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**NEW** Can OEM TBI Feed a 400??? ** NEW**

Discussion in 'The Garage' started by fad2blk99, Mar 19, 2004.

  1. fad2blk99

    fad2blk99 1/2 ton status

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    If I run a GMPP TBI/Vortec intake, Vortec heads, a Holley 670 TB (or maybe a 454 TB), high-pressure fuel pump, a TBI friendly cam, and a custom burned chip will my OEM TBI be up to the task?
    What do you guys (and gals) think? Have ya'll herd of anyone running this many cubes w/ a OEM TBI setup?
    Or should I bother w/ any of this crap and just slap on a carb? /forums/images/graemlins/dunno.gif /forums/images/graemlins/dunno.gif /forums/images/graemlins/dunno.gif

    ** UPDATE ** click here
     
  2. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Re: Can OEM TBI Feed a 400???

    It should work fine with a 454 tbi and custom chip. There is a guy or 2 on here with TBI 400's.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Can OEM TBI Feed a 400???

    No comment on anything other than the heads. With the TBI setup (or TPI for that matter) Vortec is about your worst possible choice.

    Pro-toplines, dart, world, whoever, all are better heads and most if not all can be had to use readily available (read=cheap) intakes, or the stock TBI intake.
     
  4. fad2blk99

    fad2blk99 1/2 ton status

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    Re: Can OEM TBI Feed a 400???

    Other than the bolt pattern problems, what's wrong with the Vortecs? CHP did an article on a 406 that made 500ft/lbs torque with Vortecs. And for $520/pr assenbled & brand new, there is no better cylinder head for the money, IMO. Similar heads from World cost a hundred + bucks more, which makes up for the Vortec intake (I would upgrade the intake either way).

    If you've herd bad stuff about the Vortecs let me know before I comiit to getting a set. /forums/images/graemlins/eek.gif
     
  5. azblazor

    azblazor 1/2 ton status Premium Member

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    Re: Can OEM TBI Feed a 400???

    My son runs a 400SBC with a stock 350TBI setup that we put on it. It runs excellent.
     
  6. fad2blk99

    fad2blk99 1/2 ton status

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    Re: Can OEM TBI Feed a 400???

    What kinda heads is he running?
    Is it a stock 400?
    /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif
     
  7. SUBFAN

    SUBFAN 1/2 ton status

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    Re: Can OEM TBI Feed a 400???

    More info please....I kave a 400 too that is just dying for a new home /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif
     
  8. mouse

    mouse 1/2 ton status

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    Re: Can OEM TBI Feed a 400???

    I'm helping a friend put together a 400 SB with Dart heads and a 350 TBI setup. The engine is going together in the next couple of weeks, and then we'll see if we can get it running. We have the entire wiring harness, serpentine belt system, distributor, etc. from a 1991 truck...
     
  9. HarryH3

    HarryH3 1 ton status Author

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    Re: Can OEM TBI Feed a 400???

    [ QUOTE ]
    My son runs a 400SBC with a stock 350TBI setup that we put on it. It runs excellent.

    [/ QUOTE ]
    Be careful! Many hopped up small blocks run "excellent" with the stock TBI, right up until the day that a piston gets a hole in it from running too lean. Ask dawson44 what happened to his. /forums/images/graemlins/frown.gif The stock injectors just can't supply enough fuel under high load conditions.
     
  10. azblazor

    azblazor 1/2 ton status Premium Member

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    Re: Can OEM TBI Feed a 400???

    It's not hopped up. It's a stock 400SBC. But it does well at all altitudes. Real time monitoring with an Auto-Xray shows a happy ECM with no sign of running lean.
     
  11. HarryH3

    HarryH3 1 ton status Author

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    Re: Can OEM TBI Feed a 400???

    The problem lies in the way that the ECM works. It totally ignores the O2 sensor at WOT, as the data it provides becomes invalid. It is possible for the ECM to adjust the injector pulse widths to compensate at part throttle. But most people never know there's a problem at WOT until it's too late. The only easy way to test what is going on at high RPM and high load conditions is with a (very expensive) wide band O2 sensor. /forums/images/graemlins/frown.gif The cheapest wide band O2 sensor diagnostic tool that I've seen costs around $400. /forums/images/graemlins/eek.gif
     
  12. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    Re: Can OEM TBI Feed a 400???

