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ECU prices and which one do I need???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 55Willy, Mar 17, 2002.

  1. 55Willy

    55Willy 3/4 ton status

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    Hello- I am bringing the past into the present and putting TBI onto the Willy's/forums/images/icons/cool.gif
    I was able to get the throttle body and intake for dirt cheap and with the heads off the same motor, which is a 91 as compaired to the stock 78 heads that I have. The set up is off a 91 IROC 305, heres my questions.
    Do I have to use an ECU of the same car?
    Will any 305 ECU work?
    What dist. do I use?
    Anything I need to do special to get the 91 heads on the 78 block( push rods, rocker arms??)
    The deal was too good to pass up.
    TIA
    -Jeremy
     
  2. CaptCrunch

    CaptCrunch 1/2 ton status

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    You'll want an ecm that matches the TBI unit you are using... the car, truck, 305, 350 models all have chip variations. I also would not recoment using the 305 heads on your 78. Some guys do it but the compression ratio is high and I think those heads are chokers even for a 305. You can buy an intake from Edelbrock, Holley opr a few others that will bolt a TBI unit on to a standard earsly sbc heads. You also could use an adapter plate to keep your old intake and heads. I know the one that I used to run and now is in my back shead is made by holley.
     
  3. 55Willy

    55Willy 3/4 ton status

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    Whats wrong with the heads?
    why whould the intake not bolt up to my current heads?
    and whats wrong with the stock TBI Aluminum intake?
    I priced the ECU for the 91 IROC and it's $60.
     
  4. CaptCrunch

    CaptCrunch 1/2 ton status

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    First things first... the TBI heads and TPI heads have a different bolt pattern, angle, and valve cover then the 86 and earlier traditional sbc heads. Just like the vortec heads differ from both the above types. Thus the intake is different for each set of heads, but at this stage in the game, either Edelbrock, Holley, or GM Perf. Parts, has an intake that will allow you to bolt up whatever you want wether it is a carb, TBI, or TPI. Basically you stock 305 intake would bolt up to some TBI or TPI heads or aftermarkets designed for this nitch such as the TBI HP models offered by GM Perf Parts. All the heads can be found for pretty cheap on eBay... I would look for a 350 model because the 305 design IMO is a power sucker... ESPECIALLY if you want any performance over4 g's. I don't push my truck past that often, but when I do it is nice to not bog out or fall on your face trying to get through mud, over a hill, or rocks. Plus the cc size differs for the 305 heads, so if you bolt them to a 350 lower it is gonna send your compression WAY up. Too much BS to deal with IMO. Also keep in mind the injector size and flow of that 305 TBI unit. You may want to just for get it and find a 454 or holley aftermarket unit depending on the power you seek. Otherwise an upgrade in injectors may work fin too... again eBay has a lot to offer for stock stuff.

    I'm personally ditching alot of my TBI stuff in the up coming months. I'm throwing in a whole new motor and either going to a Holley TBI, 800cfm caddy 500 quadrajet, or if I can find a good deal go with a older TPI system. Everything will probably be going on vortec heads with a 3 angle and port matching. The main question will be the lower end (350..383...400) and roller or non-roller. The point being depending on what your plans are, I will most likely be ditching my stuff soon, just depends on how much denario I spend fixing my stupid drivetrain /forums/images/icons/mad.gif. So at least one setup shopuld be around soon if you don't have your beast rolling by then.
     
  5. CaptCrunch

    CaptCrunch 1/2 ton status

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    BTW... have youthought of just building a stout modified 305 motor if it is going in the willys? I know a guy running a nice 305 (it is tpi though) in his toyota pickup and it rocks! Just an idea
     
  6. Sledge

    Sledge Registered Member

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    GM used a couple of different ECMs for TBI; my info shows a part number of 1228746 being used for 89-91 F-bodies & Caprices.

    The pinouts appear to be very close to '747 ECM used in trucks, but not quite the same. On the plus-side it just looks like the F-body wiring includes some extra stuff that truck ECM doesn't. I'd say you should be able to run your F-Body setup off a TBI truck ECM w/o any real problem.
     
  7. 55Willy

    55Willy 3/4 ton status

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    I sent this in the PM as well but thought I would post it here too.

    The motor I have is a 305, it has 160K on it and smokes that was when I found it was a 305 cus i ran the numbers to check the heads to see if my other heads would work. So I talked to my friend and he gave me his heads 50K miles, intake with throttle body for next to nothing, So i was planning on bolting the heads on, intake and throttle body, getting the ECU from the junk yrad, it's $60. The wire it all up with a Painless kit, real simple and nice to work with then missing with a stock set up.
    A 350-383-400-406-396-427-454 are all out of the question..I have no money to build anything.
    As for a 305 to die out above 4 grand, I ran the burb this motor was in, it ran good, just tired, plus lugging 6300 pounds around didn't help the 305,LOL. So it will work for now til I get eveything else squared away..other projects, a job....bills bills bills...
    Thanks for the imput.
     
  8. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Just to elaborate a little more on that great explaination that CaptCrunch gave. The 305 heads runs a 58 cc chamber, where as your 350 heads are 76cc, big difference. Your 8.5:1 Compression will go past 10:1, and you'll be pinging like no tommorow. I don't think you want to burn jet fuel in it now just to keep from pinging, haha. The valves are also smaller and give alot less flow. If you thought things were bad now, then try that smaller head.

    If you really wanna be cock of the walk, then go get some vortec heads and the TBI intake with vortec bolt pattern. Make sure you go to the bank too, haha.

    Just go get an old set of 350 heads and plane them down to about 64cc-68cc, smooth out the ports, and have new guides put in (don't knurl them, if they start talking about that, find a machinist thats less lazy). Then go get and edelbrock intake and have some fun. With 64cc heads, you'll get something like 9.5:1 compression, which is perfect for a cast-iron head on 91 octane gas. A 68cc would put you around low 9:1 and you could get away with 89 octane.
     

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