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TBI performance

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by NE-RokToy, May 13, 2003.

  1. NE-RokToy

    NE-RokToy Registered Member

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    Ok long story short my 88 GMC 350 is dead, going to spend the time to rebuild it right and want to know how much I can achieve and keep the TBI. I really don't want a different computer system but would go for a custom burnt chip and upgraded parts if they arent to expensive. I was thinking rebuild, the right cam, a set of vortec heads (they make a TBI intake for vortec heads right) and headers plus whatever I need to do to the fuel system. Am I stupid for wanting a little over 300 hp with TBI??? Help me out please!
     
  2. rick88blaze

    rick88blaze 1/2 ton status

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    yes, there is a vortec intake for a TBI, it's about $300 from GM. also you could upgrade your TBI from stock to a holley one. it'll be about another $300 for so.
     
  3. DukeBoy88

    DukeBoy88 1/2 ton status

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    300+ hp with TBI is very doable. check out turbocity.com they have lots of info for upgrading TBI. I purchased the holley 670cfm TB and plan to put it on a HT383, but the engine portion of my rebuild isn't for awhile yet. I'm going to make an adapter instead of using a TB intake, I'd like to use an RPM air gap manifold and I haven't found a TB version of it for vortec heads. I planned on using Ed Wrights programing for the chip. good luck /forums/images/graemlins/thumb.gif
     
  4. 88Silverado

    88Silverado 1/2 ton status

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  5. Thunder

    Thunder 3/4 ton status

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    Here's the links toturbocity.com
    I'v used a lot of their stuff it works pretty good. They can also burn you a custom chip. Call or Email them tell them what you want to do they can make recomendations to what you may need.
    http://www.fastchip.comAlso does good chip work
    Their stage 2 chip will probabally work for your needs(depending on mods) if you keep the HP around the 300 HP range without the cost of a custom chip

    Both Crane and Comp cams make good computer grind cams that will work good with stock and aftermarket chips. You can usually use cams with durations up to 214 degrees and lifts .480" @ .050 without getting a custom chip burned.
    Keep the compression ratio down around 9 or 9.5 to 1 and you shouldn't have any issues with the chip programing.
    You can get the Vortec to TBI manifold from most GM dealers. Its a GMPP product.You will also need the EGR plumbing.
    That should get you to around 300 hp no problem.
    I think the stock TBI is rated for somewhere around 300 fuel HP but that is only numbers and theroy. Real life will probabally be lower. So a TB with a little better flow would not hurt. I like turbocitys TBs because they are stock units. I have never really liked Holley FI stuff but i have heard it has improved a lot lately
    Heres a link to some high performance crate TBI engines this may give you some ideas they also sell the manifold you need.
    sdpc2000.com
    Hope this helps.
     
  6. scrappy88

    scrappy88 1/2 ton status

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    I'd recommend going with a Turbo City throttle body over the Holley replacement. The Holley flows well but their injectors are garbage. I had one and was not impressed. Swapped to a Turbo City one, very nice and it uses your stock injectors, or you can upgrade to the flow matched injectors from them as well.
     
  7. BrianDamage

    BrianDamage 1/2 ton status

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    edelbrock has a deal where if you buy the heads, cam & intake form them, they will give you a free chip

    you don't even have to buy them all at the same time
     
  8. NE-RokToy

    NE-RokToy Registered Member

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    Wow thanks for all the Quick relplies! Looks like my goal will be easier then though, and won't cost much more then going with a carb!
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    I was going to say look into aftermarket heads, and you can reuse your intake, but I've never looked at a TBI intake. Are the ports any smaller than other SBC intake ports, or is all the "restriction" in the TBI heads?

    The Vortec heads, plus intake, plus valvetrain mods if you go much over .450" lift on the cam, will put the cost up around what aftermarket heads will cost. That is assuming that your TBI intake isn't super restrictive. Point being, if you buy heads that allow you to re-use the stock TBI intake, you'll have $300 "extra" dollars to play around with.
     
  10. NE-RokToy

    NE-RokToy Registered Member

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    I plan on replacing the intake so the vortec heads really are no extra cost (the edelbrock intake is about $40 more) and I plan on keeping the cam relativly mild. Also vortec heads seem to be much cheaper then any comparable aftermarket head.

    Ok so here are my plans:

    -rebuilt short block with 9.35:1 hypereutectic pistons
    -vortec heads
    -Lunati cam, 204/216 @ .050", .427/.454 lift
    -still debating which intake
    -turbo city throttle body and injectors
    -headers (need to find a set for 88 GMC jimmy)
    -single 3" exhaust with hooker muffler
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    Why replace the intake if theres nothing wrong with it? Like I said, I don't know if there is anything wrong with the TBI intakes, hoping someone could answer that knew, but port velocity is a good thing for torque, and that cam you've got picked out is going to make a lot of low end torque.

