Like any good cliff-hanger, when we left you last month, our Anti-LS small-block engine was well underway at Dart Machinery. But would we be able to do what we set out to? Could we build a Gen I small-block Chevy that could run with the new favored-son LS engines? Would it be streetable? Dependable? Would Charlie finally ask Diane to marry him? Wait, wrong soap opera.
We reconvened with Jack McInnis, Tony McAfee, and Jeff Lake at Dart to finish the build and dyno test the small-block to see if we had a winner, or wishful thinking. Last month, the crew at Dart machined and assembled a stout SHP short-block as the foundation for our anti-LS engine. Using the company’s iron SHP block with a 4.000-inch bore, they tossed in a 3.750-inch Eagle crank, CompStar steel H-beam rods, Mahle flat-top pistons and a COMP Cams solid-roller camshaft.
We detailed the components and assembly in this Dart SHP 427 short-block last month. In ca
With 427 ci in the short-block and a camshaft worthy of its solid roller construction, this engine needed a pair of cylinder heads that could deliver a healthy volume of air/fuel mixture. We had two additional requirements for the cylinder heads. First, they needed to be a traditional 23-degree design with stock valve and port locations. That way a regular intake manifold and headers would bolt up; in fact, the whole exhaust system that is already in our Laguna should reattach nicely. Second, they had to flow like tax dollars into the national debt right out of the box. By avoiding hand porting, we’re building an engine that you can duplicate exactly with off-the-shelf parts. You can thank us later. The Dart Pro 1 CNC heads were exactly what we were looking for. They are fully CNC machined for precision, and the intake ports are a massive 227 cc. At .700-inch lift, the intakes will flow 309 cfm, and we’re in that ballpark at .688 inch of lift at the valve with our COMP Cams roller camshaft and 1.6:1 rocker arms. The exhaust side is matched proportionally to the intake, with 226 cfm at .700-inch lift.
For the most part, the valvetrain in this 427 is made up of COMP Cams matched components. We like this approach because the cam manufacturer generally has a good matched set of valvesprings, and all of the related parts such as lifters and pushrods are designed to play nicely with each other. The only valvetrain parts that are not from COMP are the 2.08/1.60-inch valves and adjustable guideplates, which all came from Dart.
We introduced you to our custom bumpstick last month, but the specs merit repeating here. The intake lobes sport 259 degrees of duration at .050-inch lift while the exhaust side has 268 degrees. Lobe separation is 108 degrees, and lift on both lobes is .430 inch, which gives us a gross lift of .688 inch with the COMP Cams Ultra Pro Magnum 1.6 rocker arms. This camshaft is aggressive for the street by most people’s standards, but this engine isn’t meant to be a docile, smooth idle, high-vacuum and otherwise yawn-inspiring small-block. We’re pushing the envelope of streetable power and with that comes a higher, rougher idle, and getting intimate with the fine line of durability. This engine won’t require a ton of maintenance, but checking the valve lash twice a year will let you know if any of your valvetrain parts are wearing and need attention.
The Dart SHP block has rod-clearance notches for big stroke applications, and it locates t
To button up the bottom end, we ordered a Moroso oil pan and oil pump. When you order a pu
We chose a TCI Rattler 2000 damper for this engine build. The Rattler is designed to absor
We chose a TCI Rattler 2000 damper for this engine build. The Rattler is designed to absor
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, we will use a TCI flexplate to fit our automatic trans in the L
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 pan on, the oil pan gaskets needed to be cut. Using a permane
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, we could turn the engine over and assemble the rest of the
It takes pretty big cylinder heads to feed a 427ci small-block. The intake and exhaust por
These heads also feature fully CNC-machined 227cc intake ports that flow 309 cfm at .700-i
Tony installed the Dart Pro 1 heads with ARP head bolts. Some people might prefer head stu
The exhaust side flows 226 cfm at .700-inch lift, which is a very nice balance with the in
These Fel-Pro 1004 head gaskets have 4.190-inch bore openings and a compressed thickness o
We used COMP Cams’ Ultra Pro Magnum 1.6 rocker arms on both the intake and exhaust for a t
This is how good the CNC work is on the Dart Pro 1 heads: The 1206 Fel-Pro intake gaskets
Tony installed a set of Dart adjustable guideplates on the engine. These interlocking plat
The Dart single-plane intake manifold is meant for high-rpm, no-nonsense engines like our
For ignition on the dyno and also in our Laguna, we chose a Performance Distributors HEI.
One of the coolest features on the Performance Distributors HEI is the instant timing knob
While we didn’t need a water pump on the dyno, we’ll need one when the engine is dropped i
We got our hands on two of the brand-new Holley Ultra HP carburetors: one a 850 cfm (left)
Where The Money Went
|*Prices from Summit Racing
|Dart 427 SHP short-block (assembled)
|COMP Cams solid-roller camshaft custom grind
|COMP Cams billet double-roller timing set
|ARP head bolt kit
|ARP oil pump stud kit
|COMP Cams valvesprings
|COMP Cams Ultra Pro Magnum 1.6:1 roller rockers
|COMP Cams three-piece timing cover
|COMP Cams lightweight tool steel retainers
|COMP Cams super valve locks
|COMP Cams Endure-X lifters
|COMP Cams pushrods
|Fel-Pro head gasket
|Fel-Pro intake gasket
|Fel-Pro gasket set
|Dart Pro 1 CNC cylinder heads, bare
|Dart 2.08-inch intake valves
|Dart 1.60-inch exhaust valves
|Dart single-plane small-block Chevy intake manifold
|Holley Ultra HP 850 carburetor
|HVH 2-inch Super Sucker carb spacer
|Moroso oil pump and pickup kit
|DUI distributor with instant timing knob
|Performance Distributors LiveWires
|TCI 168-tooth SFI-spec Flexplate
|TCI Rattler 6¼-inch Chevy small-block damper
|Weiand Team G aluminum water pump
On The Dyno - Dart Shp 427ci