Dart Builds The Ultimate Big Cube 440-Inch Small Block (Part 2)

If you have been following along at all (we know if you have or have not, kinda like Santa Claus), then you would know that we recently went through the process of building the bottom end of our 440 cubic-inch behemoth small-block dyno mule. The 440 is based on a Dart SHP block with a 4” stroke and 4.185” bore. The Dart block is the foundation for what will become a serious piece of test equipment, one that will sure ingest copious amounts of fuel and nitrous. Before any of that debauchery can happen, however, we need to finish building the engine.

The 440 short block was buttoned up with an ATI Super Damper

Playing Catchup

We have the rotating assembly handled with goodies like the forged Lunati crank and I-beam rods, now we need the soul of any engine- the camshaft. The cam is where all of the magic happens inside an engine. Sure, the crank is big and strong, it takes the abuse from explosions of fuel, pressure from boost and nitrous, but it only does that one thing.

The cam on the other hand is delicate; it doesn’t take much to wipe out a cam lobe, even the wrong oil. The camshaft controls the beat of the engine, how it sounds, how much power it makes.

The beauty of it is that the cam profile is easily changed, unlike the rest of the internal parts. One thing is for certain, the 440 is going to see quite a few different cams. For the baseline, however, we have spec’d out a nice little number from Comp Cams. Because a traditional small-block is 400 cubes or smaller, off the shelf cams are specified for those engine sizes, not exactly optimum for a 440 cubic-inch engine. That required us to depart from the catalog and order a custom grind.

We opted for a custom Comp hydraulic roller bumpstick with .579” of gross valve lift on the intake and exhaust sides with .381 of lobe lift, with 254 degrees of intake duration and 266 degrees on the output side of things. Loads of lift and the long duration mean that this should be one grumbly little small-block in the dyno cell. Since the 440 will likely see numerous cam swaps, we installed a 2-piece timing cover from Comp Cams. Not only does this aluminum cover eliminate flex that can cause erratic timing, but also makes for easy cam swaps without having to deal with the oil pan seal, which is quite nice for a test mule.

No cheap gaskets here, only the best with Fel-Pro's silicone gaskets

Dampening Our Spirits

Hanging off the front of the timing cover is an ATI Super Damper (917411) to settle all those nasty little harmonics that ping off the internals as they spin wildly at 6500 RPM. As we discussed in Part 1, there are all kinds of brutal forces happening inside the engine on the rotating assembly. At any given moment, the crank is pushing a piston up, pulling a piston down all the while another piston is pushing the crank down on its power stroke. This creates crankshaft twist; it robs power and breaks stuff. The damper is there to help absorb the torsional twist.

A poorly built or worn out damper will not absorb any of the twist, but a properly designed damper can absorb virtually all of it. The stock damper is designed to handle just that, a stock engine; it simply cannot handle a modified rotating assembly. Another issue with stock-style dampers is that they can come apart. We opted for the ATI SFI-approved damper for the 440 because the last thing we want is a stock-style damper to explode in the dyno cell.

Each of our cylinder heads were fully machined in the CNC machine shop, including a multi-angle valve job for superior flow.

Before final assembly, the piston to valve clearance was checked with clay

Getting A Head

The next part of the equation is the cylinder heads. The goal here is to make 550hp or more without boost or nitrous, so we need flow to generate that kind of power. When you start with 440 cubes, the power comes in pretty quick without much effort, but you still need the ability to get the air/fuel in and out of the motor in a hurry. Where the camshaft determines the attitude of the engine, the power potential is in the cylinder heads. If we were to stick a set of 291 “double hump” heads on this thing it would run, but not well. We needed a set of lungs that will not only make the 550hp baseline, but also help us test the other parts with reliable results. To do this, we selected a pair of Dart Pro 1 series small-block heads.

There are several versions of these heads, determined by the size of the intake port volume. Since we have a mammoth 440, we went with the equally large 215cc model. Dart does make a larger port SBC head, so why not choose it over the smaller volume? The answer is less than simple, but without getting too technical, here it is—a large port volume will yield more air flow, but at the cost of port velocity. One of the key components of building power is not only pushing as much air/fuel into the engine as possible, but also doing so quickly. This is where many beginners go wrong, they choose a head that is simply too big for the engine and power range they are going for.

The Dart Pro 1 heads were secured to the block with ARP head studs

We mounted a set of Comp Cams Magnum roller rockers. These steel rockers actually weigh less than most aluminum rockers.