    You'll need to check with the cam company, as the stock Vortec springs may not be up to the task. They weren't for mine, but I've got a roller cam.

    As someone suggested, you might check with the Edelbrock package deal. Doubt the chip is worth anything, but the other stuff may be what you are looking for.
     
  12. 88Silverado

    88Silverado 1/2 ton status

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    If he's switching to the Vortec heads he must get a different intake manifold. The bolt pattern is different from standard chevy heads.
    Standard GM TBI intakes are very restrictive. They have very small ports and short runners. Its best to go to a 4BBL type and use the adaptor, this gives you less restrictions, higher plenum and longer runners. GM never made a performance TBI intake that im aware of.

    The combo sounds good and should be pretty mild and reliable.
     
  13. BayouBlazer88

    BayouBlazer88 1/2 ton status

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    how about buying the holley tbi and replacing the injectors with turbocity injectors?
     
  14. fortcollinsram

    fortcollinsram 1/2 ton status

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    Or get yourself a 454 TBI, (talk to the gang over at www.454ss.com to learn what you can do to it to really make it flow) A stock 454 TBI will flow just as much as the modified 350 unit, as it has 2" bores. Just bore the 350 intake mannie holes a bit bigger...you can get even more flow by using an injector spacer (usually oe on many later model 454 TB's) shaved throttle shaft and TB spacer...Some of those 454 guys are supporting over 400 hp with a lightly modded TB...def. get the JET Fuel Press. Reg. much higher quality than the Turbo city unit (which just mods the stock unit)
     
  15. scrappy88

    scrappy88 1/2 ton status

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    Actually I saw one on Ebay a while back that someone did that with. Holley TBI with a GM injector pod. Best of both! /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif
     
  16. Thunder

    Thunder 3/4 ton status

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    I'll add 1 more thing for you to think about.
    If you go with a set of WORLD S/R centerbolt Torquer heads.Instead of Vortecs
    You wont need a $350.00 TBI/vortec manifold and dont have to worry about running too big of a lift cam for the vortecs. with vortec you have to make sure the valve wont hit the piston if you go with much over a stock cam. Espically if you have to get the block decked. That .054 exhaust lift is right on the border line. There are coil binding issues as well.
    The World heads cost about the same as buying the Vortec heads and manifold. They are a direct bolt on They also flow better than vortec. Power gains are similar. They come set up to handle high lift cams up to .560 lift

    Also I think those 9.35 to 1 pistons are too much.
    Just putting on the Vortec heads will raise the compression ratio to that level+. You may have valve to piston clearance problems. with those pistons Vortecs have 64cc chambers VS 76cc chambers in the stock TBI heads

    Those pistons would work great with the 76cc World heads /forums/images/graemlins/thumb.gif
    http://www.worldcastings.com/
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    [ QUOTE ]
    If he's switching to the Vortec heads he must get a different intake manifold. The bolt pattern is different from standard chevy heads.

    [/ QUOTE ]

    The intake ports are also raised, and you'd have port mismatch. Why buy heads that force you to replace the intake when you can buy heads that are just as good, if not better, and let you keep the stock intake?

    [ QUOTE ]
    Standard GM TBI intakes are very restrictive. They have very small ports and short runners.

    [/ QUOTE ]

    So TBI intakes use a different port size than non-TBI chevs? Short runners don't hurt anything either, and since the intake isn't much different in design than the carbed ones, runner length isn't much of an issue either. The TBI heads are more of a restriction than the intake is, and with the newer chamber designs, even if you don't increase intake flow, you still gain over stock heads.
     
  18. BayouBlazer88

    BayouBlazer88 1/2 ton status

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    Where do you get a tbi adapter plate for a 4bl intake? I lookeed all over turbocity and I cant seem to find it.
     
  19. Thunder

    Thunder 3/4 ton status

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    Call or Email turbocity for the adapter. They have tons of stuff they dont show on their web site. They sell everything related to TBI, sensors, adapters,chips ecm, ect, ect. They have a 4 page catalog just for TBI. At pretty good prices too. /forums/images/graemlins/thumb.gif
     
  20. 88Silverado

    88Silverado 1/2 ton status

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    The openings in the stock TBI's are fairly small diameter. A larger TBI setup wont mate properly.

    I agree, for a few penny's more the World S/R are a better setup with more potential and keeping closer to "Generic" GM or aftermarket parts. The Vortec heads are also thin and I have seen 2 sets with cracks.
     

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