5.7 Vortec SCPI to MFI Manifold Swap

[1998_Silverado_WI]

In the new issue of Hot Rod magazine is a tech question asked about upgrading the cam in a '96 Chevy truck with the Vortec engine, along with questions about ECU tweaks and info on the restriction of using the stock intake manifold. This led me to wondering what it would take to end up with the induction setup that I would like installed on my '98 Silverado, especially since the local Chevy dealer wants to charge me between $800 and $1,000 to remove the intake just to replace the leaking intake manifold gasket that only leaks a drop here or there, and not even enough to leak onto the ground when parked...

I have seen the posts for converting from SCPI to MFI using OEM parts from the GM parts department, but I would like to know if anyone knows of an aftermarket MFI swap that could be done on the Vortec engine to get away from the stock 2 piece intake, yet will work with the factory ECU? I am looking for any information on what would be required such as wiring harness changes or wiring harness adapters that will allow for an easy plug and go setup, and if the stock ECM will not work as is or if an aftermarket fuel management unit like a BigStuff 3 alone or piggybacked with the ECU could/should be used. Are MFI kits like the manifold, injectors, and throttle body available from Edelbrock or Holley compatible with the stock ECU to start with, and then upgrade to a BigStuff3 in the future to allow for tuning to accommodate upgrades and modifications to the engine? Eventually I would like to be able to upgrade to a little more aggressive cam, swap in headers and true dual exhaust (I live in the country, no smog inspection/testing required here) and finally add a supercharger or turbo. I don't see the stock Vortec intake working for these changes as the injectors alone aren't upgradeable to larger units to handle higher power levels, along with airflow restriction that limit power potential.

I am looking to retain the Vortec engine (I believe it is a very good strong base in which to build upon) so I can piece together my final package as I go and with what I can scrape together over time while on the very limited budget I have as I am disabled and receiving disability. Ideally I would love to swap an LS1/3/6 into my truck, but that's far too big of a cash outlay way too much work for me to do all at once in order to get my one and only ride rolling again. I also want to retain full use of all the electronics that came on my truck, even the generic "security" setup and factory radio, ABS and air bags, etc. that will also allow all my dash instruments to work without having the check engine light lit up constantly.

Thanks in advance for any help you can provide!

[j cAT]

If I had a limited income and had to have this work done by a shop a vehicle this old would not make any sense to me.

I would not spend an extra buck on a 1998 vehicle to modify it with limited funds..

[1998_Silverado_WI]

The work won't be done in a shop, I will do it myself. I can do a limited amount at a time by myself, and that's why I plan on doing upgrades one at a time even on a limited budget. If I didn't have a limited budget, I could just farm out the work along with getting the best parts available, and I wouldn't be posting on here... right? I could also upgrade the 383 I built for the '68 Impala I had 10 years ago to make it compatible with my factory electronics in the truck for an easy 150+ HP upgrade from the factory Vortec, but that's a whole other post.

It might be a '98, but it's a New Mexico truck in immaculate condition, absolutely no rust, every factory option available, Line-X bedliner, upgraded head & tail lights, heavy duty chromed grill and brush guards (Bambi protection), tuned engine with aftermarket air filter/intake kit, drilled and slotted brake rotors with ceramic pads, aftermarket speakers/amps/sub, aftermarket remote start, keyless entry/alarm, etc. Since the truck is in such great condition and I can do the work myself, I plan on keeping it for a very long time. One thing to keep in mind is that even though someone has an older vehicle and it might not seem worth the effort to you, it's what they want and are happy with.

[j cAT]

Originally Posted by 1998_Silverado_WI

Since the truck is in such great condition and I can do the work myself, I plan on keeping it for a very long time. One thing to keep in mind is that even though someone has an older vehicle and it might not seem worth the effort to you, it's what they want and are happy with.

why did you go to the dealership for a simple intake job ? you can do this yourself !