Port velocity is the speed at which the air flows through the head. The larger the port volume, the slower the air will move because it doesn’t have to; tighten up the volume and you can flow almost the same amount of air, but it will be moving faster. According to Dart’s website, a projected horsepower range from 500-550 will require between 200 and 220 CC of port volume. Less volume will choke the engine, more will bog it down. These do not necessarily apply to boosted engines, as the air is forced into the engine, not relying on vacuum and atmospheric pressure. The valves on the Dart Pro1 heads are 2.05” intake and 1.60” exhaust, featuring a multi-angle valve job in the intake seat to increase the flow.

Each head is CNC machined to exacting tolerances to ensure each head will match side by side. In as-cast trim, the Pro 1 215cc heads flow 276 cfm @ .600” lift @28” of water, which should provide enough air for our 440 to breathe. We stuck with the 72cc combustion chambers to keep the 440 pump-gas friendly with a 10.1:1 compression ratio, which is one of our main goals.

Dart's aluminum single plane intake is specifically designed to mesh with Dart heads without massaging the ports

The intake was mounted using ARP stainless steel fasteners. We also tried out a few phenolic carb spacers

Top End Reflections

The cylinder heads were mated to the 440 block with a set of Fel-Pro head gaskets between them. Securing the heads is a set of ARP head studs (234-4301). If you have never used head studs, we highly recommend them, they are so choice. Unless you have an 80s GM G-body with AC and need to the pull the heads with the motor in the car. Then you will be cursing yourself. Just sayin’.

Before we torqued the heads down for the final installation, we laid some clay out on the #1 piston, set up a pair of rockers on the #1 cylinder and slowly turned over the motor. Once we had gone a full rotation, we pulled the head to check for valve clearance. This is a crucial step.

We tried a couple of carbs, but ended up sticking with the ProForm 850

Even though we knew that all the specs were dialed in for the theoretical application, you should always check this because it is much easier to fix it now than it is after you hit the starter and frag it all because a valve nicked a piston.

At this point, the valve train could be completed. We went with a set of Comp Cams Magnum roller rockers and roller lifters (190-195-210 and 98891-16, respectively) to compliment that sweet custom camshaft we installed earlier. The valvetrain is an easy place to gain or lose power, so choosing the right parts is critical. The stock rocker arm is a stamped steel POS, so when you are talking about high horsepower numbers, those are automatically out. Reducing friction is the fastest way to gain power, because friction means heat and heat kills everything.

In the valvetrain, “roller” is the key. In this case, roller means roller bearings. Bearings reduce the friction between moving parts. Roller rockers come in two flavors: roller tip and full roller.

Roller tip rockers have a standard trunion (the part that rocks on the rocker stud) with a roller on the, you guessed it, tip, where the rocker meets the valve stem. This reduces one friction point as well as provides a more consistent footprint on the valve. Full roller rockers have needle-bearing trunions and roller tips. Then there is the whole steel vs. aluminum debate on rocker arms.

In the past, aluminum rocker arms got a bad rap because aluminum requires more meat around the bearings, which limits the size of the bearings. This leads to premature failure, where the rocker could literally split in half.

We capped off the 440 with a ProForm 850 cfm carb and a Mallory distributor

Comp Cams has developed aluminum rocker arms that use precision needle bearings that can withstand 350 ft lbs of spring pressure. They are so sure of their aluminum rockers (called Ultra Golds) that they provide a lifetime warranty on each set. Weight is important in a rocker arm because of the moment of inertia. This is the rocker arm’s resistance to rotation.

As the moment of inertia increases, more valve spring pressure is required to control the rocker arm (as opposed to the valve). This robs horsepower and RPM. Reducing the weight on the rocker, particularly away from the trunion, reduces the moment of inertia. In the end, we decided to go with a set of Comp’s Ultra Pro Magnum steel rockers.

These bad boys are made of 8650 chromemoly with strengthening ribs (to help cut the weight) and feature a sporty black oxide finish that resists corrosion. These steel rockers actually weigh a little less than the Ultra Gold aluminum rockers due to their unique webbed design. Because they are steel, there is also a little more room for valve spring and retainer clearance.

The 440 was plumbed and wired to the dyno cell, just about time for some power pulls.

To The Nth Degree

Once the rockers were installed, the Dart assembly team bolted on the degree wheel. Any performance engine camshaft should be degreed. There are numerous influencers on the accuracy of the cam timing; degreeing takes those factors out of the equation, ensuring the valve timing events occur when they are supposed to. Influencers include camshaft variance, timing chain stretch, crank keyway variance, and dowel hole alignment, and can serve to alter the cam timing.

