L31 to MPFI with other than Marine Intake Manifold

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Mange16v

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I am going to be getting into my 99 Tahoe at the end of the summer and I have been looking into going to an aftermarket intake manifold that preferably isn't the cast marine version. I am going to do a bit of headwork, intake manifold and a cam. I want to keep Air conditioning and Cruise control and I will use Bosch EV14 Injectors.

These are a few manifolds I was looking at but some look like they might not be compatible with AC and Cruise because of the throttle body.

https://www.holley.com/products/intakes/efi_manifolds/parts/9901-107

https://www.summitracing.com/parts/edl-29145/questionsanswers/

https://www.edelbrock.com/pro-flo-xt-vortec-sbc-intake-manifold-7138.html

I pulled this from another site;

"You would need injector connectors, that you solder into the big black Vortec connector wiring. Most are just cutting that connector off. Crimp, Solder, Seal.

Attach a throttlebody and air intake.
Drop in Vortec distributer and mount coil, or use EFIConnections CNP(coil near plug) setup and 8 LS1 style coil.

PCM tune to disable EGR, and its OBD2 SES light, tuning for the IFR(injector flow rating)

Attach fuel supply and return lines.

Attach PCV line to vacuum somewhere.

Attach Evaporative Emissions lines to vacuum, or disable Evap function and OBD2 SES light

Hook up cooling system"

So a couple of questions I can't find specifics on... First what is a good company that can tune the factory computer for the injectors and remove the EGR/EVAP function? Can I use all the other factory Vortec components (distributor to be exact). Has anyone used the Edelbrock Pro Flo with Air conditioning? What else might I want to think about with wanting to stay as close to factory with losing the poppet valves, getting more torque and keeping drivability?
 

iamdub

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Best I can offer: Back in my boosted S10 days, the Edelbrock 2114 manifold was the answer to achieving MPFI with standard injectors to have fueling for boost and nitrous. Your '99 5.7 would be the same except with four extra wire connections for the two additional injectors. The Holley 9901-107 in your first link looks very similar to the Edelbrock 2114 I referred to. Maybe Edelbrock has a 5.7 version of the 2114 to compare? The idea was to use the Edelbrock manifold with an adapter to convert the 4-bolt carburetor mount to the 3-bolt throttle body pattern. Edlebrock had compatible fuel rails and crossover hoses that bolted on. I believe the original distributor and all was reused. I don't recall what was done about the EGR system. Either it was retained as well or capped off. If your '99 has the 411 PCM ("silver box" and not the "black box"), then it can be tuned by anyone that tunes '98+ LS engines. You could have them delete the EGR and maybe EVAP from the programming. I don't see what effect any of this would have on the A/C operation. The result, other than fuel capacity for boost, is much more precise fuel tuning (better MPG), more reliability, better drivablity and, I think, a noticeable bump in power.
 
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Mange16v

Mange16v

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Thanks for the response. As for the AC I see the Pro flow XT might interfere with the mounts for the compressor but that's all. And I guess with some maneuvering you can make it work. I actually just received a response back from Edelbrock and they said neither would work. BUT... I am assuming that's because I intend to put it on a vehicle with EGR and other emissions controls.
 

iamdub

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Thanks for the response. As for the AC I see the Pro flow XT might interfere with the mounts for the compressor but that's all. And I guess with some maneuvering you can make it work. I actually just received a response back from Edelbrock and they said neither would work. BUT... I am assuming that's because I intend to put it on a vehicle with EGR and other emissions controls.

Yeah, they gotta cover their butts and be PC with their replies. I wouldn't bother with the Pro-Flo and the Victor is for a high-RPM race engine.
 
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Mange16v

Mange16v

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Unless I can find something that operates well in the lower RPM range it looks like I will be giving the ebay cast Marine intake a go. Not much out there for the Vortec engines. But I don't want to get into a LS swap in something like this.
 

zraffz

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I know I am a few months late to reply but I have been working on an L31/350 Vortec MPFI intake manifold. I am still early in the testing stage.

This is a dual plane intake manifold with an estimated RPM range of 1,000-6,000 RPMs (I could change the base manifold to be a 1,500-6,500 RPM manifold in the future). It is complete with fuel rails, injectors, injector harness, adjustable regulator and accepts a factory 3 bolt Vortec style throttle body.

Would this actually have a market to sell? I could probably ship them anywhere in the USA for around $750 (I could put a base tune in your PCM for $50). I have yet to address a few issues; such as the EGR or retaining the factory air intake system but I am slowly working on it!
 

Grumpa

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I know I am a few months late to reply but I have been working on an L31/350 Vortec MPFI intake manifold. I am still early in the testing stage.

This is a dual plane intake manifold with an estimated RPM range of 1,000-6,000 RPMs (I could change the base manifold to be a 1,500-6,500 RPM manifold in the future). It is complete with fuel rails, injectors, injector harness, adjustable regulator and accepts a factory 3 bolt Vortec style throttle body.

Would this actually have a market to sell? I could probably ship them anywhere in the USA for around $750 (I could put a base tune in your PCM for $50). I have yet to address a few issues; such as the EGR or retaining the factory air intake system but I am slowly working on it!

Did you make any headway on the "Kit" you mentioned assembling? I would think there would absolutely be a market.
 

TahoePotato

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Hello Everybody - I'm with my '98 Tahoe in Baja California absent any decent tune shops and tools. I would love to order a Marine Intake Manifold prebuilt for 'bolt on' to get some better mileage power. If anyone wants to be a wrench-for-hire I'd love to work something out.

Thanks!
 

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