intake runner length

[wideopen231]

Ok lets open a  gallon bucket of worms,screw the small cans.

On my injected hemi using BAE billet heads.My first design intake has a 8.5"  valve to top of runner.I have a second thats almost done(tons of welding on one of these) is is my shorty(better veiw too) 6" from valve to top of runner.Both have same top opening,so shorty has stronger taper.By theory shorty should have more top end,longer intake should have broader power band and more towards bottom.Note the current Jr. fuel cars running stubby injector and no tubes while spinning the crap out of them.

  while only real world track time will tell which works better. Wondering what thoughts some here might have on which would be better  to  try first while getting base line on  car.  I am leaning toward longer runners right now.  My thinking is broader tunning window easier to get into working ball park. Next question is how much will change effect car.All opions right now no wrong or right.  Well unless you have experiance with being overthinking nut case that loves tunning for power.

[masracingtd1167]

I have never played with runner length but I can tell you that plenum size can change performance . I have seen guy's who put spacers under there injector hat and slow up . I made my plenum a little smaller and picked up a little about .04 not big but some . The trend in Comp right now is short runners and a big plenum but that is on gasoline .

[wideopen231]

Hey Bill .04 for something that minor is big IMO.Any idea how much area was changed ,percentage wise?I have pretty much minimum plenium,but I do have adapter box on top.Eliminating it would cut open area down a bunch and I have thought about it.Problem is distance from #1 to #8 port is quite a bit more than opening in present injector.I do have a custom piece on shelf that is lower and has longer body.
 If you don't mind where did you pick up et.Early like 60' mostly .topend or over entire track?
             
  Thanks for info

[wideopen231]

 been playing around on wallace calculators. Changing nothing but upper rpm from 9000 to 9750 resulted in design length of 9.33 to 8.65 almost 3/4' shorter,dropping to 8500 it stretched intake length to 9.8. Ratio wise it is about .1 per hundred rpm.Well with my setup anyway.

  On plenum there is a note about some guy named Grummpy stating that plenium volume can screw you up quick.
  Learned something new to day so at least I did not waste the day.Now if I can fit 300 days into one.LOL

  Going to research plenium volume little more. Thinking using hat injector means hat area has to be included in total area.Wondering about totalarea of imtake track(port and runner) vs cylinder area.  49.5 ci(cyl)vs 40.38 runner at present . Maybe i'm not far off as is.Yea that will happen.