We don't doubt the toughness of the short-block; Musi told us of several 555s in service that inhale nitrous on a regular basis. Musi tested an earlier version of this engine with an Edelbrock Performer RPM nitrous plate (110 jet) and blasted the 555 to 1,018 hp and a max torque output of 1,140 lb-ft. He was happy to report that the customer still runs the engine after two years of abuse. Musi was also working on a prototype Edelbrock throttle body during our visit. He started with Edelbrock's four-barrel-style universal throttle body and is adding a nitrous port in the center. The nozzle will spray down into the manifold and will be run as a dry-shot of nitrous. That means only nitrous will be sprayed through the system, and the EFI will add the additional fuel required. It will offer a clean look while packing a massive punch-up to 400 hp Musi says.

"We went with a triple nickel because the bigger bore helps the head breathe better. That bore also allows a guy to go with a bigger one if he wears out the engine. The 555 is a really nice combo," Musi says. There is nothing like a joint venture to bring two powerhouses together to deliver a powerful and reliable product.

BY THE NUMBERS
EDELBROCK/PAT MUSI PERFORMANCE
555CI RPM XT CRATE ENGINE
Engine type: big-block Chevy
Displacement: 555 ci
Bore: 4.560 inches
Stroke: 4.250 inches
Block: Dart Big M 9.8-inch deck iron
Crankshaft: Scat 4340 steel
Connecting rods: Scat 4340 steel
Pistons: Mahle forged
Camshaft type: Edelbrock Rolling Thunder
Performer RPM hydraulic roller
Valve lift: .632-inch intake, .648-inch exhaust
Camshaft duration: 248 intake/256 exhaust,
at .050-inch lift
Cylinder heads: Edelbrock Performer RPM XT
(PN 51559), CNC-ported
Intake valve diameter: 2.300 inches
Exhaust valve diameter: 1.880 inches
Compression ratio: 10:1
Rocker arm ratio: 1.7:1
Intake manifold: Edelbrock Victor Jr.
454-R (PN 2902)
Recommended fuel: pump gas
with minimum of 91 octane
Max horsepower: 677 at 5,800 rpm
Max torque: 649 lb-ft at 4,800 rpm
Total cost, as-tested: $12,800 (carb)
$16,500 (EFI)