Fuel Injectors In A 99 5.7

distaff · February 20, 2010

I have a 99 Suburban with a 5.7 GM Target Master (stock rebuilt crate motor from GM) installed by the previous owner 25k miles ago. I am thinking about turning it into a bit of a sleeper, and looks like I can get a 383 stroker kit for under $800. I will look at doing new heads or porting and reconditioning the stock ones and putting in a cam (could use some advice on these point as well). I'll also re-program the computer. I don't think I need to worry about the bottom end as it is not going to see real hard duty.

My question is about the injectors. I have some issues with them, one seems to leak. I can replace them with stock, or I can get them cleaned, but I am reading that they are not great, and I don't seem to be able to find any obvious upgrades.

Any suggestions?

distaff · February 21, 2010

I am new to GM engines, I have a 69 Ford F100 4WD I restored and put a very nice 410 in it. I had understood that one of the advantages the GMs (especially the small blocks) had was that many more performance options were available than were avalailable for the Fords (especially the old FEs).

Kind of surprised at the lack of responses. I assume that this means that there really is no way to improve the poor fuel injection system on these L31s. I have found other discussions about using a marine intake that provides a true multiport injection without the stupid spider system.

Perhaps this is not the right forum - if I asked a question like this on the Ford-trucks forum I'd expect at least 10 posts in the first 24 hours. Is there a forum that is more focused on performance upgrades?

thearborbarber · February 21, 2010

Do away with that goofy cpi system. You will be chasing your tail. Using the marine intake to convert to sequential is the way to go.

Also you don't get get your panties in a bunch if your post isn't answered as fast as your like. Some folks may only read the board once a week. Besides the ford people have lots of time to read boards like this because their trucks are in the shop.

Anyway, I have found alot of useful L31 info on this forum;

http://www.pacificp.com/forum/viewforum.php?f=1

If you dig around you will find a lot of guys that have done big HP build ups.

distaff · February 21, 2010

Thanks for the reply. That is the only solution I could find on the net. Only problem is that I can't find anyone who seems to sell the marine intake.

thearborbarber · February 21, 2010

These folks seem to have a good rep.

http://www.cfm-tech.com/chevy-vortec.htm

MaForrest · February 24, 2010

I am going to have a 383 built for my '97 here in awhile and have heard alot about people useing the marine multipoint rail system over the spider type. ( I dont know the proper names, sorry) Whats the main benefits for useing the marine intake? Will the truck remail smog legal?

Badass69 · March 20, 2010

http://www.napaonline.com/Search/Detail.as...9+50014+2014085

This is a simpler upgrade for more milder builds for the Vortecs. I have this unit for my 96. It is a complete conversion that dumps the stock poppet valve CPI setup for a true multiport with 8 injectors. If you are going to be around the 400 HP maybe a bit more at the max, this will work just fine. I am adding the Vmax intake spacer ( lifts the entire plastic upper plenum an inch, not to be confused with a throttle body spacer) to gain some plenum volume and a bit of rpm. The problem with the stock Vortec intake is the injector assembly is inside your air plenum and it restricts flow. The spacer will help it breathe in the higher rpm if need be. I could do the marine intake and it does work well but for most people so does this. I am adding an XR 264 Comp cam, 1.52 roller rockers,long tubes, exhaust, the above injection upgrades, a custom tune and some transmission upgrades to my now completely stock 29000 original mile 96. Its a 2 wheel drive extended cab short box with 373 gears so with a mild stall ( 2600 or so ) this should do quite nicely.

rodram · March 21, 2010

.. look for the MFI conversion kit for these 5.7L Vortec ... gmpartsdirect has them listed online and they are available through dealers and other parts suppliers..

.. the MFI is not necessarily a performance upgrade ... but it is the stock fuel injection system for the big block engines (7.4L) of the day ...

.. the Multiport Fuel Injector (MFI) takes away the potential issue of sticky deposit buildup on the poppet valves on the SCPI stock systems on the 4.3:, 5L, and 5.7L Vortecs

Badass69 · March 21, 2010

.. look for the MFI conversion kit for these 5.7L Vortec ... gmpartsdirect has them listed online and they are available through dealers and other parts suppliers..

.. the MFI is not necessarily a performance upgrade ... but it is the stock fuel injection system for the big block engines (7.4L) of the day ...

.. the Multiport Fuel Injector (MFI) takes away the potential issue of sticky deposit buildup on the poppet valves on the SCPI stock systems on the 4.3:, 5L, and 5.7L Vortecs

Okay there is some confusion here so let's clear it up. The MPFI setup that GM has for the small block and V6 Vortecs shares absolutely nothing with the 454. The 454 had an external fuel rail with conventional injectors plumbed into it. Not the internal MPFI setup like how the small blocks are setup ( after you do the conversion).