I keep vehicles a long time. working on #4 now since 1967...

my last vehicle before the new 2000 silverado had 380,ooomi..original engine and transmission no repairs...sold it after 17 yrs..

my 2000 silverado I was going to modify to use CNG..this costs about 6-7,ooo.oo..since it is going on 12 yrs old this would not make sense to me ....my next new vehicle I plan on buying or converting to CNG.

If you are in wisc that new mexico vehicle will rust out in no time !

[1998_Silverado_WI]

I didn't take it to the dealer to replace the intake gasket, it was in for an oil change and they went over the truck with a fine-toothed comb. I bought the truck from a dealer for a screaming deal that included a 3 year parts and labor warranty on the drivetrain. To keep the warranty active I had to take it into a shop for the oil changes so it was entered in the computer, and I don't trust quick lube shops because they let any idiot that can hold a wrench change oil. I got a CarFax report when I bought the truck, and I'm the second owner. Anyway, the service dept. at the Chevy dealer told me that a couple drops of coolant were found, so they wanted to replace the gasket. I've never seen a drop anywhere under the hood or on the ground, so I think it's BS. Even had a mechanic buddy climb into the engine compartment (literally) and couldn't find anything leaking. The only other thing they could find at the dealer was the serpentine belt needed to be replaced immediately, yet when I got home it only looked a little worn without any cracks and had good tension. The only thing I've had to do for repairs since buying it was have the pressure hose on the power steering replaced. The tech that did the job quoted me 1 1/2 hours, but was done within a half hour. I asked why there was such a different in the times and he said "We normally quote a longer time because the hoses are generally rusted on and we have to fight with them, but it was so clean under there that the hose came right off. I wish they all were like that!".

Yes, rust is a huge problem here in the north, but I be sure to get a super wash with the underbody flush once a week during winter, then in late spring I park the truck over a lawn sprinkler with the pressure cranked up for a few hours, moving the truck around here and there to get full coverage to help work away anything that could be left over from winter. Then I take a stiff bristle brush and be sure to clean off as much of the body and underpinnings that I can. These steps really pay off. If she'll last at least another 10 years I'll be happy!

[j cAT]

you must not be from the rust belt . even a new vehicle with the best of care operating in this environment will rust out in a few years..

brake lines are a big problem. the rocker panels also.

road chemicals attack the finish and chrome / wheel parts..

10 years is very hard to do unless you do not drive this in the snow or when the roads are wet with de icing chemicals..

I do my own oil changes..this includes drive train fluids. I use the high quality oil filters and synthetic lubes. I don't trust any lube jocky..

I have been given free oil change coupons from the dealership many times , NO WAY !

with any leak the level will drop. with your 98 you should have dexcool in it... this would require replacing every 3-4 yrs and then mixing with distilled water. I use a 65% dexcool mix to 35 distilled water..I used the distilled water even with the silicates coolant in the 1983 vehicle ..never any leaks ...

If you have a intake manifold leak it will not take long to show..once the metal corrodes the gasket will push out...

[j cAT]

you must not be from the rust belt . even a new vehicle with the best of care operating in this environment will rust out in a few years..

brake lines are a big problem. the rocker panels also.

road chemicals attack the finish and chrome / wheel parts..

10 years is very hard to do unless you do not drive this in the snow or when the roads are wet with de icing chemicals..

I do my own oil changes..this includes drive train fluids. I use the high quality oil filters and synthetic lubes. I don't trust any lube jocky..

I have been given free oil change coupons from the dealership many times , NO WAY !

with any leak the level will drop. with your 98 you should have dexcool in it... this would require replacing every 3-4 yrs and then mixing with distilled water. I use a 65% dexcool mix to 35 distilled water..I used the distilled water even with the silicates coolant in the 1983 vehicle ..never any leaks ...

If you have a intake manifold leak it will not take long to show..once the metal corrodes the gasket will push out...