CSFI to MPFI question.

[WallyV]

1997 CCLB 5.7 Nv4500 4x4

I don't post a bunch because the search feature works well.... I'm want to swap to a 383 (225k and a ton of oil consumption). When I replace the poppet style spider with a MPFI spider, what are the hp/torque limitations of the stock replacement (ACDelco 217-3029)?

I found a build with 400hp on a stock MPFI replacement 383 stroker, and other people saying anything over 350hp is a no go.

If an upgrade is needed what do you guys recommend?

Who has experience keeping their black box PCM and using black bear performance for a mail order tune with a 383 swap?

Is the Vmax intake spacer actually worth using?

Thanks in advance!

 

[Tachyon]

I can't speak to the aftermarket tune, I've been pondering that question myself. If money grew on trees, I'd buy my own HP Tuner kit and do it myself.

As for the 350HP limit some people are quoting, that would be on the original spider. Not the MPFI, which IMO is good for 400HP. My own 383 only has a Hypertech High Energy programmer tune, but still turns out close to 400. If you have a good fuel pump and pressure regulator/return, you should be able to get into that range.
Above that, most people will tell you that you need to make major fuel system upgrades. EG. Marine injection swap, aftermarket FI kit, etc.

I'm skeptical of intake spacers on the street, but make no claims to being an expert on this one so I'll defer to others.
I'd love to have a Corvette TPI type intake on one of these 383's though. I bet the long individual runners would really work great with this engine.

 

[kennythewelder]

1997 CCLB 5.7 Nv4500 4x4

I don't post a bunch because the search feature works well.... I'm want to swap to a 383 (225k and a ton of oil consumption). When I replace the poppet style spider with a MPFI spider, what are the hp/torque limitations of the stock replacement (ACDelco 217-3029)?

I found a build with 400hp on a stock MPFI replacement 383 stroker, and other people saying anything over 350hp is a no go.

If an upgrade is needed what do you guys recommend?

Who has experience keeping their black box PCM and using black bear performance for a mail order tune with a 383 swap?

Is the Vmax intake spacer actually worth using?

Thanks in advance!

I bought an intake spacer for my 97 5.7 L several years ago. It robbed power. It was a trans dapt brand I think. Its Its sitting in my desk drawer in my shed. On a Vortec, the only thing inside of the intake is air. There is no fuel in there, so increasing the volume of the intake by adding a spacer does nothing. As for the ribbed spinning air claimes, this is pure B S. It sounds like a good idea, but really does nothing but restrict flow. Done waste your money on a T B spacer. Not on a Vortec anyway.

 

[WallyV]

As for the 350HP limit some people are quoting, that would be on the original spider. Not the MPFI, which IMO is good for 400HP. My own 383 only has a Hypertech High Energy programmer tune, but still turns out close to 400. If you have a good fuel pump and pressure regulator/return, you should be able to get into that range.
Above that, most people will tell you that you need to make major fuel system upgrades. EG. Marine injection swap, aftermarket FI kit, etc.

These were my thoughts, but without firsthand experience I didn't want to speculate, and have to buy the same parts more than once.

I bought an intake spacer for my 97 5.7 L several years ago. It robbed power. It was a trans dapt brand I think. Its Its sitting in my desk drawer in my shed. On a Vortec, the only thing inside of the intake is air. There is no fuel in there, so increasing the volume of the intake by adding a spacer does nothing. As for the ribbed spinning air claims, this is pure B S. It sounds like a good idea, but really does nothing but restrict flow. Done waste your money on a T B spacer. Not on a Vortec anyway

The intake spacer I am referring to is this one.

I'm not into gimmicky air spinning devices, TB spacers or magnets on the fuel lines, but with the spider taking up space I can see how increasing the volume could help. Without any independent dyno charts and comparisons there is no real hard evidence either way.

Thanks for the responses.

 

[kennythewelder]

These were my thoughts, but without firsthand experience I didn't want to speculate, and have to buy the same parts more than once.



The intake spacer I am referring to is this one.

I'm not into gimmicky air spinning devices, TB spacers or magnets on the fuel lines, but with the spider taking up space I can see how increasing the volume could help. Without any independent dyno charts and comparisons there is no real hard evidence either way.

Thanks for the responses.

Oh my bad, but over $269 on a may be, IDK, but thats just me. For that kind of money, you could do a black bear tune. If you install one, let us know who it works.

 

[WallyV]

Oh my bad, but over $269 on a may be, IDK, but thats just me. For that kind of money, you could do a black bear tune. If you install one, let us know who it works.

No prob, just wanted to verify that we were talking about the same thing. There is a Black bear tune in the future for sure. I need to call BB and see what their experience has been.

 

[L31MaxExpress]

I bought an intake spacer for my 97 5.7 L several years ago. It robbed power. It was a trans dapt brand I think. Its Its sitting in my desk drawer in my shed. On a Vortec, the only thing inside of the intake is air. There is no fuel in there, so increasing the volume of the intake by adding a spacer does nothing. As for the ribbed spinning air claimes, this is pure B S. It sounds like a good idea, but really does nothing but restrict flow. Done waste your money on a T B spacer. Not on a Vortec anyway.

That would be a TB Spacer not the plenum spacer. The plenum spacer is a bit of a PITA to install correctly but has a very positive effect on these engines. All the spider junk in the plenum cuts down on the cylinders ability to breathe. With the spacer it opens up a better flow path for the incoming air. I had one on my Tahoe with the cammed 305. Made a very noticeable difference above 3,000 rpm. Not quite as noticeable of an improvement as an actual marine intake. I would not have bought the spacer new but paid $100 for it used from a wrecking yard (bought the whole intake with it installed and a newer MFI spider) and thought why not.

 

[Tachyon]

That would be a TB Spacer not the plenum spacer. The plenum spacer is a bit of a PITA to install correctly but has a very positive effect on these engines. All the spider junk in the plenum cuts down on the cylinders ability to breathe. With the spacer it opens up a better flow path for the incoming air. I had one on my Tahoe with the cammed 305. Made a very noticeable difference above 3,000 rpm. Not quite as noticeable of an improvement as an actual marine intake. I would not have bought the spacer new but paid $100 for it used from a wrecking yard (bought the whole intake with it installed and a newer MFI spider) and thought why not.

Yeah, I thought he was talking about the TB spacer, not the plenum spacer.
Nice to hear that the plenum spacers actually work. It makes sense given all the crap floating around in there messing up airflow.

 

[big_mike]

The pump is capable of supplying plenty of fuel, you can find MPFI units with higher flowing injectors than the AC Delco replacement unit. You won’t really know if your over commanding the capabilities of the Delco unit until you get into the tune. At that time you can get the tune to be driveable at least but will be leaving power on the table until you can buy the larger injector MPFI unit.

I have seen builds making 400 crank HP running a stock MPFI unit just fine.