    [ QUOTE ]
    No comment on anything other than the heads. With the TBI setup (or TPI for that matter) Vortec is about your worst possible choice.

    Pro-toplines, dart, world, whoever, all are better heads and most if not all can be had to use readily available (read=cheap) intakes, or the stock TBI intake.

    [/ QUOTE ]
    i agree, and dyeager knows his shiz /forums/images/graemlins/waytogo.gif /forums/images/graemlins/wink.gif
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Can OEM TBI Feed a 400???

    OK, little late, but here goes. I should just save this stuff so I can copy and paste. /forums/images/graemlins/smile.gif

    Vortecs have pressed in studs. Not a real big deal, but aftermarket/high performance stuff is screw in. If I had a choice, screw in for sure. Used I'd be more concerned with this issue.

    Vortecs have 1.94/1.5 valves, period. You can have them reworked, but you are already adding cost at that point.

    Require rail rockers as shipped. With my roller cam, I spent a fair amount of time grinding the pushrod holes in the heads to clear. I like rail rockers, but using non-rail rockers isn't an option, at least not without additonal $$ on the heads.

    Vortec springs are good to about .450" lift, if you believe you need some valve spring retainer clearance at max lift.

    Vortec valve springs are weak, so better springs might be necessary depending on cam, etc. The cam manufacturer will let you know.

    Vortecs use special valve springs...either you machine the heads or buy special springs, of which there isn't much variety.

    Vortec's don't have provisions for EGR. (no crossover passage) If emissions is a concern, or you just want EGR (like me) you've got to plumb it externally. More $$

    Vortecs are thin castings. Not a concern for most people, but it IS something to think about. Don't 400's tend to run a little warm?

    Vortec injection intakes are about $3-400, and almost no selection.

    I don't think I've missed anything. If you can get by with completely bone stock Vortecs, and just add a TBI intake, you'll be looking at what, around $900? ($500 heads, $300 intake, $100 for shipping?) Not a bad price I guess, but again, potential extra expense you don't have to pay necessarily.

    BUT, if you do some research, and find another head that doesn't have the problems I've listed above, you can probably have a BETTER head, for the same overall money.

    It still requires research, there are a lot of variables, and I don't know ALL of them. The Vortec is a good design, but the combustion chamber itself is one of the main benefits, and most aftermarket heads have adopted that innnovation. Vortecs have great ports compared to earlier heads, but again, a set of aftermarkets should be just as "clean".

    I really liked the price I saw for the Pro-toplines on a post here on CK5, something like $500 complete. I only use those because thats a LOT cheaper than the $900-1000 the other aftermarket heads seem to run. BUT, you've got to make sure they have the '87+ intake bolt pattern, exhaust crossover, and so on.

    I guess my main advice is to spend a LOT of time researching...if you don't, what seems to be a good value early on, won't be, once you actually put money on it. /forums/images/graemlins/smile.gif
     
  14. fad2blk99

    fad2blk99 1/2 ton status

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    Re: Can OEM TBI Feed a 400???

    Dorian,
    Thanks for the info. I was aware of some of those issues but didn't think they would come into play in a low RPM, hi torque setup. Another thing that bothers me is the small combustion chambers. 64cc doesn't leave me w/ very good compression w/ stock pistons. And of course, I wanna run flat tops; so that'll leave me at around 10.9:1 /forums/images/graemlins/crazy.gif
    So what I'm saying is I think you may have broken me. I'm thinking about a set of 76cc World SR torquer's. But they run $760 assembled /forums/images/graemlins/eek.gif
    Who carries Pro-toplines?
     
  15. fad2blk99

    fad2blk99 1/2 ton status

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    Re: Can OEM TBI Feed a 400???

    [ QUOTE ]
    Be careful! Many hopped up small blocks run "excellent" with the stock TBI, right up until the day that a piston gets a hole in it from running too lean. Ask dawson44 what happened to his. /forums/images/graemlins/frown.gif The stock injectors just can't supply enough fuel under high load conditions.

