Modified Mustangs & FordsHow To Engine
351C Performance With Common Parts - A Cleveland Course of Action
A&S Motorsport Builds on 351C Performance with Common Parts
Ford's 351 Cleveland is legendary for the performance it has given us for 36 years. However, we admit to being confused by Ford's decision to manufacture the 351C . It already had the 351W, a raised-deck 289/302-based mill conceived to go after Chevrolet's 327 and 350ci small-blocks. The 351C was loosely based on the 289/302, with identical cylinder spacing, but it had a different oiling system and an Oldsmobile-like front timing cover, main bearing caps, and fuel pump configuration.
Although we have never been able to confirm this theory with Ford insiders, we're convinced Semon E. "Bunkie" Knudson had everything to do with the 351C's conception. Knudson was hired away from General Motors by Henry Ford II to run Ford Motor Company during the late '60s. When Knudson arrived in 1967, the 351W was already well underway and scheduled for production beginning in 1969. The 351C was introduced in 1970.
We base our Knudson 351C theory on design elements that it shares with notable GM V-8 engines. The same can be said for the 385-series Ford big-block (429/460 ci), which has design elements also borrowed from GM just about the time Knudson was running Ford. The Cleveland's oiling system, timing cover, and cylinder heads distinguish it from traditional Ford V-8s. The 351C's canted-valve (poly-angle) cylinder heads are obviously borrowed from big-block Chevys. Its oiling system, timing cover, and fuel pump configuration are clearly influenced by Oldsmobile-with the exception of the fuel pump's location on the opposite side. It is the only Ford V-8 ever produced with a 12/6-o'clock fuel pump bolt pattern like Oldsmobile's.
We will never know for sure, but you can bet Knudson's engineering people walked into Ford and speculated about what could be done with those stifling small-block Ford heads. The result would be the canted-valve, large-port Cleveland/Boss 302 cylinder head. What's more, they probably did the same thing with Ford's LeMans-winning FE-series big-block-replacing it with the 385-series 429/460 big-block later on. We will go out on a limb by saying each of these engine families survived, because it was undoubtedly a political battle between Knudson's GM outsiders and Ford's established engineering people.
When Ford introduced the 351C in 1970, it was embraced by enthusiasts for its large-port, poly-angle valve heads and its ability to produce lots of power. The aftermarket promptly went after performance buffs, setting them up with single- and dual-plane high-rise manifolds, tunnel rams, ignitions, hot cams, carburetors, and more. Big-time drag racers took the 351C and put it to work in 8-second Ford compacts, such as the Gapp & Roush "Tijuana Taxi" Maverick sedan. Saturday-night warriors did the same thing with Mustangs, Fairlanes, Torinos, and Cyclones, going after the competition with Ford's newest V-8. The 351C wound up being a phenomenal success during the '70s.
What helped the 351C also contributed to its demise in 1974. When Knudson was fired from Ford in 1970 and replaced by Lee Iacocca, we're convinced most support for the 351C went with him down the elevator to Michigan and Southfield. Of course, Ford didn't give up the 351C completely. It raised its deck to create the 400M for 1972, which replaced the FE-series 390/428ci big-block in passenger cars. In 1975, the 351C was dropped and replaced with a destroked 400M known as the 351M-both had big-block bellhousing bolt patterns.
We would like to hear your thoughts about the Knudson/351C connection. Can anyone answer us about the 351C's origins? We invite your feedback at Jim.Smart@sourceinterlink.com.
Getting 351C Performance
Ford's 351C is challenging because its cylinder heads were never practical for street use. This is a high-revving V-8 designed to do its best work on the racetrack, thanks to big-port heads, poly-angle valves, and wedge chambers. What makes it successful on the racetrack is what makes it a dog for street use because we need good low-end torque for the commute. Anyone building a Boss 302 understands this because Boss 302 engines were fitted with modified Cleveland heads. It was designed for high-revving Trans-Am racing, not fetching groceries. The same can be said for the 351C.
To meet the need for low-end torque, Ford's North American engineers opted for smaller intake and exhaust ports on the 351C-2V head along with open chambers to get compression down. The downside to this open chamber is its detonation tendencies. It tends to create two opposing flame fronts under mod-erate to heavy acceleration. The very thing it was intended not to do-ping-it does with great regularity. Smaller wedge chambers actually ping less than open chambers thanks to shape and quench area.
In Australia, Ford engineers improved the U.S. 351 Cleveland head with small 2V ports and tight 4V wedge chambers. Aussie Cleveland heads are the hot ticket for Clevelands with generous build budgets and access to these heads from Down Under
The 351 Cleveland has never been easy to build because the best parts are elusive. Because Ford produced this engine for just four short years, it has become harder and harder to find parts in recent years. What's more, Cleveland castings have long been plagued with failure issues (cracking). Some can be repaired, but a lot of them cannot.
We can dream of Aussie heads, which are expensive and hard to find. And we may also consider aftermarket aluminum heads for the Cleveland, but those don't come cheaply, either. So, lets go with what you can expect to find at a swap meet or in the classifieds for your 351C build. Our good friend John Douglas in Riverview, Florida, builds a lot of 351C engines annually. He knows how to build a streetable 351C that you can live with daily and make lots of power with on a Saturday night.
