Formula For Success
Engine building isn't always just about engine building; it's also about choosing the right parts. Building a healthy street Cleveland involves choosing the right heads and induction system, which is key with the 351C. Choose a single-plane manifold and 4V heads with a 351-inch bottom end, and you can forget low-end torque. A single-plane manifold with 4V heads makes its power at high rpm. And that means peak torque around 6,000 rpm, not at 3,500 rpm where you need it most on the street.
The 351C-2V head is more appropriate for street use because it has smaller ports and valves, which moves peak torque down where we need it most: at 3,500 rpm. Choosing the right camshaft profile and dual-plane intake manifold improves driveability tenfold. Torque comes on crispy and strong as the engine spins through 2,500-4,000 rpm. The downside to the common U.S.-built 351C-2V head is its wide-mouth open chamber. You get good quench with this chamber, but lousy dynamics because it tends to create two flame fronts under hard acceleration, which causes spark knock (pinging).
The best Cleveland head on the planet is the Australian 351C, with the best combination of ports and chambers: the 351-4V wedge chamber and the 351C-2V ports for better low and midrange torque. PowerHeads is your source for the Aussie Cleveland heads, which are supplied ported and fitted with hardened exhaust valve seats. It's the perfect Cleveland street head.
Speed-O-Motive builds its 351C much the same way it does small-block 289/302s. Oil galleries get a workout where necessary. Oil return flow is improved to ensure sufficient oil in the pan. Press-in oil gallery plugs are tossed in favor of screw-in plugs.
 Screw-in oil gallery plugs...  Screw-in oil gallery plugs are installed in front of the block for improved oiling system security. |  Because Speed-O-Motive hones...  Because Speed-O-Motive hones the main saddles, main bearing security is improved. We're running a nodular-iron crank, so we're using regular street bearings. Use race bearings only with a steel crank. |  Rear main seals tend to be...  Rear main seals tend to be chronic leakers with small-block Fords, but it doesn't have to be that way. First, make sure the rope-seal retainer pin is removed. |
 Line the seal grooves with...  Line the seal grooves with a good silicone sealer and seat the rear-main seal halves. Then, stagger the seal gaps away from the main-cap gaps to reduce the risk of leakage. Use sealer between the cap and block. |  We like the way Speed-O-Motive...  We like the way Speed-O-Motive massages its crankshafts, with nice chamfer work at the oil openings and nice radius work at the journals. |  Speed-O-Motive checks bearing...  Speed-O-Motive checks bearing clearances two ways: by measuring the journals and bearings... |
 ...then using Plastigage to...  ...then using Plastigage to confirm the measurements. In this case, we have .002 inch of clearance. |  Before Speed-O-Motive installs...  Before Speed-O-Motive installs the crank, it applies sealer between the seal and groove, and between the main cap and block. Engine assembly lube goes on the main bearings to ensure good lubrication on startup. |  We're running a flat-tappet...  We're running a flat-tappet hydraulic camshaft in this application, which gets us 414 hp and 446 lb-ft of torque. A roller cam with Aussie heads would get us closer to 500 hp and in excess of 500 lb-ft of torque. |
 Piston-ring end gaps are important...  Piston-ring end gaps are important to power. If you run the gap too close, there will be too much friction when things get hot. If you run it too loose, you wind up with blow-by. You need an optimum balance between a tight end gap and a loose one to use as much of the thermal energy as possible without creating too much friction. Check with your ring manufacturer because each is different. |  The common belief is that...  The common belief is that the two top rings are compression rings, but this is only half true. The top ring is a true compression ring for cylinder sealing, and the second is a compression ring and an oil-control ring designed to keep oil out of the combustion chamber. Note the dished forged pistons to control compression. Because we've added a stroke to the 351C's bores, compression is increased. Dishing the pistons gets it back where it belongs at around 10.5:1. |  Did you know the oil rings...  Did you know the oil rings are there to carry oil down the cylinder wall? Bench-racing logic has it backwards. Most believe the oil rings carry oil up the cylinder wall. Oil rings simply control oil patterns between the piston and cylinder wall. |