Speedmaster 8 Stack

[Saltshaker]

Anyone using this system? Is the gas mileage better then running Webers?
Jon

[cammerfe]

I've used Webers on two different engines. On one, I switched from mechanical injection to the Webers and found that the Webers were almost as good, MPG-wise, as the injection, DEPENDING ON HOW I DROVE IT. In the other case I Weberized from another carb set-up, and after a bit of tinkering, got an improvement.

On the other hand, the sophistication of today's EFI probably gives the benefit to the electronic system. But, in my case, I've not tried stack injection. The manifolds very likely have balance passages,  but the lack of any meaningful plenum must be some sort of a handicap for street driving. Good Luck if you go that route.

KS

[cleandan]

I have used a very early version of the electronic 8 stack injection system on a 427.
You will need a few specialized tools to tune each stack.
Be certain you have the ability to individually adjust each butterfly to its own best position.

The early system I was using was shaft mated in pairs, which meant I had to literally bend the butterfly shaft in order to adjust each individual intake stack...and this did not work so well.

Because each stack is directly feeding into a single cylinder, with no plenum to equalize the intake charge and impulses, thigs get touchy.
As your tune closer and closer to correct you will find a balancing act the seems to be on either side of "good" while never really being able to find "just right".

Keep in mind, my system was and older version...actually one of the first versions from the 1990's, so I am certain improvements have been incorporated.

The system I tuned ran very well, great by most peoples standards, but was never quite "right" with little pops and skips every once in a while.

The throttle response was very crisp and predictable, but because the intake I was using was biased toward race engines it never was awesome with around town, slow speed, slight throttle conditions. It worked well enough but it also had some characteristics you just needed to get used to.

The whole tuning process was pretty involved too, with a set of steps that must be followed in order to arrive at a good end result...at least that is what I was told to do.
I was even in direct contact with the developer of the system for a period as I tried to get things dialed in just right.
We followed ALL the rules to the letter and then he finally admitted this particular system never did work perfectly, specifically because of the lack of individual butterfly adjustability.

After that I scrapped the "rule book" and tuned for best driving characteristics while reading plugs, listening to the engine, taking temp measurements at the header flange, looking at exhaust residue and any other tells I could muster to help me get there.

After a few days of fiddling around it was pretty good all around, but never got perfect.

I honestly think if you can make all the air/fuel adjustments at each stack, along with very fine, controlled individual butterfly adjustments so a tune per cylinder is capable, the system should work very nicely.