Richard Holdener
November 1, 2009
The two-barrel heads used on the 400M featured 79cc combustion chambers, which further lowered the static compression ratio on the stock motors. When combined with the dished pistons residing well down in the hole, the result was a less-than-optimum 8.4:1 compression.

One of the areas of concern with the tall-deck 400M is the intake manifold. Both the 351M and 400M motors were factory equipped with two-barrel intakes. There are a few different aftermarket manifolds available for the 400M, but both the Edelbrock Performer and Weiand Action Plus manifolds were designed for milder applications equipped with the factory two-barrel heads. Given the success in Engine Masters Challenge competitions with legendary builder John Kaase, the boys from CHI designed and cast a high-performance, single-plane intake designed specifically for use with their aluminum Cleveland heads on the tall-deck 400M.

Lucky for us, the port configuration on the intake was close enough to the Pro Comp heads to allow us minor port-matching to facilitate use of the CHI 400M intake on our test motor. The CHI 400M intake came to us on loan from the Cleveland experts at MPG heads in Englewood, Colorado (www.mpgheads.com).

Like all two-barrel heads, these featured the positive-stop, bolt down (non-adjustable) valve train for use with the hydraulic flat-tappet cams. We ran the stock two-barrel heads with the stock stamped-steel rockers (from Elgin).

MPG also supplied a set of adapter plates to facilitate use of standard 351 Cleveland intakes on the 400M. The spacer plates were necessary due to the deck-height difference between the 9.2-deck 351C and the 10.3-deck 400M. Its custom spacers allowed us to run an Edelbrock Performer RPM Air Gap (351C) intake on the 400M. These same spacer plates (if the ports were sized properly) would allow you to run any two-barrel or four-barrel manifold currently available for the 351C.

We turned to Holley for carburetion, in the form of a 750hp Street carb. The 750 Holley was further enhanced with Percy's Adjust-a-Jet system. The Adjust-a-Jet system allowed external jetting changes to the Holley, which made dyno testing even easier.

With the majority of the hard parts taken care of, it was time for the minor components. These included the ignition, exhaust and water pump. Ignition chores were handled by a Ford distributor (pulled from a 514 crate motor) along with a Pro Comp wire set. Though not required for this application, the Westech dyno was equipped with an MSD Digital 7 ignition amplifier.

Since the carb was missing when we sourced the motor from the wrecking yard, we simply installed a 500-cfm Holley two-barrel Westech had on hand.

Our exhaust needs were handled with a set of Hooker Super Comp headers. The 1 7/8-inch headers were designed for an early Mustang chassis and offered plenty of flow for the 400M application. The Hooker headers were run through 18-inch collector extensions, while Meziere supplied an electric water pump for our 351C/400M application.

Additional components included a 28-ounce balancer from Pro Comp, ARP 1/2-inch Cleveland head studs and Fel-Pro head and intake gaskets. Since the idea was to run the 400M in (near) stock trim, and then again after swapping over the heads, cam and intake, we required a few sets of gaskets to perform our make over. A set of Ford Racing finned-aluminum valve covers spiced up the freshly-painted 400M (Pro Comp also offers cast-aluminum Cleveland valve covers), while Lucas oil products (oil, break-in lubricant and octane booster) ensured our street motor had plenty of octane and lubrication. The stock cam was liberally coated with moly-based assembly lube and we added a container of high-zinc, break-in additive from Lucas Oil before pre-lubing the 400M using a drill motor on the oil pump driveshaft. Oil pressure from the drill motor was provided until we had oil present in every rocker arm.

The first order of business was to run the 400M in (near) stock trim. Changes to the factory Ford included the set of flat-top pistons (increasing the static compression ratio from as low as 8.4:1 to near 9.0:1). This was accomplished by combining the flat-tap pistons with an increase in bore diameter (4.00-4.030), decking the block and altering the compression height of the pistons. From the factory, the dished pistons were down in the hole nearly 0.060 (after 1971). This helped dramatically reduce static compression on the stock motors. Though we installed the flat-top Cleveland pistons from Probe Racing, they were still 0.060 down in the hole.