Stick with TBI or convert to OBD2 (Vortec/CSFI)

It's been quite a while since I last posted, so I'll summarize where I'm at.

- '91 3/4T 4x4 suburban, 383 stroker, vortec heads and stock vortec roller valve train/cam
- 46mm TB, 454 injectors (I think they're 74lbs), modified adj fuel press regulator, set at 13 psi
- GM 4-barrel intake for vortec with TBI adapter plate
- Stock 4L80e trans. (91 3/4 ton burbs and 1 ton crew cabs only square body trucks to ever get a L80)

Here's the rub. 91-93 trucks with 4L80e used a '7060 PCM which is an enigma. It's hard to tune, very few hacks available, and no available input for a WB O2. I've worked on it for a long time and I don't think it's going to get much better. Dave W and others have suggested I go to a '7427 since there's so much more support for them. Good idea, but the 91-93 4L80e needs a '7060 due to a cleaning cycle that is PCM controlled. UNLESS......

I have an apt scheduled with a reputable trans shop that knows how to mod the old 4L80e to use a newer PCM. (Metro Trans, Woodland, WA - recommended by Dave W) They're going to change the force motor and do a few other things, including a shift kit. Once that's done, I have a few more options.

Most likely will stick with TBI and just upgrade to a '7427 PCM. Take advantage of additional bins and masks, etc. But I keep having this idea of getting a junkyard CSFI system from a '96-'99 350 truck swapping it over. I know I'd need the PCM, harness, all emissions and sensors, etc. Might even buy a complete truck and part it out - sell what I don't need. I also know I'd need to update the stock spider assembly, unless it's already been done.

Is this a dumb idea? Should I forget about it? Any easier ways to get to OBD2? I just thought it might be worth it since I already have vortec heads and the CSFI manifold will bolt on. There's another wrinkle too: I need to pull the existing intake. It's burning oil after idling for a while, but compression is good, so I'm hoping it's a bad intake gasket.

The 16197427 can operate 8 injectors when the 16197427 is converted to MPFI mode.

dave w

the "blackbox" pcm is limited to what you can tune, and not a lot of support. fast355 can probably offer you more technical info but he upgraded his vortec system to a LS '411 PCM. I believe you have to source a marine vortec intake as it uses "real" injectors OR add injector bungs to your current intake. then repin the Blackbox ends to newer LS style pcm connectors. keep in mind now tuning costs go WAY up.

im working on making that blackbox ecm practically free to tune .... i have one for testing, but it'll be a while before i finish because the weather is really nice and i dont want to just sit in the basement

Quote:

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Originally Posted by dave w

The 16197427 can operate 8 injectors when the 16197427 is converted to MPFI mode.

dave w

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This is great news, Dave. Thanks much for the info and the zip file, lots of good info. I think I may go ahead and get a '7427 now since I can start out with all my TBI stuff and eventually switch over to the vortec.

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Originally Posted by steveo

im working on making that blackbox ecm practically free to tune .... i have one for testing, but it'll be a while before i finish because the weather is really nice and i dont want to just sit in the basement

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Cool! When you guys say the "blackbox" is the PCM for the vortec CSFI setup you're talking about? I'll stay tuned for progress. Enjoy the weather, I have the same thoughts.

Quote:

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Originally Posted by Daveo91

Cool! When you guys say the "blackbox" is the PCM for the vortec CSFI setup you're talking about? I'll stay tuned for progress. Enjoy the weather, I have the same thoughts.

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For a Vortec 350 the black box ran 96-2000. 0411 ran 01-02. Green/Blue connector ran 03+

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Originally Posted by Fast355

For a Vortec 350 the black box ran 96-2000. 0411 ran 01-02. Green/Blue connector ran 03+

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Thanks!

UPDATE: I am now the proud owner of a '97 3/4 ton burb, stock 350 vortec, 4L80e trans. I bought it at auction for $375 (although the stupid fees were substantially higher than that) Engine runs, but barely. I think the flex plate is busted or maybe a bolt is backed out and clanking on something. I got it running just enough to get it up my steep driveway into my shop. And that's OK - it will never run again under its own power. So my plan is to keep the EFI, computer, harness, other wiring parts, trans and part out most of the rest of it. I've not decided for sure yet, but I may spend my money having that trans gone thru rather than my original '91 80e. That way I'm guaranteed to be rid of the worry about the Bosch force motor and it's weird cleaning cycle. But again, not sure - I'd have to reroute cooler lines and learn how to get the linkage to work between the '97 trans and '91 burb.

Back to the EFI question: so my 383 is basically stock vortec, other than the 33 extra cubes. (Well I guess CR is a little higher - 9.5:1). Wouldn't the black box just learn the differences and compensate? The reason I'm asking is the description for the GM crate HT383 says it is designed for direct replacement for a vortec 350, and the computer will learn the differences without a tune needed. So if I'm happy with stock tune, COULD I use the black box and full EFI from the '97? I just purchased a '7427 and starter chip tune from Dave W for the TBI, so I'm going to start with that and it may be that I just keep it, especially if I eventually convert to MPFI with it. But just want to know what my options are.