Special High Performance Chevy Block - Progression In A Recession

Dart Delivers Some Much-Needed Relief To Your Wallet In The Form Of Its New Shp 525HP Block.

Michael Galimi Sep 1, 2009 0 Comment(s)
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Dart offers a wide variety of combinations using its SHP engine block, including short-block and long-block assemblies.

The small-block Chevy is without a doubt the most popular engine in the world. Over the years, we have seen some wild variations come from these. Amazingly, the evolution continues some 55 years after it was introduced, with better cylinder heads, intake manifolds, engine blocks, and everything in between still arriving on a regular basis. These newly-designed parts have enabled our beloved Mouse to make ridiculous horsepower and live successful lives both on the street and the track, with up to 2,000 horses in forced induction combinations.

While those numbers certainly impress even the most hard-core folks, the price of glory typically comes with a big price tag. For enthusiasts that have a more restrictive budget, the aftermarket has plenty of affordable heads and intake manifolds to build a variety of powerful combinations. The catch has always been the stock block, of which GM produced millions over the years. One of these would have to be used in order to keep the buildup at a reasonable cost. The Gen I 350 blocks are still plentiful, thanks to the millions produced, but the supply of the larger 400ci Gen I small-block is depleting at a rapid pace.

Dart Machinery is staying ahead of the curve and released its Special High-Performance (SHP) Chevy block last year. It's aimed towards the more affordable side of the hobby, but without compromising quality. This new block is a high quality product that eliminates days at a junkyard searching for a suitable block. The SHP block is a lower-cost solution to enthusiasts who want to build a healthy street-machine without breaking the bank. It allows them to start with a brand-new chunk of iron for the foundation of their high performance engines.

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The 400ci SHP engine with 9.5:1 compression, mild hydraulic roller camshaft, and 650 carb produced an impressive 525hp at 5,800 rpm. Technicaly, it's 400.9 cubes.

Dart might have kept the cost down, but its latest still includes a lot of great features not available in stock blocks. The company claims the SHP block can handle up to 600 hp, but we have heard stories of power levels just north of there in the 700 range, without any problems. The SHP block is available by itself, but Dart also offers complete top-end kits to complement it. Of course, one of its dealers can design a turn-key engine using all of Dart's components if one chooses that route.

Some of the highlights of the SHP block include a priority-main oiling system, Siamese bores (4.000 or 4.125-inch bores), 350 main journals (so it accepts commonly-available cranks), splayed four-bolt main caps (center three caps), a two-piece rear main seal, and provisions for OE roller lifters and cams. It uses the '81-85 stock-style oil pan and dipstick, as well as all bolt holes for accessories like starter and clutch ball.

Dart engineers reworked the cooling system for a more efficient design as well. The engine block can handle a roller-style valvetrain, but that doesn't prevent the use of flat-tappet cams if that is what you have on the shelf in your garage. Both style camshafts fit easily and nicely. The face of the block includes the hydraulic roller cam retainer plate bosses, but Dart designed the block so a standard timing chain cover would still fit. The SHP offers the best of both worlds in the valvetrain department, no matter your budget or intended use.

Hot on the heels of the SHP engine block release is a new line of assembled short-blocks offered directly through Dart's dealers. The company is probably more known for its in-house Pro Stock engine building program, but Dart does build short-blocks and long-blocks for retail (street) purposes. In fact, the same in-house department that builds the Pro Stock engines handles the SHP line-its credentials include three NHRA Pro Stock championships and over 60 national event wins. All this is under the watchful eye and direction of Dart's founder, Richard Maskin, a veteran Pro Stock racer and storied engine builder.

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Dart coated the top of the piston and the side skirts for an additional cost ($232 and $148, respectively). This process is done in-house and the company can coat any part-engine or otherwise.

This month, we peak inside an SHP short-block and then add a Dart top-end kit to see what kind of power the potent small-block could make on the engine dyno. The short-block was upgraded with a few options, including the larger 4.125-inch bore and piston coatings. Dart utilizes a 3.750-inch crank and when combined with the aforementioned bore size, the engine yields 400 cubes. The crank was upgraded to a forged 4340 steel unit. The base crank is a cast-steel piece. The rods in this test engine are the optional forged H-beam rods, and they swing upgraded forged pistons. Dart's standard SHP short-block and high-performance engines come standard with 4.000-inch bores and a 3.750-inch cast-steel crank for 377ci of fury.