To properly degree a camshaft, you need a degree kit that includes a degree wheel, dial indicator and base, piston stop, checking springs and the pointer. There are two main methods of degreeing a cam, the centerline method and the .050” lift method. Most builders agree that the .050” lift method is the most accurate, and because we are talking about checking accuracy in the first place, that is the method we used.

Topping off the heads is a Dart single-plane intake (42411000) which was designed to work specifically with the Dart heads. The intake runners are matched to the cylinder heads, so that you have optimum flow potential with as few bottlenecks as possible. The intake comes with bosses at all four corners for equalized coolant flow, which is a cool feature in a street/strip car. When used, this allows the coolant pressure to be equalized between the cylinder heads and helps to eliminate air pockets that can make cooling an engine impossible.

The dyno cell is a little more complicated than the dashboard of a ’65 Chevelle.

Another neat feature of the Dart intake is the dual distributor hold downs, one on each side, making timing changes nice and easy. We sealed the intake to the heads using more Fel-Pro gaskets and a set of trick ARP stainless steel bolts.

The bolts look great and have 12-point heads, so they don’t strip out and you don’t need a big socket that gets in the way, just a 3/8” on a wobble joint and you have no problems reaching the center bolts.

We filled the motor with a little break-in oil from Comp Cams and used a cordless drill to pre-lube the oiling system. Even though we are using a roller cam, it is still a good idea to use proper break-in oil with extra ZDDP to protect the internal parts on the initial start-up. Then the slick cast aluminum DART-emblazoned valve covers were installed, held in place by, yup, more ARP stainless steel fasteners. We also bolted on a water neck so the coolant doesn’t just spill out on the floor.

On The Dyno

On top of the intake we mounted a ProForm 850 CFM carburetor direct to the aluminum. During the dyno test and tune, we will be trying out some spacers, but for now, this carb is ridin’ commando. Another classic gearhead mistake is running too much carb. Even though the 440 is in big-block cubic inch territory, we don’t need a massive carburetor, at least not yet. This mule is naturally aspirated; it doesn’t need massive amounts of air to make plenty of power. Part of that is in the cylinder head design, and the camshaft profile, it just isn’t necessary for what we have planned.

There is always room for improvement. Using the dyno results, the team was able to make some timing and jet changes to extract the most power

There is a simple formula that makes it easy to choose the right carb size (cubic inches x RPM X volumetric efficiency)/3456 = CFM. Volumetric efficiency is the red herring here, but in general terms (VE is expressed in percentages, 100%=1, 90%=.90), a stock motor will be in the .8 range, a performance motor in the .9 range and a boosted engine will be above 1. We have seen naturally aspirated street/strip engines at the dyno push out 110% efficiency, so there is some room for error in the initial calculation without dyno numbers showing the actual efficiency.

The VE limit for a naturally aspirated engine is 137%. We are going to peg our 440 at 95%, which is a realistic number. If we punch in 440 x 6500 (that’s our redline) x .95 and divide that by the magic number (3456), then we see that 786 CFM will do the trick. If the engine turns out to be less efficient, 800 CFM be needed, but that is what tuning is for.

With that, we dropped in the Mallory Comp SS distributor (4248211) and hooked it all up to the Westtech dyno cell for the initial break-in and a few test pulls. After several test runs, we set the distributor to 36-degrees of total timing, no spacer, and the 850 carb. The 440 made good numbers, already hitting our desired spec and passing it by 20 ponies for a total of 570.3 @6200 RPM, while spitting out 545 tire-smoking ft lbs @ 5000 RPM.

So, What’s Next?

Is there more power lurking deep inside the Dart 440? What is it going to take to get 600 out of this plus-size small block? There is definitely more to come from our new dyno mule, we know that for sure. With everything this little monster has inside, we’re figuring on ramping up the numbers with a solid camshaft, lifters and maybe even some more carburetion.

Oh, who are we fooling? We went ahead and did a shootout between our current setup and a solid roller and race carb setup HERE. Trust us, you’ll like what you’ll see.

While so much of the automotive industry wants to make you think that the LS is taking the world by storm, we love that our old school small block Chevy can make some serious horsepower using some really unique and forward-thinking components from Dart, Lunati, Comp and ATI. We’ll be regularly flogging our little powder keg again and again, so make sure to key an eye out.


About the author

Jefferson Bryant

It is almost terrifying the breadth of Jefferson's technical abilities. A fabricator, master technician, engine builder, paint and body guy, dirt track racer, road course driver, or a glossy magazine reporter, Jefferson can do it all. Oh yeah, he's also a YouTube hero.
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