long runners or short runners bet is inveolved need answer

[DYNOED250]

Hey guys , i got a bet to seatle with my boss.
its about runner length and rev range.
he was tring to tell me that short runners r for down low and long runners r up high. i think its the other way around long runners for torque and short for up high applacations.

would short runner -top end
long runner -low end

i was talking bout efi so not sure if its different for carbs. i have an ed manifold on my crossflow and i posted a while back and we concluded that it was the runners killing up high, thats what gave me the idea.

Ps the bet was for 100 bucks please say im right

 

[MustangSix]

Generally speaking, Long runners are tuned for low end performance and maximize torque. Shorter runners are more effective at higher rpm and are optimized for top end hp.

 

[xctasy]

Far be it from me to suggest we all log on elseware to get answers, but the slant six forum had a good old heads up about this.

Check it out on http://www.slantsix.org/forum/viewtopic.php?t=7163

I do need to add something very important. There is an additional school of thought that says the wrong intake runner length, or too smaller venturi area for a carby engine, can be over come with limiting exhast port flow at higher lifts (~400 thou and above cfm exhast flow can be limited to less than 80% of the intake cfm). This promotes cylinder filling.

This allows a 500 cfm carb to deliver 350 hp with a very good single palne intake, when its practical limit is perhaps 175 to 220 hp on a street car. So the theory is very important, but can be circumvented by good cam design. The air speed at 221 hp is about 300 feet per second. At 350 hp it is a whooping 475 feet per second.

Check this example we thrashed last week.http://fordsix.com/forum/viewtopic.php?t=9303


I personally believe (based on info, not feelings) that when air speed exceeds 250 feet per second, the flow turns from a turbulant flow to super-critical, where standing waves, or eddies, form, sort of like what you see in the Murray River in flood. Vorticies form, and the level of resonance is proportional to the length and diameter of the fluid flowing. Changes in cross section and direction create standing waves too. It prevents the realatively free flow of the fluid (air in the case of an EFI system, not water or air/fuel) and creates an inability to have a proportional power increase, which is way some engines tend to heal over.

E.g. Non-GT40 5.0 efi intake manifolds don't allow more than 300 hp with the stock cam. GT40 Showa intakes heal over at 350 hp, which is why Ford Oz changed the upper intake on the 5.6 EFI. It's reported that all a GT40 intake can produce is 400 hp, and then resonace sets in.

 

[DYNOED250]

hehehe , sweet thanks for all ya help. more money for the corty


by the way did any one have trouble loggin in the last few days

 

[xctasy]

You bet we did. Me and addo, OO6, Fingers and the GM destroya are all on the member list, so we hung there for a few days.

Still faithfull Ford fanatics, but not one-eyed enough to hate Mopar's.

 

[Anonymous]

Hi guys,
I also had trouble loggin on in the last couple of days. I thought it was my crappy/slow computer.
Dont hate mopars, just gm products.
Noel

 

[Anonymous]

Hi guys,
Dont hate mopars, just gm products
Noel

same here mate, same here, my pet hate is hsv's!!!!!


hsv- i just dont want one.

mopars rock tho, they make feral power,

as they say, who cares what it is as long as its fast,


in my mind nothings as fast as a ford!!

FORDFORDFORDFORDFORDFORDFORDFORDFORDFORDFORDFORD
FORDFORDFORDFORDFORDFORDFORDFORDFORDFORDFORDFORD
FORDFORDFORDFORDFORDFORDFORDFORDFORDFORDFORDFORD
FORDFORDFORDFORDFORDFORDFORDFORDFORDFORDFORDFORD
FORDFORDFORDFORDFORDFORDFORDFORDFORDFORDFORDFORD
FORDFORDFORDFORDFORDFORDFORDFORDFORD ALL THEY WAY!!.

cheers.joe.

 

[DYNOED250]

gts = goes to slow
hsv - heapa shit vechical
hrt- hormone replacement theropy
holden- holes oil leaks dents engine nocks
holden- helping old ladys drive easier now
holden heaps of low down engine noises

 

[Anonymous]

holden- heavy old lumbering dinosaur excites neanderthals
holes, oil leaks, dents engine noises
hope out luck dosnt end now
hold on lads damn engines nackered

hsv- hype sells vehicles.


cheers.joe.