OK, we admit it. We haven't been giving the 351 Cleveland enough ink lately. Seems everyone is building the venerable 289/302/351W small-block, which our readers love because they're plentiful and easy to build. That makes it easy for us--perhaps a little too easy.
Ford's legendary 351C middle-block was a back-door surprise for 1970. In 1969, Ford introduced the raised-deck 351 small-block we came to know as the Windsor. It looked similar to the 289/302, but it was a pinch wider, a hair taller, long on torque, and ready to make unrealized power. Then, scarcely a year into production, the 351W had company: the more powerful close cousin with the same displacement in the form of the 351 Cleveland. It's often been asked, why the same displacement from a different engine family? There have been a lot of theories, but so far no concrete answers from anyone who was there to see it unfold firsthand. We'll kick around some solid theories later in this article.
The 351W was little more than a raised-deck 289/302ci V-8 with the same 4.000-inch bore, but half an inch more stroke than the 302. It also had similar cylinder-head castings with slightly larger valves and ports. The 351C's 4.000-inch bore and a 3.50-inch stroke was dimensionally the same as the 351W, but it differed in block design and large-port, poly-angle-valve heads. The large-port heads were designed to flow better at high rpm, allowing the 351 middle-block to make extraordinary horsepower and torque on the racetrack. On the street, the 351C wasn't the powerhouse it was on the track because the oversized ports didn't yield the velocity at low rpm necessary to make good torque. This was certainly true with the 351C-4V and Boss 351 engines. In 351C-2V applications, low-end torque was improved, thanks to smaller valves and ports. But the 2V heads suffered from combustion-chamber shortcomings that caused excessive spark knock and reduced compression.
When building a 351C, it's a good idea to know how to amass the right parts to make the most of your buildup. We're going to show you how to coax more horsepower and torque from a 351C without having to sell the farm.
Crate engines from Speed-O-Motive...
Crate engines from Speed-O-Motive make the going easier. Here's a 408C stroker crate short-block ready for shipment. Speed-O-Motive delivers your crate engine in a nice container like this for solid protection.
This is Speed-O-Motive's 408C...
This is Speed-O-Motive's 408C stroker kit for the 351C engine with a 4.000-inch stroke, 6.000-inch Chevrolet rods, forged dished pistons, and a custom nodular iron crank--all precision balanced for assembly.
When we witnessed this build...
When we witnessed this build at Speed-O-Motive, the customer's budget was limited, so this engine didn't reach its potential. The buyer opted for an aggressive flat-tappet Comp Cams 260H High Energy flat-tappet camshaft, but we're convinced more power could have been had from a roller hydraulic camshaft, which is more expensive.
Three basic castings are available...
Three basic castings are available for the 351C: the 4V head shown, the 2V head (not shown) with smaller ports and valves with open chambers, and the more desirable Australian Cleveland head that offers the best of all worlds.
The Aussie head has the closed...
The Aussie head has the closed wedge chambers (4V head) with the smaller ports and valves (2V head) for improved torque. The 4V head shown performs much better when you're huffing 408 ci through those ports for improved low and midrange torque. You're also getting the mechanical advantage of a 4.000-inch stroke and the dwell time from longer 6.000-inch Chevy rods.
Our platform is a '70-vintage...
Our platform is a '70-vintage 351C casting (D0AE) that has been bored .030 inch. The main saddles have been checked and line-honed to keep the bearings secure. As you can see, the bores have been notched to clear the 408 stroker rod bolts. Oiling system mods are simple: one restrictor between the No. 1 main journal and the No. 1 cam bearing. This reduces flow to the cam bearings and increases flow to the mains where it's needed most.