Intake designs

[Chryco Psycho]

intakes
Lets take a look at intake manifolds
there are various designs & reasons for the designs to be used
as with cams this is one area where often the wrong intake is used for an application
there are 3 basic designs of intakes ,
- dual plane intakes
- single plane intakes
- tunnel ram intakes
Intakes are made from Cast Iron or Aluminum , the factory has used both , the aftermarket
uses alum virtually exclusively

Any intake used Must be matched to the Cam so both work at the same RPM , having a cam that works at
very high rpm matched with an intake that works at low rpm will give extremely disappointing results
by the time the cam starts to work the intake is restrictive , it is the same problem if you reverse
the situation  witha cam that works at low rpm & an intake that works at high rpm the 2 will not make
power at the same time & the results will be disappointing

The Dual plane is designed to get good throttle response at low rpm divides the carb in 1/2 so 1/2 of the
engines cylinders use 1 side of the carb . Thuis is done to reduce the amount of air that needs to be
moved when the cylinder starts to pull the air in so with 1/2 the volume of air to move it is easier
to get it moving & helps to more completely fill the cylinder at low RPM , this also increases
signal at the carb & allows the carb to react more quickly giving better response fuel
atomization which can also increase gas milage , the down side is at hiher rpm the carb seems
smaller& will limit high rpm power , aslo the entracne into the heads is different for the
upper & lower plane so flow into the heads is not as even. To make power at higher rpm with a
dual plane  you must increase the common plenum area under the carb & use a bigger carb
to get enough flow , the 6 pack is awesome at this , the plenum is large as it goes under
all 3 carbs & you have 1/2 of approx 900 cfm for only 4 cylinders to draw from , in tests
the   6 pack has proven to be as good a most of the best single plane intakes & carb
combos aavailble today , it big drawback is the cost at more than 2x the cost of the best
single 4 bbl carb & intake packages available
The Best dual plane intake is the Performer RPM but hood clearance can be an issue the ther
decent intake is the old CH4B 

the single plane is the most versatile intake. by changing the runner shape & size & more
importantly the plenum volume a single plane can be made to work at virtually any rpm
By making the runner smaller & decreasing the volume of the plenum a single plane can make
power in the same low rpm range as the dual plane & usually with a smaller carb as well
which again will increase signal at the carb , the advantage is at higher rpm any single
cyl can draw from all the venturis in th ecarb instead of just 1/2 meaning you can have
the same responsiveness @ low rpm without the choking effect at higher rpm . conversely
as plenum size is increased & the runner volume is increased signal is lost at the carb ,
more air volume has to moved to fill the cyl & low rpm response is lost but at higher
Rpm breathing is dramatically improved as the time to fill the cylinder is shortened
so the more air close to the valve the bette. To illustrate this better at ilde the
intake valve opens around 6 x / second , whereas at 7200 rpm [yes this is possible I
shifted my 440  Duster there for 9 Years] the valve opens 60 x / second!!
The best intakes make the turn early into the head & have a straight run at the port
into the cyl head this helps to equalize distribution into each cylinder, Like the M1
Holley Street Dom & Victor , poorer intakes are the Torker series & Team G which make
a sharp turn right at the head which causes a lot of turbulence & the cylinder filling
is uneven
For good results at lower RPM the Street Dom is best & the torker [original not torker 2]
work well The Street Dom also is good for higher RPM & averages the best power over all rpm
range , for Higher RPM the M1` & Victor are the best Large single planes

  The tunnel ram comes in many forms , the whole  purpose is tuning the pulse waves inside
intake , as the intake valve closes it sends the shock wave back into the intake & will
bounce back towards the valve , ideally this shock wave / pulse needs to arrive back at the
valve as the valve opens again to provide a passive supercharging effect at high rpm ,
The first use was the long rams in the early 60s 413s at approx 26" long & tuned to work at
approx 3200 rpm for peak power at 70 MPH for cruising a passing on the highway , the shorter
the intake runner the higher the rpm the effect works at , the Slant 6 had the Hyper pack
intake with a 4bbl carb which is a tunnel ram , the Hemi had 3 tunnel rams , the Rat Roaster
, the Super Stock cross ram & the Nascar Bath tub intake which are all cross rams similar to
the long ram 300 intakes but with much shorter runners to work at higher rpm. The newer
engines like the 94 & up Magnums use the long tunnel ram intkaes with curved runners ,
commonly know as the barrel intakes as with the single plane intakes runner size & length &
plenum volume dictate the rpm range where intake works best at. There are also the
aftermarket race tunnel rams with very tall vertical runners & different tops for single
4 bbl with a relatively large plenum , or 2 4 bbls & plenum or IR applications where 2 4 bbls
are used & there is no plenum at all & each runner is mated to 1 bbl of a carb so each
cylinder can be individually tuned
essentially there are no good or bad intakes as each intake is specifically designed to work
in a given application with speicific cams & carbs 

Hot tip ... seing as most of these cars are not driven in the cold anymore using an intake
gasket that blocks the heat crossover port can be a big advantage on warm days
Part # 1214 for B engines & 1215 for RB , From Fel Pro

[blown motor]

Neil, great info but I'm a little green on some of this engine stuff. Can you please explain what you mean by "signal at the carb"?

[HP_Cuda]

Neil is referring to the vacuum of the motor.

More signal more draw, better fuel atomization.

This kinda can lead someone with a low vacuum motor (high cam profile) towards an annular discharge instead of a downleg carb as well.

Just food for thought.

[Chryco Psycho]

 
Thanks