The system I pictured is the identical setup that any dealer would sell you. The units are all made by Delphi no matter who sells them. The dealership is a ripoff no matter how you look at it. I picked mine up, new in the box off of an Ebay store for half of what the dealer wanted for it.

And no it was not a performance upgrade, but a driveability one. GM released it as a TSB to combat the clogging issues with the CPI. The injectors on it are 19 lbs per hour but that is rated at around 44 psi. Vortec small blocks use closer to 55-60 psi to run so they actually flow around 24 pph. As I said, good enoug for a 400 Hp or so build........

rodram · March 21, 2010

.. look for the MFI conversion kit for these 5.7L Vortec ... gmpartsdirect has them listed online and they are available through dealers and other parts suppliers..

.. the MFI is not necessarily a performance upgrade ... but it is the stock fuel injection system for the big block engines (7.4L) of the day ...

.. the Multiport Fuel Injector (MFI) takes away the potential issue of sticky deposit buildup on the poppet valves on the SCPI stock systems on the 4.3:, 5L, and 5.7L Vortecs

Okay there is some confusion here so let's clear it up. The MPFI setup that GM has for the small block and V6 Vortecs shares absolutely nothing with the 454. The 454 had an external fuel rail with conventional injectors plumbed into it. Not the internal MPFI setup like how the small blocks are setup ( after you do the conversion).

The system I pictured is the identical setup that any dealer would sell you. The units are all made by Delphi no matter who sells them. The dealership is a ripoff no matter how you look at it. I picked mine up, new in the box off of an Ebay store for half of what the dealer wanted for it.

And no it was not a performance upgrade, but a driveability one. GM released it as a TSB to combat the clogging issues with the CPI. The injectors on it are 19 lbs per hour but that is rated at around 44 psi. Vortec small blocks use closer to 55-60 psi to run so they actually flow around 24 pph. As I said, good enoug for a 400 Hp or so build........

Hey.... who pissed in your cereal..?

All I was trying to do was tell the OP that there is something out there on the market available from dealers and from other parts houses called a MFI Conversion Kit that will take away the problem of the OE Vortec small block injectors...

Badass69 · March 21, 2010

.. look for the MFI conversion kit for these 5.7L Vortec ... gmpartsdirect has them listed online and they are available through dealers and other parts suppliers..

.. the MFI is not necessarily a performance upgrade ... but it is the stock fuel injection system for the big block engines (7.4L) of the day ...

.. the Multiport Fuel Injector (MFI) takes away the potential issue of sticky deposit buildup on the poppet valves on the SCPI stock systems on the 4.3:, 5L, and 5.7L Vortecs

Okay there is some confusion here so let's clear it up. The MPFI setup that GM has for the small block and V6 Vortecs shares absolutely nothing with the 454. The 454 had an external fuel rail with conventional injectors plumbed into it. Not the internal MPFI setup like how the small blocks are setup ( after you do the conversion).

The system I pictured is the identical setup that any dealer would sell you. The units are all made by Delphi no matter who sells them. The dealership is a ripoff no matter how you look at it. I picked mine up, new in the box off of an Ebay store for half of what the dealer wanted for it.

And no it was not a performance upgrade, but a driveability one. GM released it as a TSB to combat the clogging issues with the CPI. The injectors on it are 19 lbs per hour but that is rated at around 44 psi. Vortec small blocks use closer to 55-60 psi to run so they actually flow around 24 pph. As I said, good enoug for a 400 Hp or so build........

Hey.... who pissed in your cereal..?

All I was trying to do was tell the OP that there is something out there on the market available from dealers and from other parts houses called a MFI Conversion Kit that will take away the problem of the OE Vortec small block injectors...

Well so did I if you had actually read my post. But I don't get how I am being pissy. I just corrected you in saying it's like the Vortec 454's system because it is not. And then proceeded to explain my own post somewhat further. I don't see how or why you are taking it as something negative towards yourself, it's an open forum, just let it go.

And really, why are people on this forum so damn defensive and fanboyish? If you post anything that is not in agreement with about 1/2 a dozen high post count members you get torn apart...... or banned. Yikes, what a friendly happy place this is. Don't ever mention paint issues, oil consumption with AFM, or really any problems with any late model GM truck or be banished or belittled by a bunch of juveniles. Yeesh. No Rod, that really has nothing to do with you btw.... just sparked something is all.

nubuilder · March 25, 2010

Sorry to jump on the wagon so late, but on the pacificp.com forum about the swap to the marine intake, someone posted a link to Michigan Motorz that had the brand new intake for sale for $800. Recently, they no longer have it.

Does anyone know of another site that sells them new? What about used?

Whenever I do rebuild, I'd love to build a 383 stroker using the marine vortec intake and the throttle body from cfm-tech.com.