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  1. S

    99 L29 454 build

    Extreme, the pressure in the manifold is almost always less than ambient. The vacuum level is typically about 15 inches at idle to 24 inches when coasting down. (29 inches is absolute vacuum). The only time manifold pressure approaches atmospheric is at wot when air flows in with minimum...
  2. S

    99 L29 454 build

    Thanks Mang! (See what I did there?) That is so true about the intake. Go back to post 44 of this thread, where I drilled the manifold and put a thermocouple probe into the number 2 cylinder runner. Air going into the head was at the full temperature of the engine, 190+. More throttle didn't...
  3. S

    99 L29 454 build

    Ok thanks. That's great as long as it can do the obvious, which is reduce timing as engine load and cylinder pressure goes up. I trust they will get it right this time. If not, can I send it to you L31? I just thought of something. The egr is turned off in the tune. Could they be forgetting to...
  4. S

    99 L29 454 build

    I'm on something like the 8th trip back up to the tuner. Besides still pinging at wot, it audibly and steadily pings at hway speed 55-65 climbing slight hills, when rolling into the throttle in 3rd and 4th gear, and at 30-40% throttle accelerating through the gears. So I asked them to reduce wot...
  5. S

    Another 454 Vortec Build Thread - Documenting, Q&A, Help

    How's the compression? No sense worrying about injectors if it's not healthy.
  6. S

    Another 454 Vortec Build Thread - Documenting, Q&A, Help

    Ok I see, yes I was trying to say fuel tank pressure sensor, which is what I though OP was asking about.
  7. S

    Another 454 Vortec Build Thread - Documenting, Q&A, Help

    Here is the full page. FPS started in 98. And I don't know if this is relevant to what you were saying.
  8. S

    Another 454 Vortec Build Thread - Documenting, Q&A, Help

    Ok, I am trying to understand. You said this: I posted page from the 98 c/k service manual, showing the ftp circuit on the 7.4L engine, so it has to be a 2500/3500. Edit - I see the top of the page that said 7.4l was cut off, sorry.
  9. S

    Another 454 Vortec Build Thread - Documenting, Q&A, Help

    "Yeah, I'm going to have to go ahead and disagree with ya there..." 1998 c/k factory service manual:
  10. S

    Another 454 Vortec Build Thread - Documenting, Q&A, Help

    Super, I think they started using a fuel pressure sensor starting in 98. It was an option for me to wire in with the 0411 swap.
  11. S

    Another 454 Vortec Build Thread - Documenting, Q&A, Help

    Bex, how long should the stock rail and regulator hold pressure? My Holley aftermarket fpr bleeds down pretty fast, but I don't think it hurts anything, as it goes immediately to full pressure when I hit the key.
  12. S

    Another 454 Vortec Build Thread - Documenting, Q&A, Help

    How bad is the gas? I would siphon it all out.
  13. S

    6.5 to 454 vortec swap

    Isn't the pushbutton 4wd on 1/2 ton only?
  14. S

    6.5 to 454 vortec swap

    You will want to swap in the L29's complete wiring harness and ecm. It's completely different from the throttle body wiring. You should consider doing the 0411 ecm swap too. It's a lot of work, but worth it if you have the time. I found burned wires in a couple places on mine, that I never would...
  15. S

    6.5 to 454 vortec swap

    3/4T suburbans are cool, especially when they have the 14 bolt full floater axle. Maybe leave it alone and find another engine/trans.
  16. S

    Another 454 Vortec Build Thread - Documenting, Q&A, Help

    This guy Tolman has a lot of great vids on upgrading the Gmt400 trucks. This 0411 swap vid convinced me to make the jump. But I went way further and basically reran every wire from ecm to sensor. I was having strange problems with the 4wd, and it turned out to be wires burned up from exhaust...
  17. S

    The Official Vortec 454 Info thread

    Looks like it spent 20 years in Redneckistan.. It stops? Someone started a disk brake conversion on the right rear but didn't finish. Brake line is disconnected. Most cheap/easy disk conversions lose your parking brake, but good kits that use modern oem parts are out there. Purging and bleeding...
  18. S

    Vacuum canister

    Who do I bill for the 5 1/2 minutes I just wasted?
  19. S

    99 L29 454 build

    So that screen shot shows the afr at 14.18 all the way across except at wot. That's not right is it?
  20. S

    99 L29 454 build

    What is PE? power enrichment? Open loop?
  21. S

    99 L29 454 build

    Ok thanks! The latest tune came back last week. They reduced wot timing to 22-24deg and kept the cruise part throttle timing up where it belongs. Fuel trims are down to 1-2 percent, so they figured out the injectors, finally after 6 adjustments. There are strange glitches all over the chart. AFR...
  22. S

    Lifter Recomendations For Cam Setup

    I wonder if that's a problem on the L29 big block. I have a persistent valvetrain noise that I can't figure out, running low mile stock l29 lifters on a comp cam 08-411. But it doesn't seem to be getting worse.
  23. S

    Lifter Recomendations For Cam Setup

    The stock lifters are limited on lift before they run into the stock dog bone retainers. Make sure any aftermarket replacements can handle the lift of your cam.
  24. S

    12200411 PCM swap for 1996 to 2000 GMT400 trucks

    two threads down https://www.gmt400.com/threads/0411-pinout-contact-for-lextech.61796/
  25. S

    New member. New tune. Blown engine.

    I downloaded it and tried, but my efi live scan app said it's not a valid efi live file.

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