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Big-Block Chevy Engine Build - Project American Heroes: Shock & Awe

Project American Heroes Will Blow Away The Competition Thanks To Its 717-Horse Smeding Performance 572 Big-Block

By: Joe Rode, Mike Harrington, Photography by Mike Harrington

Smeding spends the extra time to internally balance all of their big-block Chevy assemblies. This makes it possible for the end user to easily adapt the correct flywheel and balancers.

The crankshaft is a 4.250-inch stroke, 4340 forged steel unit that is nitrated and internally balanced. The lightening holes in the journal are drilled before the crank is heat-treated so that no part of the crank goes untouched. Smeing uses only 270 degree rod and main bearings for optimum lubrication.

The 4340 forged H-beam connecting rods are 6.535-inch long, and incorporate ARP 7/16 cap bolts along with forged Ross Pistons with Total Seal moly rings.

Racing Head Service (RHS) Pro Action #11002 aluminum cylinder heads come with 2.300-inch intake and 1.880-inch exhaust valves. Intake port volume is 360cc, exhaust ports, which are raised .500-inch, have a volume of 135cc. Smeding reshaped the combustion chambers, outwardly opening them up to take full advantage of the monster 4.630 cylinder bore. Once the grinding was done, the heads were milled .025-inch, bringing the chambers back down to a pump gas-friendly 9.9:1 compression ratio. The combustion chambers are now 118cc (just slightly lower then the advertised 119cc size from RHS). While the heads came pre-assembled, Smeding, like any engine builder worth his dyno numbers, completely disassembled the check spring heights and pressures. Smeding set the spring pressures on the Comp beehive springs to their preferred closed seat pressure of 125 pounds, and opened seat pressure (at .600-inch of lift) of 340 pounds.

With all the machine work completed, the crank balanced, pistons and rods weighed and assembled...

...the short-block assembly went together without a hitch. And we were nearly ready for the top end build.

Smeding chose a Comp Cams hydraulic roller stick, ground to Smeding's specs of .613-inch lift (on both intake and exhaust), duration at .050-inch for intake of 248 degrees and 258 degrees for exhaust. Smeding orders its cams for a late-model engine, so they come with a stepped nose. This allows for the easy use of a thrust plate; no need to mess with thrust buttons to stop camshaft walk.

Comp's extra-large, heavy duty adjustable single roller timing chain assembly was used.

By Joe Rode, Mike Harrington
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