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TBI or TPI

Discussion in 'The Garage' started by big83chevy4x4, Aug 14, 2005.

  1. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    i have a chance of buying a complete TPI setup for $400 from a guy at work.

    i have been planning on going TBI for a while and know where i can get the stuff for a good price.

    i have a 355 with flattops, comp XE262H cam, with headers

    what would go with and why?
     
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    TPI is far superior to TBI. More HP and torque can be made from a TPI setup and you get better fuel distribution with TPI since it is direct port injected and not centrally distributed like a TBI.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    TPI, as long as it's complete and for a 350!

    Missing/broken/incorrect pieces will cost you trying to get a "complete" setup put together.
     
  4. Blue85

    Blue85 Troll Premium Member

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    You know you want TPI. :D

    You might check with some chip burners right now, give them your engine specs and make sure that you can get a good running setup with either one. You should also find out if the injectors are good and if they will work with your engine.

    There are two main types of TPI systems, from 85-89 was the MAF and 90-93 was the MAP type (speed density). Those years may not be exact and the Corvette systems were sometimes different than the others. There are a lot of systems floating around from 305s, but you want a system for a 350 (I think).

    Either way, you'll want to get an in-tank fuel pump and add a fuel return line. The TPI needs a lot more fuel pressure than the TBI.

    There are a lot of good sites with TPI information, but I haven't seen many covering TBI. The TBI should be a much easier conversion.
     
  5. K5Steve

    K5Steve 1/2 ton status

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    Any tpi setup will work.The only thing different from 305 and 350 was the chip.The computers are the same also,just make sure you get a 350 chip and you'll be good.I am going to do this swap also,being a thirdgen trans am and camaro fan I Have picked up quite a bit of knowledge about tpi.You caould visit Thirdgen.org for all your tpi/tbi needs.You can also visit http://www.tpiparts.net/
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    It isn't just the chip.

    I know it's been covered before, but in case anyone new is reading:

    You've got different injectors, knock sensor, ESC module (not a factor on the '90+ setups) and the PROM of course between 305 and 350. 305 PROM isn't that big a deal for a 350, but if getting stuff from a donor, it's easiest/cheaper to get it all from one vehicle, and with the "right" displacement as well.

    The wiring itself is also slightly different. Compare VIN F with VIN 8 (305 vs. 350) wiring and you'll notice that wire color is different for certain circuits, which can lead to confusion. No problem if you know what VIN harness you have, and if you have the right year wiring diagrams though, which are a necessity.

    Sure, you can do an aftermarket harness, but a good donor will provide the stock harness, which is perhaps slightly more difficult to deal with than aftermarket. It will however, keep cost down a fair amount.

    My opinion, (and the way I should have done it) if not changing the short block, is to get the heads from a donor as the L98's are better than truck heads. If you aren't getting heads from the donor, and are going to keep your stock truck heads that have the older intake bolt pattern, look for an '85-86 TPI base, and the runners/plenum from '89+, to get rid of the cold start injector. You don't want the '85 TPI setup itself though, the MAF stuff is done differently than other years and is inferior.

    '89+ stuff will HAVE to have a new PROM burned to even start the thing, as VATS is active in all '89+ TPI PROM's.

    Lots of options just among TPI components, but if it were I, I'd go MAP and newer heads that allow the stock TPI base to bolt to them.

    thirdgen.org has a pretty decent classified section, lots of parts show up there.

    edit: oh yeah, and to get everything optimal, you'll need to burn chips, either yourself or have someone do it. Doing it yourself is really the only way to get it perfect, you can read all about that on here and thirdgen.org's forums.
     
  7. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    I have my tpi on basically the same engine combo (flat tops, XE262H) I'll be firing it up this week, and I can tell you how a MAF (86 setup) TPI works with it :)
     
  8. K5Steve

    K5Steve 1/2 ton status

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    I figured they knew the injectors would be different.I spaced the knock sensor and esc,sorry.Look for aluminum l98 heads if you can,they came on the corvettes.They are harder to find though as there are a lot more t/a's and camaros floating around.Some tpi's also has the small cap distributor with a remote mount coil.
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    I just put the info out to reiterate what is known by some but not others. When talking about injection swaps, there are enough differences out there that people can get into trouble, or suckered into getting parts they can't use or end up changing later.

    There are a few that have done the TPI conversion, and the experiences of most of them (us I guess lol) will hopefully help people considering the swap make an informed decision and get a good setup right off the bat. Saves a lot of time hassle and money.

    All the computer cams offered by comp that I see use a lobe seperation of 112*-114*, and that's pretty important, especially so in MAP applications. The 262H mentioned is 110*.

    I can tell you that a much more "mild" cam (Crane HR 260-2-12) in my MAF setup results in surging idle when cold, and some other issues. Of course, an engine is a system, so my changing heads, compression, exhaust, and everything else is affecting how it runs.

    A simple change to a later PROM (1989 'vette) made it run a whole lot better, but there is still a lot to do in the PROM to get the setup running as it should.
     
  10. Cmoe

    Cmoe 1/2 ton status

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    You may have to have some Mill work done on the center holes of the TPI intake depending on what year the doner was. Would you get the wiring harness and computer, exc.

    I would love to have a TPI system
     
  11. K5Steve

    K5Steve 1/2 ton status

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    If you have vortec heads you would need to get a base from Skoggin dickie performance.
     
  12. big94gmc

    big94gmc 1/2 ton status

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  13. hi pinion

    hi pinion 3/4 ton status

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    Actually, there are only a few disussions about TPI coversions,,,,on 80s blazers especially, as a matter of fact, since ive been here , there have only been 2 that i have seen, completed, Ryan b. (first geb) and, tunedport k5. I say keep the discussions flowing, the more the better. :thumb:
     
  14. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    he has two complete setups, oen he is keeping and one he is selling. they are both off 350 corvettes. one has the cold start and the other doesn't. other than that i know nothing, but i can ask him.

    i know alot more about the TBI that the TPI.
     
  15. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Hopefully you can make that three if I ever manage to get my fuel lines plumbed up, lol! I cannot seem to come home with the right parts the first time, ever! :haha:
     
  16. HarryH3

    HarryH3 1 ton status Author

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    I guess you've never visited the link in my sig... :rolleyes: I TPI'd my '75 way back in 1989. :cool1:
     
  17. hi pinion

    hi pinion 3/4 ton status

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    Um harry, i think i was still in highschool then lol :haha:
     

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