440 mpfi manifold question

[Turkeyjerky]

Has anyone converted an edelbrock rpm manifold for MPFI? If so where did you dill the holes for the injectors? Did injector angle matter, I'd assume you'd want the injector pointed at the intake valve. Any help would be appreciated.

[Topcat]

This article would be a good guideline.

http://forums.holley.com/showthread.php?2547-My-MPFI-Intake-Manifold-Conversion

[Turkeyjerky]

Yea I've seen that, it seems to be only post I've found.

[Chryco Psycho]

I have used predrilled intakes but angling the injectors toward the head can only help

[go-fish]

It would be more economical to start with the EFI Victor rather than having one modified. The dual plane runners would be harder to modify vs. a single plane, too. Also, something I've been searching an answer to is when using port injection, is running a single plane intake better since the injectors are right at the intake valve squirting atomized fuel? Don't you want a big air moving intake for MPFI?
When using port injection you have a dry intake. Dual plane manifolds make more low end power in wet (carbureted/throttlebody) manifolds but aren't the virtues of a dual plane erased due to the location and sequential firing/ timing of the injectors?

[1 Wild R/T]

but aren't the virtues of a dual plane erased due to the location and sequential firing/ timing of the injectors?

Yes.... Fuel distribution at low speed is equally stabile unlike a wet manifold....  This would be my manifold of choice....

I just went to Edelbrock's website & they suggest the power curve is from 3500-7000rpms which matches the carbureted version of this manifold..... But that makes no sense, the fuel being injected on the back side of the valve means it should be perfectly suspended & the mixture should be ideal as well...  Just like EFI will mask a big cam it will also mask a high flow manifold....

[Chryco Psycho]

I will idle like a stock motor , I have done this with this exact manifold

[go-fish]

I just went to Edelbrock's website & they suggest the power curve is from 3500-7000rpms which matches the carbureted version of this manifold..... But that makes no sense, the fuel being injected on the back side of the valve means it should be perfectly suspended & the mixture should be ideal as well...  Just like EFI will mask a big cam it will also mask a high flow manifold....

I think Edelbrock uses flow numbers to come up with their intakes RPM ranges so the MPFI versions are going to have the same power curve as the Carbureted version. Looks the same on paper 

Saying EFI masking a big cam and masking a high flow manifold you mean that EFI changes the characteristics and performance of those parts? I don't see where it would change how a cam operates but port injection/ dry manifold definitely changes the process for how the manifold operates.

This is how I came to find the Victor EFI for small blocks. I am running a Super Victor Jr., which is a lot like the Victor EFI, but I was looking at going to a dual plane with my carb set up for better low end cruising but that meant a different cam too. Then I started thinking about port injection and keeping my Super Victor, however, i found out that buying an EFI ready intake is much much cheaper than  having one modified. Still leaning toward MPFI because of the sub-standard gasoline these days.

[1 Wild R/T]

I think Edelbrock uses flow numbers to come up with their intakes RPM ranges so the MPFI versions are going to have the same power curve as the Carbureted version. Looks the same on paper 

Saying EFI masking a big cam and masking a high flow manifold you mean that EFI changes the characteristics and performance of those parts? I don't see where it would change how a cam operates but port injection/ dry manifold definitely changes the process for how the manifold operates.

This is how I came to find the Victor EFI for small blocks. I am running a Super Victor Jr., which is a lot like the Victor EFI, but I was looking at going to a dual plane with my carb set up for better low end cruising but that meant a different cam too. Then I started thinking about port injection and keeping my Super Victor, however, i found out that buying an EFI ready intake is much much cheaper than  having one modified. Still leaning toward MPFI because of the sub-standard gasoline these days.

The reason a big cam is choppy is the poor fuel distribution at low rpm's, EFI fixes that, even throttle body EFI helps but port injection makes a big nasty cam seem pretty tame....  Do you get the low rpm torque of an RV cam? No.. But it's allot better than your typical 260-270 @.050 cammed carberated engine...  Intake manifold is the same deal, because the A/F mixture in the cylinder stays very close to ideal you get to keep allot more low rpm torque & throttle response....

[go-fish]

Gotcha on the  cam. Basically, what you're saying is that the more ideal conditions for fuel atomization the cam will perform more representative to how it should on paper. So, if going with MPFI you can go a little more radical on the cam?

[1 Wild R/T]

Your better at explaining it but Yup...

[go-fish]

Your better at explaining it but Yup...

You know what? I don't even know if I get it yet 

[1 Wild R/T]

Lets try it this way.....  You know with a carb fuel is drawn through various passages by air flowing through the barrels of the carb.... Greater airflow creates a stronger draw & more fuel flows... If you allow to much airflow to quickly the fuel flow will stop because the airflow stalls & the vacuum signal falls.....

Kind of like sea spray on a windy day.... The wind dies down there is no sea spray...

Bigger cams & bigger manifolds are more prone to airflow stalling at low RPMs because you have a reduced vacuum signal, which is the signal the the carb sees.....

With fuel injection fuel flow is a function of high pressure spray.....

Guy with a garden hose, yeah he can spray further on a windy day, but if the wind dies down he can still get you wet.....


Theres lots more to it but thats the readers digest condensed version....

[Chryco Psycho]

the other problem is fuel is never completely atomized / evaporated into the air flow with a carb , the injector does a far better job so with the fuel mixed at the carb it has a long way to travel & often liquid fuel will fall out of the air flow making the mixture too lean to burn