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LT4 GM crate motor

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by lehtola, Mar 29, 2001.

  1. lehtola

    lehtola 1/2 ton status

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    Anybody out there put or thinking about putting a GM LT4 (335 HP) crate motor in your blazer or jimmy? I've talked to a few folks around here and they said there would be no problem putting it in my jimmy and using the original tbi. what about you all? What have you heard?

    LT4 Part Number 12371172

    1990 GMC Jimmy 350/TH700R4/NP241/10 bolts, 4" skyjacker lift, 35x12.50R15 BFG All Terrains on 15x10 AR Baja's, Flowmasters.
     
  2. HarryH3

    HarryH3 1 ton status Author

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    At the very least you would need to reprogram the computer. Your stock TBI is programmed to provide fuel for a 200 HP engine. It takes way more fuel to make 335 HP. You'll probably need different injectors as well to keep up with the fuel demand.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  3. Emmettology 101

    Emmettology 101 3/4 ton status

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    I second what Harry said, plus you may need larger injectors.

    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; <A target="_blank" HREF=http://emmett.coloradok5.com>http://emmett.coloradok5.com</A>

    "Pimpin aint easy!"
     
  4. BMR

    BMR 1/2 ton status

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    I am about to put a GM crate motor in my 85 K5 I was looking at the LT4. I have heard only good things.
     
  5. Twiz

    Twiz 1/2 ton status

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    I don't have any info on a LT4 p/n 12371172, I might have missed it. I do have some others;
    P/N 12497317, HT383- never made production (bummer!), it WAS a 383 w/over 400ft/lbs of torqe from 2500 to 4000.
    P/N 12486041, 350HO- 330hp @5000 380 ftlbs @ 3800 $2250
    P/N 12495515, RamJet350- retro style injection manifold, ecm,wireing, 350hp@5200 400ftlbs @ 3500 $4200
    P/N 12496769, fastburn 385- alum.fastburn heads on a ZZ4, 385hp @5600 385ftlbs @ 4000 $4200
    P/N 12497323, RamJet 502- same as the S.B. 510hp @ 5500 550ftlbs @ 4500 (sit down for this one) $9000
    P/N 12371054, HT502- towing engine, 338hp @ 4500 (get this!) 512 ftlbs @ 2800 (it's a gas engine) $5000

    I know thats not what you asked, but thats what I got. The prices are ball parked, and will probably be alittle higher for non-employees. I think I might have a addiction setting in, I went to work and did some ColoradoK5 homework!!!
    Hope this was O.K. with ya-all?

    Twiztid
     
  6. BigJohnson

    BigJohnson 1/2 ton status

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    So they don't make the HT383? They sell them at www.paceparts.com. It makes 325hp @ 4500RPM and 415ft.lbs of torque @ 3500RPM. They are resonably priced at $2,679.95. I want one for my Blazer so I hope I can get one.
     
  7. Twiz

    Twiz 1/2 ton status

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    Don't know, thats what the parts guy told me. THAT IS THE ENGINE TO HAVE!, the one I priced out was P/N 12497317-HT 383 in the 2000 GMPP catalotg, Check this out (as per 2000 catalog) the above; plus 9:1 comp, vortec heads, 4 bolt, PM rods (5.7") hypereutectectic pistons, 3.80" stroke 4.00 bore. That would be great in our K5s. It might be availibew somewhere else, I just checked it out at work He said it was not produced. Send your hate mail to Joe"the parts guy" at my dealer.com

    Twiztid.com on G.M. put ot togather!
     
  8. lehtola

    lehtola 1/2 ton status

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    What about the LT4 with the eldebrock "multi-point EFI conversion system for TBI equipped 5.7 L chevy/GMC trucks"? Anyone running that system right now? Wouldn't it work well with the LT4?

    Priced at $1,195.95. Is it a waste of money?

    1990 GMC Jimmy 350/TH700R4/NP241/10 bolts, 4" skyjacker lift, 35x12.50R15 BFG All Terrains on 15x10 AR Baja's, Flowmasters.
     
  9. HarryH3

    HarryH3 1 ton status Author

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    That can probably be made to work, but again, it comes ready to run a stock 350, not a hopped up one. It would still require the proper programming to make it deliver enough fuel to put out 330 HP. Call Edelbrock's tech line, I'm sure that they can let you know if they can make it work.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  10. RESTORE89

    RESTORE89 1/2 ton status

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    would you have to change the whole puter or could you just get an upgraded chip? my motor is leakin burning and kind of getting week, and i was thinking of something in the 250-300hp range as a replacement, would this be feasible, and still use the stock tbi, and a custom chip. i have 10 bolts and a 208 so i dont want to much torque.
     
  11. HarryH3

    HarryH3 1 ton status Author

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    You just have to change the chip. You can keep your present computer. To get all the lowdown on your exact requirements you'll need to talk with a custom chip burner and provide them with all of your engine specs. Be sitting down when you call. The prices tend to run in the $350-500 range for totally custom chips. [​IMG]

    You can get lots of info about EFI from http://www.azspeed-marine.com
    http://www.fuelinjection.com

    You can also dig through <A target="_blank" HREF=http://www.corvetteforum.com>http://www.corvetteforum.com</A> for info on custom chip stuff.


    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     

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