run very well and develop real good ammounts of power with out sacrificing gas mileage.
    It would be a vast improvement over a carb.
    Check out these guys. Link:http://coloradok5.com/gallery/Thunders-Blaze
    <font color=blue>NEVADA: Where the pavement ends, and the West begins.</font color=blue>
     
  13. Nonesuch

    Nonesuch 1/2 ton status

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    thanks thunder! that link is very appreciated!
    Justin
     
  14. WheelinK5

    WheelinK5 Registered Member

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    20-25 MPG? WOW!

    1985 K5
    Built 330HP crate 350, SM465, NP208, 10 bolts, Ranchos and 31X10.5 on Rallys!
     
  15. HarryH3

    HarryH3 1 ton status Author

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    Not to bust your balls, but I think that perhaps your odometer is messed up. [​IMG] I've had several K5's and none of them could ever make it to even the 15 MPG mark, no matter how I drove. 25 mpg seems like a pretty big stretch for five thousand-plus pounds of non-aerodynamic brick rolling down the road. Even my wimpy little 4.3 liter powered S-10 has a hard time making it up to 20 MPG on road trips. My TPI 383 powered '75 gets a tad over 13 MPG on the highway. The wife's '94 stock 350 powered Sub can squeak out 14 MPG. 25 just seems like wishful thinking. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  16. marv_springer

    marv_springer 1/2 ton status

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    25 mpg?!

    You got Pamela Anderson riding "shotgun" w/ you too??!

    If you're really getting that good of mileage... more power to ya,.... but I'd have to see it to believe it!

    Marv
     
  17. Thunder

    Thunder 3/4 ton status

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    I really dont care If anyone believes me or not. I'm not trying to sell anything..... I am just trying to help someone out Not all vehicles are the same and many peolpe dont like to tune and adjust on their vehicles like I do.
    The odometer is right on.And It is not wishful thinking. As I said in my posts I have modified the TBI and MAP sensors, ign and a lot more.. 20 mpg is an easily attainable goal . I just did a milage test on my truck it went 1100 miles on 54 gallons of 89 octaine gas do the math. My truck is also in excellent mechanical condition. And the 700r4 really helps.
    There are many here on this board that get 17 miles to the gallon and up with a TBI. Before I started bolting on stuff I got 17 miles per gallon average
    I think I have taken it about as far as I can. My Blazer is my daily driver. it is also the vehicle we use to travel in a lot The reason I bought it was because it was a TBI and so easily modified, and can be tuned to give both power and gas milage. I like TBI a lot better than the TPI on my other vehicle that I pretty much cant do anything with but put a chip in the comp.
    I could not afford to drive it every day if I was getting 15 mpg.
    I have to say that i dont think I could get as much power out of a TBI as you get out of TPI but I built my K5 to get good gas milage not win races. Hmmmm..... come to think of it many races are won because of good gas milage[​IMG].


    <a target="_blank" href=http://coloradok5.com/gallery/Thunders-Blaze>http://coloradok5.com/gallery/Thunders-Blaze</a>
    <font color=blue>NEVADA: Where the pavement ends, and the West begins.</font color=blue>
     
  18. RESTORE89

    RESTORE89 1/2 ton status

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    hey harry,[​IMG]
    my 89 with a worn out 350 gets 17mpg on the highway at 77 with the cruise set and
    on flat land. i could prob get close 2 20 if i would drive a little slower
    also a buddy has a 93 2 wheel drive burb and he gets 19 on the highway at 75, but
    the area around here is real flat and at sea level so maybe that makes a difference
    question is hoow much time and money does it take to get the added mileage[​IMG]

    It needs a bigger motor.
    what's in it now?
    doen't matter it NEEDS A BIGGER MOTOR
    89 350tbi/700r4h/np208/4.11's
     
  19. Nonesuch

    Nonesuch 1/2 ton status

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    and the war begins! lol j/k. this is a real hard choice for me (TPI/TBI) but i am leaning towards...hell i still dont know. I guess it will depend on what i find for the best money. I am searching for a GM engineered FI system because i have heard to many bad things about the aftermarket products available. I wish i would have thought about it before i bought an 83 model. this headhache would have never started. Im not looking for 20 MPG but if i get it great! 17 would be more that enough to pay for what ever system i choose with in a years time.
     
  20. HarryH3

    HarryH3 1 ton status Author

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    20 mpg is reaching pretty high, but your earlier post said 25 mpg. Using your trip numbers from above, let's take a look at what would happen with just a 10% odometer error. 1100 miles on 54 gallons of fuel would then become 990 miles on 54 gallons. That drops the mileage number to 18.3 mpg. [​IMG] Still great mileage for a K5, but it shows how just a little bit of odometer error can affect mileage calculations.

    If you can get 25 mpg out of a K5, then the engineering folks at GM would pay you mucho bucks to divulge your secrets. [​IMG] Check out the mileage stats for the new Tahoe (closest thing GM has to a K5 these days) at http://www.chevrolet.com/trailblazer/features.htm#fueleconomy [​IMG]



    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     

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