Injector Stack vs. SM Intake

That's not very big. Crower used 2.90" stacks on 427" BBC 40 years ago.

Individual runner injectors(AKA Hilborn and others) have advantages and disadvantages compared to a standard carb.

The IRs don't idle well and don't accelerate well off idle----they don't have an acceleration pump as carbs.

But if you are going to keep the RPMs above 4000, the throttle response is much better than a carb. A carb depends on engine vacuum to flow fuel---the IR flows fuel based on the mechanical metering block so fuel flow is instanteous, and the nozzles are very close to the valve. Throttle response is the reason sprint cars use them with great success.

In the past, IRs suffered compared to large plenium carb setups because of the smaller runner size---but this has been corrected with later IRs with runner size of over 3" in diameter. These large runner IRs allow RPMs as high as you are willing to run with good HP AND you can taylor each cylinder to max fuel/air mixture. You don't have to worry about rich/lean cylinders.

There is a learning curve with IRs---don't try to shortcut it!

The Indy 8-Stack is a 2.90" throttle bore, and Engler Machine and tool can make them much larger than that. A properly set up mechanical fuel injection unit will work at lower rpm's than 4000, and will also have a clean idle.

The IRs don't idle well and don't accelerate well off idle----they don't have an acceleration pump as carbs.

Backward.

So, by BS - you mean I'm right.

Maybe I am wrong----maybe you can get IRs to idle well-----or maybe our little pipsqueak engine is too small----we just don't concern ourselves with idle or lower RPMs----as long as it is smooth at staging and throughout the RPM range, we are happy.

Been wrong before, will be wrong before the end of the day!

Kinsler split shafts allow a good idle.
A even idle is really important so all plugs are heated the same before the run.

Mechanical stack injection is finickie to adjust.You have a high speed bypass and idle bypass to control excessive fuel,a main jet or pill controls the fuel feed,a slotted valve that increases the slot size is the throttle control.All the bypass and main feeds are controlled by pill size ,similar to jets.Many manufactures have modified these systems for better throttle characteristics.We just adjust for the best idle and maximum wide open throttle performance.We don't recommend mechanical stack injection for the street unless it is set up with a EFI system.

Ive seen guys do conversions where they have EFI injectors on the underside of the stacks , connect MAP to all of the stacks with small tubes on the outside to a miniature manifold and a TPS on one throttle shaft. Works really nice for the street.

Mechanical fuel injection is more race oriented than for the street. It is also easy to work on and tune, the problem is that most people start out learing how to tune carbs and then try to apply the same methods to fuel injection. I can make my little motor idle at 800 rpm in gear, and launch with a 1.20 short time. Of course it's much happier launching at 6200, but that's more the cam and heads than the injection.