Dart Short-Block Crate Motor - Halfway There
Dart's SHP Short-Block Crate Motor Has You Well On Your Way.
From the December, 2009 issue of Popular Hot Rodding
By Steve Dulcich
Photography by Johnny Hunkins, Steve Dulcich
Dart's SHP short-block helps...
Dart's SHP short-block helps you take several big steps forward on the way to a high-performance engine build. We ordered one up in a 400ci version, with all the goodies needed to make reliable power.
Just about any engine builder, whether a pro or a backyard hobbyist, looks at the completion of the short-block as a milestone in a performance engine build. Getting to this point in the process generally means that the grunt work is done, and the build shifts to dressing out the rest of the engine with a selection of high-performance parts. Getting over the hurdle of a completed short-block is almost always time consuming and sometimes frustrating. You might start by finding a good core, and unless you own a machine shop, the search will begin for a competent machinist who can do the work on time and at a fair price. All of the internal rotating assembly components must be reconditioned or sourced new, with everything sized and compatible with the rest of the parts going into the bottom end. With plenty of running around, phone time, and good planning, at the end you will have everything machined, balanced, and ready to assemble.
Short-block assemblies are nothing new, in fact remanufactured short-blocks have been around as a time-saver in the service industry for decades. The advantages are clear, offering a shortcut at getting the job done, which always pays when time is money. Dart has taken the concept to a new level with the Sportsman High Performance (SHP) short-block assemblies. Far from a re-man, this is a custom high-performance short-block built with all new parts, using Dart's excellent SHP cylinder block casting as the foundation. Instead of decades-old production-based pig iron, the Dart block is designed from the get-go as a high-performance unit, providing a level of beef you just won't get no matter what mix of time, effort, and parts you put in a stock block.
The Dart SHP short-block is...
The Dart SHP short-block is based on Dart's new SHP block casting. This block takes some of the best features of production GM blocks, but everything is upgraded for strength and performance. The valley area reveals that the block is set up to take the production-style hydraulic roller arrangement, meaning a hydraulic roller cam can be used without having to go to a more expensive retrofit-style lifter.
Dart has long been in the business of producing high-performance race engine blocks, both in cast iron and aluminum. The SHP block builds on that experience, by taking some of the best features of the race blocks, and casting them right into a block designed specifically for high-performance street and strip applications. You'll find features like revised oil system galleries to provide priority-main oiling, giving the critical main bearings a dedicated front-line oil supply. The block has metal in all the right places, with filled pan rails, stout main webbing, and siamesed cylinder walls that are more than thick enough to take the punishment. The block has revised water jackets for improved cooling, with the outer block wall scalloped to provide greater coolant circulation around the cylinders. Race engine-style four-bolt splayed main caps secure the crank with far greater integrity than any production block arrangement. Inside, the crankcase casting comes clearanced for a 3.750-inch stroke, saving the cost or effort of custom relieving a stock block for stroker crank clearance.
The block is set up with features to allow for the most popular engine configurations, with the lifter bosses and valley designed to accept a factory-style hydraulic roller camshaft and spider assembly. The front of the block has provisions for a camshaft thrust plate as used in late-model OEM Chevy small-blocks, eliminating the need for a thrust button in roller cam applications using the late model-style small-nose cam core. The block is configured with standard Chevy starter provisions, motor mounts, oil filter boss, and clutch pivot bosses for manual trans applications. The OEM-style fuel pump boss it there for a mechanical fuel pump, and the block maintains the traditional two-piece early-style crank seal.
Making The Short
Up front, Dart's SHP block...
Up front, Dart's SHP block comes with provisions for a thrust plate, as used in late-model Chevy small-blocks. This allows a small-nose cam to be used and eliminates messing with finicky thrust buttons.
With a block like the SHP, Dart definitely has the goods, and the bare block is available fully precision machined and ready for assembly. Taking the SHP concept one step further are the short-block assemblies from Dart. Here you have the SHP block already filled with a balanced high-performance rotating assembly, ready to go. There are several options on just how to have your short-block built, with assemblies available at a 4.125x3.480-inch bore and stroke for a 372ci version, or the 400-cube version at 4.125x3.75 inches. The basic assemblies come standard with a cast steel crank, I-beam rods, and hypereutectic pistons. From there, upgrade options can step up the basic short-block with forged pistons, H-beam rods, and a forged crank, at extra cost. With the SHP program, you can order your short-block with the options deemed necessary to meet your requirements, and rest assured that with Dart's name on the crate, the assembly is built with the quality parts and machining needed to go the distance.
We liked the idea of taking the fast track to a high-performance street engine, and ordered up a 400-cube SHP short-block upgraded to the fully forged internals ($4,695). We had the engine shipped to Andy Mitchell's Outlaw Racing where we thoroughly scrutinized what the package has to offer. Our plans in the next month or two (deadlines permitting) are to use the SHP crate to build a solid street performer, one that makes the number in a reliable and driveable combination, but has the added beef to utilize a moderate shot of nitrous without having to worry. With the Dart short-block, our engine build was halfway done by the time we opened the box!
