One of Dart’s newest products...
One of Dart’s newest products is its assembly lube. The lube contains zinc, moly, and other high-pressure additives to protect your new parts during assembly and break-in. All of the friction surfaces of the bearings are coated with the lube prior to setting the crank in place.
We drummed up a conversation with Jack McInnis and Tony McAfee at Dart to see what it would take to shift that 550hp number north of 600 while still having an engine that would run on pump gas and be durable on the street. Those of you who follow our Laguna project know that we enjoy tossing the two-ton Betty into the corners on autocross and road race courses, but it spends more than its fair share of time in Los Angeles traffic. McInnis and McAfee thought that a bit more compression and camshaft will be sufficient to push the 427 SHP over the 600 mark without creating a hand grenade with the pin pulled.
There are definitely some things you should realize about an engine like this. That kind of horsepower and torque will plaster a smile on your face that will make your girlfriend jealous. But it’s not a docile, smooth idling, 25-mpg mill. It’s going to have a lumpy idle, low vacuum for accessories, and scare small children. We’ll have no problems tolerating it in bumper-to-bumper traffic in SoCal, but not everyone would. With that reality check out of the way, we stopped by Dart in Troy, Michigan, to photograph the drool-worthy parts that would make up the short-block of this potent anti LS engine.
| Where the Money Went |
|
| Description: |
Source: |
PN: |
Price: |
| Dart 427 SHP short-block (assembled) |
Dart/Summit |
3124272 |
$5,397.73 |
| COMP Cams solid-roller camshaft custom grind |
COMP/Summit |
CCA-12-000-9 |
$324 |
| COMP Cams billet double-roller timing set |
COMP/Summit |
CCA-7100 |
$95 |
With the splayed main caps...
With the splayed main caps torqued, McAfee checks the crank endplay. Ours came in at 0.006 inch, which is within the target that McAfee likes to see for an automatic transmission application.
With the splayed main caps...
With the splayed main caps torqued, McAfee checks the crank endplay. Ours came in at 0.006 inch, which is within the target that McAfee likes to see for an automatic transmission application.
The COMP Cams roller camshaft...
The COMP Cams roller camshaft requires either a bronze or composite gear on the distributor. We’re using a Performance Distributors ignition system, and ordered the distributor with one of the company’s composite gears. These tend to last longer than the bronze gears, and they do not send bits of bronze through the engine as they wear.
The lobe separation is 108...
The lobe separation is 108 degrees, and we ordered a reduced based circle camshaft for added rod clearance; this is a must with a 4.000-inch stroke. We’ll fill you in on the rest of the valvetrain next month when we build the top end of this engine and stick it on the dyno to see if we’ll reach our 600hp goal.
We love COMP’s billet timing...
We love COMP’s billet timing set. Beyond robust parts that look and feel great, these double-roller timing sets make it super easy to degree the cam. Pull the lower gear off and select the crank keyway with the desired amount of advance or retard in cam timing, then line up the appropriate gear tooth with the dot on the cam gear. The roller cam requires a thrust button. McAfee will check cam endplay and adjust this against the COMP Cams two-piece timing cover before final assembly.
Before assembling all of the...
Before assembling all of the rods and pistons, McAfee mocked up one and bolted it on the crank to check piston-to-valve clearance with our Dart Pro-1 heads. Ours was a little tight on the exhaust side (McAfee likes to see .110-inch clearance at max lift on the exhaust and .050 on the intake unloaded), which left us the choice of fly cutting the pistons or retarding the camshaft 2 degrees. We determined that retarding the cam wouldn’t free up enough clearance, and for the best power, we decided to leave the camshaft timing alone and take a little material out of the intake pocket of the pistons.
The Mahle pistons call for...
The Mahle pistons call for 1.5/1.5/3.0mm rings. McAfee filed the rings to get consistent gaps of .018 for the top and .015 for the second rings. His advice for naturally aspirated motors is to follow the manufacturer’s recommended spec.
Using Dart assembly lube on...
Using Dart assembly lube on the friction surfaces of the bearings and ARP assembly lube on the rod-bolt threads, each rod and piston assembly was slid into place and torqued. The last spec that McAfee checks before turning the engine over again is rod side clearance, which on this engine was pretty consistent at .027 inch.
The final measurement of the...
The final measurement of the short-block is the deck height, or where the top of the piston sits in relation to the top of the block deck at top dead center. Our engine ranged from .026- to .027-inch deck height. Combined with a .034-inch head gasket (when compressed) and 64cc chamber heads, our 427 will net out at exactly 11.2:1 compression. With aluminum cylinder heads and a pretty radical cam profile, that will run on pump gas just fine.
If you order a Dart SHP short-block,...
If you order a Dart SHP short-block, this is what you can expect to receive in the mail, minus the camshaft and timing set. This is the start of a very serious small-block that looks like a 350, but will pound the ground like a big-block. Next month, we’ll bolt on the heads, the rest of the valvetrain and the intake, add fuel and spark, and see what this specific combo is worth on the dyno!