Moving to the top of the engine, Dart had a custom grind camshaft for this application, but kept the hydraulic roller stick on the mild side. The lobes lift open the valves to a maximum of 0.540-inch on both the intake and exhaust side. Duration is listed as 236/242 at 0.050-inch lift. Due to the street nature of this engine, the shop decided to keep the idle smooth and even-a 110-degree lobe separation angle was used to accomplish that task. A popular cam for the SHP combination has been a hydraulic roller stick with 0.480/0.480-inch lift and 230/230 at 0.050-inch specs. This cam will produce about 20 less horsepower than the larger stick in the engine featured here.

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The coated forged piston is dropped into the hole using an installation ring. The install ring has a tapered opening and allows the piston rings to be compressed and slid into the bore easily.

The hydraulic roller cam opens and closes 2.02/1.60 valves in Dart Pro1 180cc heads. "The 180 head makes the best power on this engine package. We tried the 200 and 215, but the cam is little. The 180s work much better," commented Tony McAfee, engine builder at Dart. The intake manifold is a dual-plane Dart unit and the team used a Demon 650 for dyno testing. A 1/2-inch spacer under the carb produced the best results on the engine.

Dyno testing of this simple combination resulted in an impressive 525hp and 524 lb-ft of torque. It's a great alternative for the person who wants big power and doesn't want to go through the trouble and expense of using LS-engine.

Recession or no recession-horsepower will always be cool.

DART SHP Build Prices & Options
Note: These prices are full retail, so typicalstreet prices may be a bit lower.SHP block - $1,532
372 CI short block - $2,975
400 CI short block - $3,395
Upgrade/Forged crank +$600
Upgrade/Forged pistons +$425
Upgrade/H-beam rods +$275
Coating/Thermal barrier piston tops +$232 (set of 8)
Coating/Anti-friction piston skirts +$148 (set of 8)
Top end kit - Pro1 aluminum heads, dual plane manifold,chrome valve covers- $1,895

Dyno Graph
Engine: Dart SHP
Size: 400.9ci (4.125x3.750)
Compression: 9.5:1
Carburetor: Demon 650 with1/2-inch spacer

The assembled short-block awaits its top end. This is what you get when you order a SHP short-block. This is a great option for those who have a top end and need a new short-block. Dart uses all new parts and offers a variety of options.

Fel-Pro gaskets are used to seal the Dart Pro1 180 heads to the deck surface.

Dart has tested numerous heads on this type of short-block. Thanks to the mild cam and compression, the 180cc heads make the most power. The heads are aluminum and feature 2.02/1.60 valves.

The intake ports flow 257cfm at 0.500-inch lift, which are out-of-the-box results.

The exhaust port comes out-of-the-box to this party at a healthy 172cfm, also at 0.500-inch lift.

Dart's Jeff Lake highly recommends CMD extreme pressure lube. Here he is applying it to the ARP head bolts.

Lake torques the heads down as the engine nears completion.

A set of 1.5:1 roller rocker arms was bolted down after the pushrods were slid into place.

A Dart dual-plane intake was selected for this engine. Its design promotes low-end torque.

A Mallory distributor is in charge of the spark for this engine.

A Demon 650 carburetor was used on top of the 400ci engine and it worked flawlessly. The only upgrade was a 1/2-inch spacer that was installed during dyno testing.

A set of Dart chrome valve covers are added and the SHP engine is almost ready for dyno testing. At this point, some observant readers might notice the lack of intake bolts. Lake and McAfee bolted the intake down after these photos were taken.

The result is 525hp and a peak torque output of 524 lb-ft. It is a healthy street engine that won't break the bank and keep you ahead of those pesky Mustangs and late-model LS cars.

Sources

Dart Machinery
Troy, MI 48084
248-362-1188
www.dartheads.com
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