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What kind of vacume are you running on your TBI?

Discussion in 'The Garage' started by Shagnaz, Jun 22, 2004.

  1. Shagnaz

    Shagnaz 1/2 ton status

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    Just wondering? I have 15in lbs. with the RV cam.

    Thanks
     
  2. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    I've got 15in with my carb setup and comp cam 268H.
     
  3. Shagnaz

    Shagnaz 1/2 ton status

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    Thanks for the reply, but I need vacume from a TBI motor w/ rv cam.
    Thanks
     
  4. fortcollinsram

    fortcollinsram 1/2 ton status

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    My TBI 454 has 18inHg at idle with a crane 2020 cam,

    Chris
     
  5. FWP

    FWP CRS

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    350/ mild Elgin Cam...14" Hg... I'm also at 5000' elevation
     
  6. bigburban383

    bigburban383 1/2 ton status

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    Yeah, about 15 in too with a 350 TBI unit. Its a 388 stroker 214/224 with .455/.464 lift TBI cam.
     
  7. Shagnaz

    Shagnaz 1/2 ton status

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    What did you guys do to get the motor to run decent? Mine is running rich.
     
  8. chevyjeff

    chevyjeff 1/2 ton status

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    did you ever try the heated o2 sensor?
     
  9. fortcollinsram

    fortcollinsram 1/2 ton status

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    [ QUOTE ]
    What did you guys do to get the motor to run decent? Mine is running rich.

    [/ QUOTE ]

    put it together, added an vacuum referenced fuel pressure regulator, set the timing at 6* and ran it...

    Seriously though, what mods have you done to the motor?

    Chris
     
  10. Shagnaz

    Shagnaz 1/2 ton status

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    I haven't tried the heated O2. Dawson (I think his user name is Dawson444) said he didn't have to do it. The motor that was in there ran fine, but had high miles and I believe the cam lobes were nearly round.
     
  11. Shagnaz

    Shagnaz 1/2 ton status

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    The motor is a 84 vette that has been bore .30, so now it's a 355 with regular flat top pistons 9.5 to 1 compression. The cam is suppose to be a computer cam. I thought I was having problems with the TPS, so I got a Holley 670 TBI unit and now it breaks up @ 2500 rpm. It pulls good, but then it fells like it gets bogged down.
    Where did you get the vacume ref fuel reg? I have seen them, but can't find where to pick one up.
    I have another 670 Holley with an adjustable reg on it. Thought about putting that on it. Then, have a friend hold it at 2500 rpm and back the fuel press. off some.
    Do you think I should put a air/fuel meter on the O2 to see what is going on?
    I have been so disappointed with the whole thing, that I have been letting it sit. I am going to work on it tonight and try the other fuel reg. If I can't figure anything out, I'm just going to put a 600 carb with a HEI distrib in it. I'm not going to get rid of the FI, just tie it up and out of the way.
    Can you suggest anything?
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Sounds like you need to get a scanner on it. Ignition problems could be the culprit, or, if you are running old style heads, you very well could be seeing a lot of knock and the EFI is retarding timing.

    9.5:1 on old school heads even with EFI is likely detonation city. Sorry if I missed anything regarding to the engine specs.
     
  13. Shagnaz

    Shagnaz 1/2 ton status

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    That is the problem. Messed around with the truck on Sat. and found that the timing is set good. When the truck runs good the timing is staying put, but then the truck starts to act up, the timing is way retarded.

    Any suggestion before I rip all the EFI off and go to a carb?

    HELP /forums/images/graemlins/confused.gif

    Thanks
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    Get better heads?

    Ripping the EFI off really isn't a good solution, you still have too much compression with crappy heads, IF that is indeed why your timing is being retarded. If that is why it' s happening, the EFI is SAVING that engine.

    I guess dumping more fuel in would hide the problem, (run a carb rich) but it's definitely not a solution.
     
  15. Shagnaz

    Shagnaz 1/2 ton status

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    9.5 to not high compression. My orginal motor had 280,000 on it and it ran ok, but had no real "nuts" to it. This motor is very mild to stock. Nothing radical at all.
    Why would the heads be the problem...please explain
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    Stock 350's in the 80's were running about 8:1 CR.

    305's were running 9.2:1 at the same time, and the ESC system, (spark control, to retard timing when knock was sensed) to keep the engines from killing themselves, because they were obviously on the ragged edge.

    I would *think* that higher octane gas should have eliminated the problem you are experiencing though.

    The combustion chamber of the older heads sucks. They are not efficient.

    There are two reasons new motors are running 9:1+ on 87 octane: EFI, and better combustion chambers. Vortecs for instance, need and respond better to less timing than older head designs.

    Was the original engine a 350 as well? Just wondering since the ESC module (if TBI ESC is standalone your year) and knock sensor are different between 305 and 350.
     

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