434 Power Upgrades - Power Added

Big-inch small-block with a side order of go juice

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Making power is easy. It’s only a matter of understanding what you want and how far you’re willing to take it.

1207chp 01 O  434 Engine Power Upgrades Dyno 2/14

If you recall, back in the Mar. ’12 issue (“The Bigger Mouse”), we ordered a complete Dart 434ci SHP short-block stuffed with all forged internals, had 10.3:1 compression, and a COMP hydraulic roller camshaft. Up top, we completed the package with a set of Dart CNC 227 cylinder heads and fed the fire with a Holley Ultra HP 750 carburetor.

When Westech Performance Group’s SuperFlow 902 put our mill to the test, the end result was 542 hp/552 lb-ft on pump gas. Again, our intentions were to build a real-world street mill that could idle, be driven anywhere, and have big-block–like torque, with a healthy rumble.

Since then, we’ve decided to maintain the core of the combination and only port-matched the intake manifold (“Max Flow,” Jun. ’12, pg. 20). For the second round, we wanted to see what this gem would produce with a mild hit of nitrous; our system of choice was a Nitrous Oxide System Cheater kit, which is good for an additional 100-250 hp.

1207chp 02 O  434 Engine Power Upgrades Carburetor 3/14

Also, at the recommendation of Westech’s Steve Brulé, we swapped out the original Holley Ultra 750 HP for a 950 version. While the 750 worked well, Brulé felt the 434 would benefit from the larger carburetor. All said and done, between the port matching and the 950 hp, our baseline numbers improved 13 hp and 6 lb-ft to 555 hp/558 lb-ft.

The naturally aspirated numbers are impressive, but wait until you take a look at the nitrous results. Where do we go from here? Time will tell, but we think you’ll like what we have planned. Until then, read on to see how to transform a mild street combination into a track terror on command.

434 Buildsheet

Displacement 434
Bore x Stroke 4.155 x 4.000 inches
Compression 10.3:1
Rod center-to-center 6.00 inches
Piston deck height 0.000
Chamber volume 66 cc
Rod bearing clearance 0.0025 inch
Crank endplay 0.007 inch
Main bearing cap torque 1-5 / 7/16 bolts / 65 ft-lb (moly-lube)
2, 3, 4 / 3/8 bolts / 35 ft-lb (moly-lube)
Rod bolt torque 70 ft-lb (moly-lube)
Head bolt torque 80 ft-lb (moly-lube)

1207chp 08 434 Engine Power Upgrades Side View 10/14

At a glance

1. Dart SHP block with a 4.155-inch bore // 2. Dart single-plane manifold/Nitrous Oxide Systems Competition Cheater Plate System (PN 02010NOS) // 3. 13/4-inch headers with 18-inch extensions and mufflers // 4. Dart CNC 227 cylinder heads // 5. Holley Ultra HP 950-cfm carburetor (PN 0-80805HB) // 6. Eddie Motorsports custom-engraved valve covers

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