    [/ QUOTE ]
    I had this happen w/ my bone stock '88 350 TBI.

    A 454 TB (or Holley 670), hi-pressure, fuel pump, and adjustable fuel pressure regulator wouldn't remidy this?
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Can OEM TBI Feed a 400???

    only post I could find about the pro-toplines being cheap, mentioned "midwest motorsports".

    Can't find the post with the link to the page that showed them.

    Are you building the motor from scratch? I purchased a set of speed-pro (not sure they even exist anymore) pistons for my motor, they are flat top hypereutectics, and they are designed with a 64CC chamber in mind, equaling about 9.2:1 compression. That is no problem with 87 octane and vortecs, FI will make it even less of a problem.

    I'm not totally "up" on my combustion theory, but I would imagine the smallest chamber possible with a flat top is your best power maker in a daily driver. If you can get pistons that will put you in the compression range you want, and still be flat tops, with 64CC chambers, that would probably be your best bet.
     
  17. SUBFAN

    SUBFAN 1/2 ton status

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    Re: Can OEM TBI Feed a 400???

    Small chambers with true reverse flat-tops is the ticket to lower compression (9-10:1) performance motors.

    Dart Pro Toplines have the more modern 'heart shaped' combustion chambers, where as the S/R Torquers do not....
     
  18. SUBFAN

    SUBFAN 1/2 ton status

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    Re: Can OEM TBI Feed a 400???

    I am watching this thread to see where it is going....

    I have a 400 sbc waiting to be rebuilt, but the induction problem is haunting me. I would like to retain the TBI system, but I do not feel comfortable with it's ability to properly feed this hungry mouse.

    I think Derf00 has the closest solution to this dilemna. He used an Edelbrock MPFI system on his 383 with a chip Edelbrock supplied him.

    I have not convinced myself that this will keep the extra 23 cubic inches happy /forums/images/graemlins/dunno.gif (.030 overbore, for you math gurus)

    Lets hear from more peeps that have DONE this, and get more information on their motor, like cam specs and such, as this will be an important aspect in the deciding factor.... /forums/images/graemlins/thinking.gif
     
  19. jakesdad

    jakesdad Registered Member

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    Re: Can OEM TBI Feed a 400???

    I'm running a .040 over 400 with early 350 heads (non-vortec) and TBI. I'm using an Edelbrock performer intake, with a TBI adaptor plate from Summit, which conveniently has 2" bores, and a 454 TBI unit. I converted the pressure regulator so it is adjustable, and turned the pressure DOWN to about 8 psi. that gives me about 73lb/hr from the 454's 90lb/hr injectors (350 TBI injectors are 55lb/hr). The injectors still have a good spray pattern, and in closed loop the LTMs stay around 128. As said in one of the posts above, the issue is really at WOT (in power enrichment) when the O2 sensor signal isn't used for fueling. The big injectors and the adjustable regulator do the trick. I've got over 60K on this combo. I just wanted to throw in 2 more cents.
     
  20. fad2blk99

    fad2blk99 1/2 ton status

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    Re: Can OEM TBI Feed a 400???

    I'll definitely be checking w/ you when I go w/ my 400/TBI setup! /forums/images/graemlins/thumb.gif But, @ .040 over on a 400sbc... aren't you on barrowed time? /forums/images/graemlins/eek.gif From what I've researched, anything over .030 over and the cylinders want to become one... Nevertheless, if you got 60k + on the setup, I guess that’ll dispel that myth. /forums/images/graemlins/wink.gif

    Dorian… from my research on pistons, flat-tops yield the most efficient combustion, as you get a more even burn across a flat top than you would a dish or dome. /forums/images/graemlins/thinking.gif The later two are only used in lieu of the flat top to raise or increase compression to desired specs.

    As for the heart shaped quench / combustion chamber heads… GM seams to have had great success with this setup in their vortec and aluminum “fast burn” heads. If I can, I’d like to get a set of heads utilizing this technology, but since they changed their intake bolt pattern …. plus the low 64 cc chambers… you get the idea… (Bastards!!!! /forums/images/graemlins/angryfire.gif /forums/images/graemlins/angryfire.gif /forums/images/graemlins/angryfire.gif)
     

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