Let's face it, there's a ton of aftermarket intakes out there, from mild to just plain
wild.
But how do you know which one is the right one for your engine?
Choosing the correct intake manifold can pay huge dividends with increased power and additional
torque for your engine but only if you make an educated decision.
Let's take a quick look at a stock intake manifold.
The plenum on a stock intake manifold is typically on the smaller side.
This helps keep the air velocity high.
Likewise, the cross-section of the runners is also fairly small, this keeps the air moving
at maximum speed and the fuel atomized going into the cylinders.
These small runners provide good idle quality and crisp throttle response but the smaller
size also limits the amount of air that the manifold can flow, especially at higher RPMs.
Eventually, the engine is going to reach a point where it's trying to pull in more air
than the stock intake can actually flow.
This is the point at which a stock intake manifold needs to be upgraded to a performance
manifold with a larger plenum and larger runners.
As with most situations, when building an engine, the intake manifold should be matched
to your intended purpose for your engine.
Be sure to consider the engine combination that your building or already have.
Will your project be a daily driver or is it going to be a weekend warrior for the strip
or the track?
These are some important questions to ask yourself, so be realistic with your answers.
Throwing a bunch of mismatch parts at your engine more than likely isn't going to give
you the performance that you are looking for.
Everyone likes the look of a big tunnel ram but it's probably not the most practical set
up for your weekend cruiser.
Intake manufacturers advertise RPM ranges, identifying where their intakes are the most
efficient.
For example, an intake manufacturer may advertise a range of 1500 to 6500 RPMs.
Taking into consideration this advertised RPM range is one of the easiest guides to
use when choosing the right intake for your engine.
Most street cars seem to work best with a dual plane intake and most advertise in a
PRM range of idle to 6000 RPMs or even a 1500 to 6500 RPMs.
Simply because that's the RPM range that they're running at most of the time.
Race cars typically produce their power more in the upper RPM ranges and will require a
single plane intake with a 2500 to 8000 RPM range.
You also need to consider the physical fitment.
Be sure to select the appropriate part number for your engine and cylinder head design and
look for any specific features that you may need like engine vacuum ports, water coolant
ports, carburetor flange fitment, and don't forget to check for proper hood clearance
before you close the hood.
Let's take a look at the dual plane intake.
They are named for the split plenum opening just below where the carburetor sits and each
side of this opening feeds four of the cylinders on a V8.
Dual plane intakes are popular on performance street and some mild racing applications since
they generally build power across a wider RPM range starting at idle to 1500 RPMs depending
on the manifold.
Every intake has it's own performance characteristics so it's best to know how you plan to use your
vehicle and select an intake from there.
Holley and Weiand carry a wide variety of dual plane intakes in several configurations
including two by four and three by two setups.
They're an excellent choice for performance intake in this RPM range.
In a single plane intake, all the cylinders share the same intake plenum.
Fuel and air from the carburetor enters the intake from this one opening without any separation,
unlike the dual plane.
This single hole feeds all eight cylinders on a V8.
Single plane intakes are typically less restrictive and work best for building power between 3000
and 8000 RPMs.
Because of the higher RPM ranges, the single plane intake manifold is best suited for racing
applications and not so much for your daily driver.
Holley's stripped Dominator and Weiand's Accelerator, Track Warrior, and Team G intakes are excellent
intakes designed to perform in this power band range.
If you are looking for something a little more outside the box, then check out Weiand's
line of Hi-Ram intakes.
They're a nostalgic looking single plane intake that you can either run a single or a four
barrel setup with, and a more modern look can be had with one of our Sniper sheet metal
fabricated intakes.
They too are available in single or dual four-barrel configurations.
You may also hear the term low-rise and high-rise manifold.
Both of these terms refer to the overall height of the intake manifold, but they can also
help identify the RPM range that they work best in.
There is no standard or set height where the low-rise intakes end and the high-rise intakes
begin, but low-rise manifolds are usually similar in height to a stock intake's dimensions.
They offer good head clearance, and most applications allow you to build your combination without
having to cut a hole in your hood or adding a hood scoop.
Low-rise can also identify the runner length and RPM range as well.
The shorter, closer to stock length runners will perform closer to the factory specs and
also offer great throttle response right off idle and throughout the RPM range.
High-rise intakes, on the other hand, are better for building horsepower in the upper
RPM range and typically have larger and longer intake runners.
The power band of a high-rise usually starts around 2700 to 3000 RPMs and they can be capable
of making power all the way through 7000 to even 8000 RPMs.
The last bit of information that you are going to need to consider when selecting your intake
manifold depends directly on which carburetor or throttle body that you plan to use.
For street, you'll likely find two choices of mounting flanges.
First is the 4150 or commonly referred to as a square bore style.
This design uses four holes of equal size or you may see that it has one large square
hole or even two elongated holes for the intake opening.
They are designed to work with a wide variety of Holley, Quick Fuel, Brawler, and Demon
carburetors with the 4150 flange.
The second design is called the spread bore.
It can have four holes or you may find a spread bore with a large single hole or even two
elongated holes, but if you look closer, you'll see that the openings are larger towards the
rear portion.
If we take a look at this Holley spread bore carburetor, you'll notice that the front holes
are the primary venturis are smaller in diameter when compared to the rear or secondary holes.
The odd shape of these intakes allows clearance for the larger secondary venturis found on
the spread bore carburetors.
If you happen to find a manifold you like but it's not available for your particular
carburetor, there are plenty of adapters available to mount a square bore carb to a spread bore
intake and vise-versa.
The third choice you'll run into is the 4500 or Dominator style intake, these are typically
single plane intakes and they are designed for racing or high horsepower applications.
They have the much larger 4500 style mounting flange which allows you to mount one of our
Dominator carburetors too.
So now that we've covered the basics, you can see just how important intake manifold
selection is.
Remember, match the RPM range of the manifold with the RPM range of your other engine components
and you'll be happier in the long run and so will your engine.
Thanks for watching and to see our full line of intake manifolds and intake accessories,
visit our website at Holley.com