1990 c3500 350 to 454 swap

[MisterGrimm]

Hello all! First time poster. Long time lurker. Signed up for the forum for the wisdom that only y'all can provide.

A couple of years ago I purchased a 1990 C3500. I love the truck. It came to me equipped with a TBI 350, but the vin indicated that it was born with a 454. I figured that eventually I'd swap a BBC back in there when I came about a good motor. Fast forward to now, and I've had a 454 built for me with the intention of putting it into "Big Blue". I've got a nicely built TH400 to go behind it too.

I'm struggling with some ideas regarding engine computer management, and I figured that this would be the best place to pose my questions. The motor is actually set up for EFI - here's a quick video of the motor from the builder 454 .

So I was figuring originally that I might use the Holley sniper setup, but I believe that would require me to to upgrade all of the fuel system to play nice with the high pressure requirement of that system, which I don't really want to invest in. Plus the Holley system is sort of an a-la-carte thing and if I can avoid spending more on all of the different components, that would be ideal.

From there, I found the attractive and cheaper idea of running a stock TBI unit (with an adaptor plate so it'll play nice with the intake manifold) and a matching ECM for the 7.4, both of which would be ebay acquisitions. I do not believe that the stuff running the 350 would run the 454.

So here's where I have a few questions:

Since this is a built 454, would the OEM ECM be able to manage this without problems? If I had to guess, I'd guess "maybe".

What foreseeable issues am I going to encounter trying to run this motor with the OEM TBI setup? Would the ECM require tuning?

In the event that I'd keep the Holley EFI, would the OEM fuel lines be able to play nice with the added additional PSI from the increased demand? My guess here would be "probably not". For reference the existing system components are in great shape without signs of fatigue, etc.

Performance wise, am I insane trying to run this with the OEM gear instead of the sniper and an MSD 6AL, etc? I'm not necessarily trying to have the most beastly truck for drag racing. It's still going to be a truck that has to do truck things.

Thanks for your time, and your input/wisdom/suggestions. It's really appreciated.

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[df2x4]

@PlayingWithTBI is the resident TBI tuning expert, he can probably answer these questions in much more detail.

Short answer, yes, a factory 454 TBI system and PCM should be capable of running your new 454. It will most likely require some custom tuning though. I forget what the current go-to equipment list is for tuning a TBI PCM, but I know the Gearhead EFI forums are often referenced.

http://gearhead-efi.com/

Awesome truck by the way!

 

[PlayingWithTBI]

Short answer, yes, a factory 454 TBI system and PCM should be capable of running your new 454. It will most likely require some custom tuning though. I forget what the current go-to equipment list is for tuning a TBI PCM, but I know the Gearhead EFI forums are often referenced.

^^^This. Dave w (Old School EFI) there on GearHead-EFI can help you.

IIRC the 1228747 came with the 454SS and TH400 trans in 1990. For your application (BTW I can't open your 454 link) you'll need a bigger fuel pump and Adjustable Pressure Regulator to jack it up to maybe 18 PSI or more from ~13. Once you start tuning, you'll know by looking at your VE tables.

Another route to go is with the EBL Flash-II ECM

EBL_Flash

HTH

 

[Erik the Awful]

...the Holley system is sort of an a-la-carte thing and if I can avoid spending more on all of the different components, that would be ideal.

Bingo! If you can run the stock setup, do it.

If you do have to go Sniper, the only thing you need to do to your fuel system is upgrade to a Vortec fuel pump and put metric-to-AN adapters on your fuel lines so they tap right into the Holley. Don't forget that for GMs you have to pay $16 for that stupid 25 cent piece of steel to extend the throttle arm.

 

[MisterGrimm]

I'm not sure why you wouldn't be able to view the link, unless posting links from YouTube is forbidden - and if that's the case, I do apologize.

xc_hide_links_from_guests_guests_error_hide_media

I'll try once more:

 

[PlayingWithTBI]

I'm not sure why you wouldn't be able to view the link, unless posting links from YouTube is forbidden

Got it this time Sounds healthy too

 

[MisterGrimm]

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[Drunkcanuk]

Sweet!!!! How close to running is it? Looks like a stock TBI with a spacer, what did you decide to use to run this rig?

 

[MisterGrimm]

I'm still sorting out a few loose ends, but it is nearly ready to fire up. It is a stock TBI with a spacer. Good eye. I went with EBL Flash II for management. It seemed like the best choice for what I was trying to do.

 

[Drunkcanuk]

Nice. If I don't LS mine, and I hop up the 5.7, I'll probably do the EBL as well. Keep us posted on how that works for you. A few on here run it.