Power and combustion depends on three key factors: fuel, spark, and oxygen. Since the first fossil fuel vehicles hit the race track, engineers and designers have been working on the most efficient ways to funnel the earth’s atmosphere into the combustion chamber, and we’ve come a long way since then.
The magic sauce has long been the intake manifold, where the air is distributed – often not perfectly – from a common plenum to individual runners in the cylinder heads. Intake manifold technology has come a long way, from OEM composite designs to the latest in racing trends – billet and sheetmetal materials and CAD/CNC design. After all – with today’s technology – you can design and machine anything with the click of a mouse.
Utilizing the modern 5-axis CNC machines of today, wizards like the ones at Wilson Manifolds and Steve Morris Engines are able to shape aluminum in new and different ways – taking a new approach to optimizing airflow. In many ways, the tools and materials today allow top intake designers to make curves, bends, and profiles that were either very difficult, or in some cases, impossible with raw flat sheetmetal.
There are a five different styles of intakes available in the market now:
- Cast Aluminum Intake
- Composite/Plastic Intake (primarily OEM)
- Sheet metal Aluminum Intake
- Sheet metal/Billet Hybrid Intake
- All-Billet Intake
We all know the cast aluminum intake manifold – familiar and generally inflexible when it comes to making major optimizations without lots of welding. It works great for many racing applications and street applications, but is limited for high-end racing applications.
The composite/plastic intake which is OEM on Modular and LS engines (and available from FAST for LS engines) is similar to the cast intake in that it can’t be easily modified, but offers some advantages in street applications.
Next up is sheetmetal aluminum intake setup, which has been a tried and true intake combination that carries the benefits of a custom designed manifold and a lower hit to the pocket book. This was the standard bearer in racing manifolds for many years. These intakes are custom designed and fabricated from sheetmetal sheets.
Hybrid billet/sheetmetal intakes combine with some billet portions and some sheetmetal portions. These can be highly effective and in many racing applications are both more cost effective and as equally effective as full billet intakes.
On the top end, is the All-Billet intake. The billet intake design can be practically anything you dream up. It offers the ultimate in customization and in some cases, is the only option in terms of the shape and contours that the engineering/designer is looking for.
In this article, we take a deep look into the mechanics of custom billet and sheetmetal intakes with the help of the experts, Rob Mansfield, Justin Beard, and Keith Wilson, at Wilson and the engine master Steve Morris himself.
The Theory Of Pulling Horsepower Out Of Thin Air
When it comes to intake design, Steve Morris told us that manufactures take a strategic approach to constructing and tuning the flow of an intake for a particular set of goals. During our discussions we highlighted the reasons why someone would consider going with a custom manifold design. Wilson told us that an intake manifold is much like a camshaft, meaning that it’s practically infinitely adjustable. To make most of the intake design, Wilson says have to look at the entire combination, everything from big details like power adder, cubic inches, rpm range, and cam profile, to smaller things like compression, ring packages, and engine efficiency.
“Usually, our billet manifolds, or high-end difficult to manufacture manifolds are for professional teams, or a particular situation, where a design is pretty much optimized,” said Keith Wilson. “At that level, you’re basically designing from a clean sheet of paper, and taking all of those facts from the engine builder and constructing it for a certain application. The weight of the vehicle, the RPM range, power adder or no power adder, you look at everything. It depends on where you’re racing. There are so many variables; to write an equation that works for every single application is impossible.”
Wilson says there are still some general intake rules to play by if an engine is going to be a high-revving or a specific displacement drag racing engine. For example, for the high-end naturally aspirated machines you see in NHRA Pro Stock, a certain runner length is ideal and has been science’d out using a mixture of experience, testing, and engineering.
“Any engine that’s built professionally for drag racing only has a 1,500 to 2,000 rpm window that the engine’s going to operate at… meaning gear drop,” explained Beard at Wilson Manifolds. “So you’re not going to engineer an 11,000 rpm manifold to run at 6,000 rpm. You’re going to need to look at what operating rpm the vehicle’s going to be, and where the converter locks up, or where the clutch starts slipping, etc. You’re going to need to take all of this into consideration.”
Wilson explained that it doesn’t matter the form of racing we are building and engine for, the engine is constantly fighting one obstacle. In many cases, especially where you see extreme racing environments like drag racing, NASCAR, and F1 – an intake manifold is often partially designed around the ‘worst’ cylinder. As such, the experts at both Wilson and Steve Morris have spent countless hours on the flow bench to optimize intake design.
