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327 SBC TBI or 4 barrel carb?

Discussion in 'The Hokey Ass Message Board' started by motorhead337, Feb 20, 2011.

  1. motorhead337
    Joined: Mar 12, 2010
    Posts: 30


    I have a 1980 camaro with a 1968 327 with a 2 barrel out of a 68 camaro factory 210hp. I would like EFI so I can get better MPG, but would it give me any mope HP or take some away? I could put a 4 barrel carb on it but finding a holley or rochester for a decent price seems impossible, where as i have a truck from a junk yard with TBI that I could take the EFI parts off of. also do I get any less mpg with a 4 barrel compared to a 2 barrel?

    thanks for the help
  2. bbtom30
    Joined: Jan 10, 2007
    Posts: 155

    from so. cal

    The truck tbi is not the best f.i.,but it's still more efficient than a carb.Should get better mileage and at least as much h.p..A q-jet driven with economy in mind will get better mileage than a 2bbl.BBTOM
  3. briggs&strattonChev
    Joined: Feb 20, 2003
    Posts: 2,233


    I've gotten crappy milage with every TBI (thru 1995) pickup ive had/driven.
  4. flynbrian48
    Joined: Mar 10, 2008
    Posts: 7,172


    Far be it from me to point out that this is WAY off topic, but before this gets closed...

    Forget the TBI, unless somebody GIVES you the entire system, with EVERY sensor, the complete wiring harness and ECU, fuggedaboudit. They're OK, but to retrofit a carb'd engine is a big job. Get an Edlebrock 650 and manifold and be happy.


  5. motorhead337
    Joined: Mar 12, 2010
    Posts: 30


    well a 650 is to big.. i need a 500.. and the truck has all the parts in it and the manifold will fit on pretty easy. just wanted to know if tbi would hurt my hp at all?
  6. squirrel
    Joined: Sep 23, 2004
    Posts: 49,494


    probably not. I'd run a quadrajet, but I'm weird like that.
  7. Dzus
    Joined: Apr 3, 2006
    Posts: 321


    That rochester 2 bbl is pretty hard to beat for mpg as far as a carb goes, and I've played plenty with 327's. 4GC's, Qjets, AFB's, AVS's, Thermoquads, and more Holley's than I can remember.

    The one place that that TBI would shine is in winter driving. You would take less of an mpg hit using the TBI compared to a carb.
  8. oldcarfart
    Joined: Apr 12, 2005
    Posts: 1,437


    If worried about mpg run a quadrajet with disconnected secondaries.
  9. onedge
    Joined: May 25, 2006
    Posts: 1,000


    ^^^^that is very funny!!!!
  10. To start with a 650 CFM edelbrock is not too big for your stokc 327. I personally would opt for a 600 cfm vac secondary holley and they are pretty cheap even new but either will work fine on your chebby.

    You won't get any better MPG with your TBI and probably worse as well as loose some performance. There was a reason that GM went to tpi.

    I hate to be the one to point this out to you but you and the rest of the people in the same boat as you need to hear this. if you cannot afford a carb you cannot afford to be in this hobby. That is the same of you own a camero or a model t.

    None of you want to compare poor with me so don't even go there.
  11. derpr
    Joined: Mar 11, 2007
    Posts: 257


    If you can't afford a carb. you really can't afford a tbi swap. with all the sensors you would have to change, fuel line, fuel pump. 600 holley seams to be alot cheaper, and you could get used intakes all day for a 327.
  12. Just put the Quadrapuke on and run it.Pete.
  13. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,457


    I would run the 500cfm Edelbrock. You can make a larger carburetor work, but why? Running larger carburetors on smaller engines leave you with overhead you will never use, and leave you using just a fraction of that carburetor's metering ability, less accurately.

    I do all of my tuning using real-time electronic data gathering and logging, including an O2 sensor an vacuum gauge. Only one car that has come into my shop for tuning in the last 10 years had an appropriately sized carburetor on it. They were all to big, and some by a huge amount. All left with better performance, and much better mileage.

    Dumping fuel out the tail pipe ≠ performance, dumping fuel out the tailpipe = waste.

    If the Edelbrock is out of reach financially, grab a Q-Jet and run it. They work really well, and you can get they really cheap.
    Last edited: Feb 21, 2011
  14. carbking
    Joined: Dec 20, 2008
    Posts: 3,113


    If you are making the conversion for fuel economy only, you might want to do the math:

    P = C / [(M / N) - (M / E)] * F


    P = payback period in years
    C = conversion costs
    M = miles driven annually
    N = current average MPG
    E = expected average MPG
    F = cost of fuel in dollars per gallon

    My guess would be a 1968 two barrel engine in a 1980 Camaro might average overall 13 mpg and if you are really lucky, the same engine with no modifications other than the efi might average 15 mpg overall. The overall average would be for both city and highway driving. Only you can answer the ratio of city to highway.

    Often the payback will exceed the average life of the vehicle.

  15. thirtytwo
    Joined: Dec 19, 2003
    Posts: 2,641


    i had a 350 in a 1990 2wd truck with a got 22 mpg....and pulled my trailer awesome....i have never got anything close to 20 mpg with a carb..

    i am going to put a vortec roller motor with a tbi in a 67 pickup in my daily driver for gas milage and pulling power...gas is only going to get more expensive ....i can do without a truck that gets 10mpg... i like the idea of tbi because it is simple ...i thought of going with a lt-1 or an LS motor but crank triggers and coil packs ect. ect....scare me a little , if something goes wrong with the tbi and i cant figure it out i can always put a carb back on it

    there is a place called howells in michigan, they make custom chips and wiring harnesses for tbi... they can probably give you better info than the carb guys on here
  16. I actually know a little bit about both the TBI and carbs. Not much but a little. I'm old but not stupid.

