IR Manifold and Port size

[jacksoni]

I was listening to the Jere Stahl interview and he mentioned that port sizes/cofiguration might be different with an IR manifold (ie Hilborn like injection or Weber like carbs). The topic was changed before he expanded on that. Does anybody have thoughts about this? Most of the stuff I have read here is related to carbs and normal manifolds/tunnel rams etc. What differences in the head/valves/tuning with IR manifolds? Assuming you can get the tuning (mixture) right does anyone have a preference? That is- all other things equal, will an IR manifold tuned properly, make as much or more power as, for instance, a good tunnel ram and carbs, tuned properly? I don't know the rules- if a Pro Stocker could run injection, would they? Asked another way, if no rules, what would you run?

[Walline]

I am no expert on the subject, but I would think one benefit would be better tuning ability(per cylinder) no cylinder distribution problem from sharing intake with other cylinders. Also I would think better low end and midrange, less reversion(from other cylinders) Could then use more camshaft.(duration) Just a few thoughts.

[dvkk]

Also I would think better low end and midrange, less reversion(from other cylinders) Could then use more camshaft.(duration) Just a few thoughts.

This is correct. All you have to do is look at what the air cooled VW guys are doing. On those engines the 2 sets of intake ports are over 2' apart so a common plenum manifold in the center doesn't work very well.
The local V8 guys don't believe me when I tell them the cam duration I run. In my daily driver, my cam has a duration of 256º @.050" and with IR intake manifolds and carbs it drives like a modern FI car. I used to run a cam with 262º, and a friend of mine uses a 274º @050" cam for his summer cruiser.
With IR manifolds you can also run apparantly massive carbs and still have great driveability. My friend's engine is 142 ci, and he has 4bbls of Weber carbs, each with 2.0" throttle plates. In comparisons, his carbs will flow more than an 1100 Holley Dominator.

[Guest]

In contrast to what you see in VW engines, 410 sprint car engines have short duration cams and individual runners. Although duration is in the 260's, a good 410 sprint motor will make very good power to 8000 rpm. They are running them over 8000 on the racetrack.

Perhaps the VW must run such long duration due to an inefficient induction system. Are the individual runners very small or very long?