“You could ruin a really good cylinder head combination just by improperly sizing a manifolds taper or length. It could turn into a very big restriction,” Wilson explained. “You get limited by your worst cylinder, so now you’re having a hard time tuning to the edge, because you have one cylinder that’s haunting you, and you can’t push the combination as far as you would like to.”
During these sessions, they are looking a more than just total flow numbers. To achieve optimal performance the whole port needs to be balanced in in what Wilson says is ‘feet per second’. Wilson pays a massive amount of attention in this particular area. If you do have a boosted power adder in a drag application, you often times don’t have that one hole that’s haunting you all the time quite a much. This helps an engine tuner push a combination to the edge without hurting something. It has become common place for people to assume that an intake is a mere addition to a cylinder head, and it’s not the cylinder head designers main concentration.
As a result, our experts explained that some cylinder head designers don’t always take into account how the intake manifold works and what effect is has to the cylinder head. Essentially, the consensus is that the manifold can drive the efficiency and effectiveness of the port in the cylinder head, but it’s often overlooked. On the bad side, in some situations, the manifold can be a restriction on very good cylinder head, if not properly designed.
Constructing A Masterful Intake
We have enlisted both of these leaders in the industry on both our Dragzine Project cars. We worked tirelessly with Wilson Manifolds to construct a hybrid intake that would carry our BlownZ Camaro to new records, while Steve Morris Engines is currently prepping an engine and billet manifold for our Evil 8.5 Fox body Mustang project build.
“Naturally, we want you guys to be fast. We worked on your manifold very hard, and the shape that we came up with is what we would want,” Wilson explained when the intake for BlownZ’s LME-built 441ci ProCharger Engine came up discussion. “If it were a billet piece, it would have a few more contours in there. But you wouldn’t see any difference in flow.”
The diehard gearheads at Wilson continued with say, “There are cases where for example in a race boat we just finished, and we had to do the top out of billet, where the throttle-body had to be located. There are some limitations that we would rather do it out of CNC billet, and then it’s worth the cost. But for you guys on that application, it wasn’t something we had to do. If we had cut the same thing, and the throttle-body was left in the same location, we wouldn’t see any power gain.”
“When it comes to sheetmetal and billet hybrids, you have a really nice set of billet runners, that can be machined to a precise taper or exact runner volume, attached to a fabricated upper which helps keep the cost down. Considering you could have over $1,000 in material cost alone when it comes to fully billet pieces, it is often more feasible and cost effective to go with this hybrid setup.”
Steve Morris: Going All-In with Billet
When it comes to billet, it can only machine what the tool bit is able to reach. Whereas in a fabricated piece you are only limited by the ability to weld the portion of the intake into place.”- Steve Morris
“With these billet pieces, what people who don’t machine for a living don’t understand is, there are limitations to what can be done. In layman’s terms, if you can’t reach the area with your finger it’s going to difficult to machine,” Steve Morris shared with us.
“When it comes to billet, it can only machine what the tool bit is able to reach. Whereas in a fabricated piece you are only limited by the ability to weld the portion of the intake into place.”
While billet CNC milled pieces bring an additional amount of cost to the table, the designers and machinists are able to control wall thickness throughout the entire intake. Morris says this minimizes the potential of intake failures, due to a weld failing of in a particular area of the manifold.
“When I started doing manifolds, I made the conscious decision produce only fully CNC’d items, instead of doing sheetmetal or billet-sheetmetal hybrids,” Steve Morris explained. “The reasoning behind this plan of attack was that we feel we have better control over the shapes and designs of the intakes key components, with the added benefit of being more structurally sound.
Wilson also makes all-billet intakes, but seems to have an alternate thought process about the necessity for billet material in many applications. It’s an interesting dialog, in that Wilson and Steve Morris are both well known for intake manifolds, but in many ways, may endorse two different paths to the same objective.
As mentioned, Morris is also building our 427ci small-block Chevy engine that will power our Fox-body with the help of a Vortech Xi-billet Supercharger. (Read about it here). This is the engine that will also get the Morris billet intake. It is designed to work with the Brodix BD-2300 heads we will be running. We will have a full-story coming soon on the engine build that will tell you more about the intake and power numbers.
When you’re looking to create a devastating wake of passes or crushing the current world-record, a custom build intake is at the front lines to provide the intake supply your engine needs. Whether you pick a sheetmetal intake, a hybrid, or a full billet manifold, you should be better equipped to understand the strengths and advantages of each design, as well as the cost.
One thing we know — the airflow experts at Wilson Manifolds and Steve Morris are dedicated to ensuring that cylinder heads are provided with an even supply of air, thanks to a massive amount of research and development. We hope you’ve gained more of an understanding of what it takes to construct a world-class intake manifold and what the benefits are to these one-off pieces.