    I regularly got 22 out of the Pusher with a single holley 600 loaded or unloaded. A carb is easier to tweak unless you are accustomed to fuel mapps etc.

    The TBI was never efficient they didn't emulsify well for starters and drooled a ton once they started to get some miles on them. They were a trade off if you are after efficiency you really need to lean towards a TPI or an SPI.
  17. grm61
    Joined: Oct 19, 2009
    Posts: 179

    from Washington

    I wouldn't go out of my way to put TBI on anything unless it was on a Jeep or something that needed to be able to run upside down.

    I have a OT 95 yukon 350 TBI 11.5 to 12 MPG gutless pig.

    I had a OT 91 chev truck same engine same MPG.

    Q jets work well if you stay out of the fun side of the carb.

    No matter what you do its not gonna be a gas miser.

    If mileage is critical, you might consider a 4 cyl commuter and save the OT Camaro for fun

    Joined: Jun 15, 2006
    Posts: 3,385


    Run the TBI "IF" you have all the harness, sensors out of a running vehicle.
    It will run great !!!
    I have run a TBI (hidden) in my gmc model A for a few years. Paint the fuel lines flat black, and the TBI eastwood gold , install a air cleaner and tell everyone its a quadrajet !!!
    Easier to start , electronic spark control ( including knock retard) will make as much hp as the carb would and parts are everywhere.
    PM if ya need any help...

  19. motorhead337
    Joined: Mar 12, 2010
    Posts: 30


    well its settled i just bought 2 Holley 600 series for $65 and a edelbrock RPM Airgap manifold for $100
  20. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,457


    My 305 gets just over 28mpg on the freeway, with a carburetor. Tuning is everything.
  21. tunram2quad
    Joined: Mar 16, 2007
    Posts: 168


    what he said..don't over carb it
  22. motorhead337
    Joined: Mar 12, 2010
    Posts: 30


    well i got a 600, I always thought those wideband O2 sensors you can get are cool, should i buy one to help tune my carb and make sure the jets arent to big? I dont really have much experience in tuning carbs..
  23. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,457


    As long as it is a vacuum secondary 600, you should be able to tune it just fine.

    Get yourself a Holley Carb Manual, from Haynes:

    Your local parts store may have it.

    And maybe this one too:

    These will go a long way to clarifying what stops most people in their tracks. Carb tuning is not rocket science, or a black art. You CAN do this!

    Wide-band O2 sensors are pretty good. Every car I tune has a bung for one hidden on it somewhere.

    This is the company that makes the equipment that I use (and the actual product):

    Best tune to date: One full second in the 1/4 mile, and a 50% increase in freeway fuel mileage, all with a 20% smaller carb.

    There is no reason your ride can't be powerful and as efficient as it can be.
  24. motorhead337
    Joined: Mar 12, 2010
    Posts: 30


    thanks, i'm only 15 but i'm glad i can get help from people like you who have a lot more knowledge and experience with this stuff. i also have a 1950 lincoln, the only thing that saves me on it is the fact i have all the parts to it.
  25. ill put my 2c in you can run the 85-86 tbi... it gets the crank trigger off the distributor, uses an O2 sensor, a map sensor in the throttle body, and a coolant sensor, most of the tech mumbo jumbo is in the throttle body. with minimal stuff bolted to the engine.. but its really not worth it its just a little bump in mpg, but not enough to save on fuel enough compared to what your going to spend putting it on. a Q jet if ya can have enough discipline to stay out of the secondaries, and a edlebrock if you cant they both have metering rods for a bit more fuel control...
  26. 1966 348 chevy
    Joined: Dec 18, 2010
    Posts: 4

    1966 348 chevy
    from mounds ok

    this is tha 283 that was built back to factory specs except we put 267 heads and a early '60s ss327 intake on it and an adapter plate to go from a four barrel to tbi, not sure of tha milage yet but i'm sure it won't be to bad since it's just 283 and i'm usin a 3 speed with O/D, one of these day i'm gonna put 2 tbi's on a old wiand or offy crossram intake, paint em with some eastwood carb paint and make look like dz 302
  27. 53sled
    Joined: Jul 5, 2005
    Posts: 5,818

    from KCMO

    you can tune it with a vacuum gauge and by reading the plugs. i'm not very good at it, admittedly, but there are those who can do it.
  28. jackw405
    Joined: Oct 6, 2010
    Posts: 9


    I'd like to keep ths going by expanding the subject slightly, I hope nobody minds. My 327 is in a 62 impala. The powerglide is roasted. It is my intention to replace it with a moderately builtup 200R, better off line and better highway mileage (I hope). In addition to that, I'm looking at hotter coil or HEI with quality plugs and wires. I thought maybe Holley at one time had a carb that was marketed with small primaries aimed at better mileage during normal driving but big secondaries for the fun driving. Am I wrong about that or for that matter anything else i have here? I would also appreciate anything on intakes that would work in the mileage and performance improvement plan. By the way it does pain me to replace these factory standard parts, they will be treated well while in storage.
  29. AHotRod
    Joined: Jul 27, 2001
    Posts: 11,416


    I'd use a Q-jet on it Jack.
    If you want a Holley, look at the old R-6210 spreadbores.
  30. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,457


    X2. Those who bad-mouth Q-Jets have little to no idea what the are talking about. They are excellent carburetors. They, like any other, do need to be kept in a good state of repair and cleanliness.

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