We chose a TCI Rattler 2000...
We chose a TCI Rattler 2000 damper for this engine build. The Rattler is designed to absorb torsional vibration with an internal pendulum absorber. It doesn’t have any components that will wear or age, so it requires no maintenance or periodic rebuilding. It’s also one of the lightest dampers available.
Enough with the disclaimers and onward to making the kind of power that every small-block Chevy owner dreams of. With the cylinder heads and valvetrain selected, it was time to pick out some induction components. The perfect match for the Dart Pro 1 CNC heads is the Dart single-plane intake. This intake features extended runner dividers inside the plenum to equalize port length. They are also radiused with the angled runners to move massive amounts of air/fuel mixture to the individual intake ports of the heads. To top off the intake, we used a brand-new Holley Ultra HP carburetor. This latest version of the Holley carb features countless new features, which will make tuning for the street and various types of racing we plan on doing easier than ever. Some of our favorite features are the aluminum construction that makes the carb about 30 percent lighter than a traditional 4150-style double pumper, internal baffles in the fuel bowl that will help control fuel slosh, adjustable secondary link, billet metering blocks with integrated pry-point, and the ultracool Hard Core Gray hard coat anodized finish. These may become our new favorite carbs. With the engine size, cam specs, and head volume, there was debate on whether an 850- or 950-cfm carb would make the most power on the dyno, so we tested both.
At the rear of the engine,...
At the rear of the engine, we will use a TCI flexplate to fit our automatic trans in the Laguna. This steel flexplate is made in the USA and SFI spec’d, which will be important for us when we hit the racetrack. The Dart SHP small-block Chevy engines are all internally balanced, making the selection of dampers and flexplates/flywheels that can be used very generous.
The last thing we needed before we could light the fire in this thing was an igniter. We love the simplicity of an HEI, and having all of our ignition components under a single cap, so we called Performance Distributors and Steve Davis recommended that we try his latest distributor. It has all the features of his standard HEI system, but has a unique instant timing knob that lets you adjust the timing by turning the knob, and a slip collar so it can be used with a variety of deck heights and intake manifold types. These new features add about $210 to the price of a regular Performance Distributor HEI, so consider that when you review the “Where the Money Went” sidebar.
With that, it was time to shelf the bench racing, put spark to fuel, and watch the dyno needles dance to see what this big-inch small-block could produce. With its first breath, this engine seemed eager to prove its worth. Check out “Let’s Rock!” to read about the results we found during our dyno session.
Before we could bolt the oil...
Before we could bolt the oil pan on, the oil pan gaskets needed to be cut. Using a permanent marker, Jeff noted the location of each of the rod-clearance notches in the pan rail. The guys at Dart have a really cool tool for cleaning cutting sections of gasket away, but we can manage with a razor blade and a flat surface.
Enough talk about the parts, what’s all of this worth in terms of pump-gas power? We strapped the big-inch small-block SHP 427 to Dart’s dyno and made a dozen pulls. From the first time spark hit fuel in the cylinders, we realized just how potent this engine was. It sounds plain angry, even as it idles down to about 900 rpm.
Our goal was to crest the 600hp mark with a Gen I motor that had enough durability and manners to be driven on the street. The Dart SHP 427 bettered that goal on the first pass. By the end of the day, we had captured an extremely respectful 627 hp with an equally impressive 561 lb-ft of torque! That’ll get your attention.
We tried both an 850-cfm Holley Ultra HP carburetor and a 950 version in case the engine wanted even more fuel at the top end. The power numbers were pretty similar throughout the powerband with both carbs, but ultimately the 850 made more power, confirming that it’s the right size for this combination.
With a peak horsepower of 627, we surpassed our goal for this Gen I motor, proving that an engine doesn’t have to start with the letters “LS” to make serious power. We can pass this Chevy-orange beast off as a 305 or 350, or proudly proclaim its true displacement of 427 ci. And the best part is that it will bolt to our existing accessories, exhaust, and transmission.
With the oil pan on the engine,...
With the oil pan on the engine, we could turn the engine over and assemble the rest of the valvetrain. We’re using a COMP Cams solid roller cam with 259 degrees of duration at .050-inch lift on the intake and 268 degrees on the exhaust, and 0.688-inch lift with 1.6:1 rocker arms. We used COMP Cams’ Endure-X solid roller lifters.
It takes pretty big cylinder...
It takes pretty big cylinder heads to feed a 427ci small-block. The intake and exhaust ports, valve bowls, and combustion chambers on these Dart Pro 1 CNC heads are 100 percent CNC machined for precision and consistency. The heads have standard valve angle and spacing, as well as standard port location, so you can use off-the-shelf parts.
These heads also feature fully...
These heads also feature fully CNC-machined 227cc intake ports that flow 309 cfm at .700-inch lift. That’s pretty impressive considering these are standard 23-degree cylinder heads. They can be ported for even higher flow, but we wanted to demonstrate the power that’s possible without any hand-done work. The combustion chambers are a tight 66 cc, which is perfect for the higher street compression ratio we are aiming for.
Tony installed the Dart Pro...
Tony installed the Dart Pro 1 heads with ARP head bolts. Some people might prefer head studs for an engine of this compression and horsepower level, which is a viable option. Since these heads keep the valves and ports in the standard positions, traditional intake manifolds and headers will bolt right up. They also have commonly used accessory holes so the engine should accept all of your current accessories and brackets. No LS engine swap challenges here.
The exhaust side flows 226...
The exhaust side flows 226 cfm at .700-inch lift, which is a very nice balance with the intake port flow. The valve size is 2.08/1.60 inches, and the heads are available bare or fully assembled. We did a hybrid, having Dart provide the valves and using COMP Cams’ valvesprings, keepers, and retainers to match the COMP roller camshaft.
These Fel-Pro 1004 head gaskets...
These Fel-Pro 1004 head gaskets have 4.190-inch bore openings and a compressed thickness of .041 inch and a volume of 9.2 cc. They feature a pre-flattened steel wire seal that keeps a tight seal, even on a high-compression engine like this one. The final compression ratio with our combination of pistons, cylinder heads, and gasket is 10.8:1. With our cam profile and aluminum heads, detonation on the street won’t be a problem as long as we run 91 or better octane.