Will mine run it?

[VorTecxas]

I know they're crap, but will my '96 blackbox for my 5.7 temporarily run the stock '98 7.4 that I'm swapping in without any tuning/modification (plug and go)? I have the PCM from the Suburban but I've heard you have to disable the VATS before it will run, if I don't have to then I'll just use that one for now.

This is my daily and the ol' 350 is knocking like a Jehovas Witness. I already have the 7.4 out of the 'Burban (engine/trans/harness) ready to swap in, but I don't have time or money at the moment to send anything in to get tuned before I need to do this swap. I do plan on sending in the 411 I have to get tuned, but again, do not have time or money right now and I have to get this thing running ASAP.

NOT to be rude, but please do not point out the obvious. I know I have to use the 7.4 harness and I know the blackbox sucks.

Thanks

 

[frito-bandito]

Sorry man I really don't know, but I had to at " a 5.7 knocking like a jehovas witness"

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[Aloicious]

no, it will not work without tuning, and even if you got it to wire up, without tuning the PCM is going to be expecting to fuel a 5.7, not a 7.4, so you'd run into severe fueling and other problems...

the '96 PCM will be a 5 plug PCM, the '98 will be a 4 plug PCM, you mentioned using the 7.4 harness, so if you're doing that, you'll be able to plug in the '98 pcm, you might be able to run that (assuming the Transmissions are the same in the 2 vehicles, however with the 7.4 I'm guessing they might not be, probably a 60e in the '96 and an 80e in the '98 is what I would guess) I'm not sure on the VATS situation with a '98 PCM, you might not have any VATS issues, but I'm not 100% sure...

really there isn't much way of doing an engine swap like that without needing some kind of tuning. but your best bet will be to use the '98 PCM with the '98 454...IF the trucks ran the same transmission (or if you're also swapping the 454 transmission too)...

 

[VorTecxas]

Swapping trans too. I have both trucks. Also something I didn't think about. The Suburban (454) is a California truck with a smog pump. I want to delete that. Again, until I can get the tune done, will it hurt anything (besides setting the CEL off) to go ahead and remove all of that? And I have a whole other harness and PCM that is non-A.I.R if I can just use that. All I have to do is remove the system, plug anything that will cause a vac/exhaust leak, and get a tensioner for a non A.I.R truck.

 

[VorTecxas]

And as far as the fueling, I thought the factory 454 injectors were the same as the 350, 19lbs/hr?

 

[Aloicious]

yeah injectors are probably similar, but I was refering to airflow, the calculations for injector pulse widths will be vastly different on a 7.4 vs a 5.7...things like the VE table will be different, etc...there's alot more that goes into fueling from the PCM than just the injector sizing. not to mention that unless I'm mistaken the 7.4 used real injectors, not the spider POS that the 5.7 used, so the injector charactoristics and dynamics will be alot different..

removing the AIR pump will probably cause a SES light, but shouldn't be much of a problem otherwise.

if you're swapping the 98 engine/trans/harness, just use the 98 pcm, thats the way to go. your only potential problem there (that I can think of) would be the security, which may not even be a problem. and possibly a incorrect speedometer if the gearing is different on the '96...

 

[VorTecxas]

Good point with the fueling. I'm just so focused on swapping this thing I didn't even consider the differences, I'm just thinking "Air, Fuel, Spark, Control". Not necessarily the specifics of it.

As far as the PCM, I was thinking that the non-A.I.R one that I have from another 454 (it's also a '98) wouldn't have the settings for the smog pump and would avoid the SES light when I leave all of that unplugged. I'm not real worried about the light, I just don't like it on, makes anyone looking at it think somethings wrong.

 

[VorTecxas]

Sorry man I really don't know, but I had to at " a 5.7 knocking like a jehovas witness"

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Yeah I made my buddy spew Miller Lite out of his nose when I first used that one haha

 

[VorTecxas]

BTW Aloicious, do you happen to know the max factory airflow CFM for that L29?

 

[frito-bandito]

Yeah I made my buddy spew Miller Lite out of his nose when I first used that one haha

That sir definitely deserves some REP!!!!

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