Flavors Of SHP
Dart offers several versions of the Sportsman High Performance short-block crate engine. Not only can you choose your pistons (hypereutectic or forged), but you have a choice of connecting rods (I-beam or stronger H-beam forgings), and crankshafts (cast steel or forged 4340). That's a level of choice that's unheard of for a crate motor; think of it as getting a custom handbuilt short-block at a bargain price. The price range listed here would be for hypereutectic pistons, I-beam rod, and a cast crank at the low end of the scale, to a forged piston, H-beam rod, and a forged crank at the top end of the range. (All small-block Fords come with forged pistons.) Keep in mind that you can mix and match if you want, so it's possible to get, as an example, a 454 big-block Chevy with a forged piston, H-beam rods, and a cast crank if you so desire.
|Small-block Chevy, 372 ci
||$2,975 - $4,275
|Small-block Chevy, 400 ci
||$3,395 - $4,695
|Big-block Chevy, 454 ci
||$4,246 - $5,546
|Small-block Ford, 347 ci
||$3,475 - $4,350
|Small-block Ford, 363 ci
||$3,939 - $4,814
Besides the greatly enhanced...
Besides the greatly enhanced strength, you'll find the SHP block has all of the provisions required for most typical street applications, such as a functional and fully machined fuel pump boss for a mechanical fuel pump.
A feature we really like is...
A feature we really like is the fact that the engine is balanced as a neutral assembly, so the offset-balanced dampers and flywheels are not required. Not only is this arrangement better from a mechanical balance standpoint, but it simplifies the engine installation.
We found the piston's deck...
We found the piston's deck to be at -.030 inch with the flat-top pistons, which will provide a compression ratio in the 10:1 range with a set of 72cc heads, or 11:1 with 64cc heads. We plan on assembling our long-block with Dart's Pro 1 64cc head (200cc runner volume), which will put us right at the limit for pump gas.
The Dart SHP block comes with...
The Dart SHP block comes with siamesed cylinder walls with cylinder bore thickness you can only dream of with a stock block. Dart claims a minimum of .230-inch wall thickness at a 4.165-inch bore size (+.040). This cutaway cross section of the block illustrates the extra meat.
Unlike a production block,...
Unlike a production block, the SHP block is plumbed for priority main oiling, which means the main bearings receive oil before the less critically loaded cam bearings. This cutaway shows the main gallery (right) and the oil pathway down to the mains and back up to the cam.
To aid cooling, the block's...
To aid cooling, the block's water jackets are ballooned around the cylinder walls (cylinder bulge), adding critical capacity where it is needed most on a big-bore small-block. Note the OEM-style motor mounting bosses, and the clutch pivot bolt bosses included on the block.
Downstairs, you'll find splayed...
Downstairs, you'll find splayed four-bolt ductile-iron main caps, and a much more rigid block structure. The block comes with a production-style oil filter boss and a right-side dipstick location.
At the rear cap, we see that...
At the rear cap, we see that the block is configured for a two-piece rear main seal arrangement, making the block compatible with the more commonly available early style crankshafts. Oil pump mounting on the rear cap is conventional Chevy.
Standard on the short-block...
Standard on the short-block assemblies is a set of forged I-beam rods with 3/8-inch capscrews. Our short-block was upgraded to H-beam rods, which feature 7/16-inch fasteners.
Mounted to our rods are a...
Mounted to our rods are a set of Mahle forged pistons, another upgrade. The pistons feature a coated crown and skirts, and of course, the pins are floating.
The upgraded ring package...
The upgraded ring package that complements our pistons are Hastings in a 1.5/1.5/3mm moly top package. The relatively thin ring cross section reduces drag, and improves power output.
The modern skirt design of...
The modern skirt design of the Mahle piston results in a stable and strong internal geometry, and a much reduced piston pin length. The short pin reduces the reciprocating weight considerably.
Since the SHP block is designed...
Since the SHP block is designed from the start for high performance, the block is cast with clearance for up to 3.750-inch strokes using steel rods, without requiring additional grinding.
One thing we will really appreciate...
One thing we will really appreciate when the time comes to bolt the Dart top-end kit to our SHP short-block assembly is the blind cylinder head fastener holes in the decks. Production blocks go into the water jacket here, requiring sealant. With the blind holes, this potential seepage path is eliminated.
We'll be bolting the whole...
We'll be bolting the whole thing together using a Dart top-end kit ($1,849) consisting of Pro 1 cylinder heads (200cc runners, 64cc chambers, 2.02/160-inch valves) and Dart's dual-plane air-gap-style intake. The Dart top-end kit comes with assembled heads, intake, fasteners, gaskets, spark plugs, and valve covers. You can build up your SHP short-block (or any other short-block) on a budget with Dart's formula; kits start at $1,639 for Iron Eagle heads, and go up to $3,378 for CNC-ported Pro 1 aluminum heads and a single-plane intake.