Imagine an aluminum head small block that makes 355 horsepower. What if it had a steel roller camshaft, four bolt main block, undercut rolled fillet crankshaft, high silicon pistons and strong PM connecting rods? We imagined it, and then engineered, developed, tested and built it. The ZZ4 is the evolution of our popular ZZ series of small blocks that power thousands of street rods, hot street cars, circle track racers and drag racers. With over 400 ft.lbs. of torque, the ZZ4 is the best way to put an aluminum head, roller cam, high performance small block between your favorite fenders. The aluminum angle plug cylinder heads have screw in rocker studs, 1.94" intake and 1.50" exhaust valves and 58cc combustion chambers that yield a crisp and responsive 10 to 1 compression ratio. Also included are our lightweight valve spring retainers that weigh half as much as our previous design. The valve seats are radiused and we’ve included valve stem seals to help keep the oil where it belongs. To compliment the cylinder head design, we’ve incorporated a steel roller tappet camshaft with .474" intake and .510" exhaust valve lift. The combination makes 355 horsepower at 5250 rpm and has that great sounding muscle car idle, with just enough lope to let people know that this is no station wagon engine. Also included with the ZZ4 is an HEI distributor with an ignition timing advance curve developed for performance, a dual plane aluminum intake manifold that accepts your spread bore or square bore carburetor, an 8" high-RPM torsional damper, 12.75" auto trans flex plate and cast iron water pump. The ZZ4 is currently our most popular crate engine, and you can see why. With a long history of successes in circle track and drag racing as well as street rods and other performance applications, the ZZ4 may just be the bullet for your next project. The ZZ4 is not intended for marine use, and should only be used in 1975 and earlier pre-emissions street vehicles or any year off road vehicles.