The 351C block offers unprecedented strength in two- and four-bolt main versions. Through many 351C buildups, we have learned that all versions of this block are virtually the same except for two- or four-bolt main caps. All two-bolt main blocks can be drilled and tapped for four-bolt main caps. Strength comes from heavy main webs wrapped around 2.749-inch main bearing journals. Ironically, the 351C has a smaller main bearing journal than the 351W, which is larger at 3.000 inches. Smaller mains yield less friction, which is likely the motivation behind the smaller main bearing size on the 351C.
Cleveland oiling systems from the factory fall short in terms of oil delivery to the main bearings, which bites a lot of us who build Clevelands. It's a good idea to begin Cleveland oiling system mods at the pump. Opt for a Speed-Pro high-volume pump, which yields 25 percent more volume thanks to a wider G-rotor package and cavity. It is also advisable to install a 100-psi pressure-relief spring if you're going racing. Ideally, you will blueprint your 351C oil pump before installation. MCE Engines in Los Angeles, California, can blueprint a Cleveland oil pump for you and ship it ready-to-install. The next oiling system mod is a restrictor kit from Moroso (PN 2205), which improves oil flow to the main bearings.
The good news with Cleveland engines is that they're hardy blocks that need a little help if you intend to go racing. For street use, they need minor modification. As we have learned from other engine builds, oil passages need to be worked smooth to reduce oil turbulence. The same is true for oil drainback holes, which need help to improve oil scavenging.
We suggest having any Cleveland block checked for cracks and thin cylinder walls before proceeding with machine work. Sonic checking cylinder walls helps find weaknesses before machine work. Magnafluxing the block and crank is also necessary prior to getting started. Work out stress risers and other rough spots to prevent weaknesses and failure. You can use a die grinder on any block to eliminate weaknesses. The objective here is to reduce or eliminate any chance of failure. Coating inside surfaces with GE's Glyptol, available from The Eastwood Company, improves oil-return flow and keeps stray iron particles where they belong.
Cleveland Vs. Windsor-What's In A Name?
How did 351ci engines get their names? When Ford came out with a second 351ci V-8 in 1970, Ford dealer technicians found themselves faced with a lot of confusion when it came to engine identification. It is virtually impossible to confuse the 351W with a 351C because they have completely different cylinder head and block architecture. In 1970, both were still so new that Ford needed to explain the differences and give each engine a family name. Ford's solution was to name each engine for the plant from which it was produced.
Raised-deck 351ci engines were named "Windsor" for their Canadian plant across the river from Detroit. Poly-angle-valve 351ci engines with wide valve covers were named "Cleveland" for their northeast Ohio roots.
These names stuck and have been used ever since. Some confusion abounds with Cleveland and Windsor because 221/255/260/289/302ci engines were also produced at the Cleveland Engine Plant. Their castings were produced at the Cleveland foundry. Added confusion abounds when we find 289/302 heads produced at the Windsor foundry. The rule of thumb is 221/255/260/289/302ci engines were Cleveland based, with all of them produced in Cleveland. The 351W engine was Windsor produced. By the same token, the 351C was Cleveland produced exclusively.
Whenever we call 221/260/289/302ci engines Windsor small-blocks, we're mistaken. None were ever produced in Windsor. Only the 351W was produced in Windsor, Ontario-along with a smattering of 289/302 small-block heads.
Cleveland heads were produced in several variations. Most common is the two-barrel (2V) casting with 74-77cc open chambers, 2.050-inch intake, and 1.659-inch exhaust valves. These are easily identified by their open "bowl" chambers and D0AE-E or DOAE-J casting numbers. This is a good street head because the port size is more conducive to the low- to midrange torque we want on the street. Aftermarket intake manifold availability is better with these heads as well. The 2V head was used not only on the '70-'74 351C, but the 351M and 400M engines as well, which explains availability.
Four basic types of 351C-4V heads were produced-closed chamber, open chamber, Boss 351, and High Output. Much of it has to do with compression ratio and mechanical lifter use.
Early 351C-4V engines were fitted with closed-chamber (61-64cc), large-port heads. This is an excellent high-revving street/strip head for those who want iron heads. In 1973-'74, Ford went with a 73-78cc open chamber in the 4V head, virtually identical to the 2V head. This head is easily identified by its large ports and 2V-style open chambers. It's the least desirable head available, but sometimes it's all you're going to find.
The '71 Boss 351 head is extremely hard to find, thanks to adjustable stud-mounted rocker arms and closed 64-67cc wedge chambers. The '72 High Output that came a year later has adjustable stud-mounted rockers like the Boss 351. But larger 73-76cc open chambers make it less desirable than the Boss 351 head. The truth is, aside from the stud-mounted rocker arms and large ports, the '72 High Output head isn't desirable outside of a restoration.
|Quick Reference Guide to 351C/351M/400M Heads|
|Engine and Years||Casting No.||Chamber Size||Valve Size, Int/Exh||Port Size|
|74-77 cc||2.04 in/1.67 in||2.02 in x 1.65 in, Int |
1.84 in x 1.38 in, Exh
|61-64 cc||2.19 in/1.71 in||2.50 in x 1.75 in, Int |
2.00 in x 1.74 in, Exh
|D3ZE-AA||73-76 cc||2.19 in/1.71 in||2.50 in x 1.75 in, Int |
2.00 in x 1.74 in, Exh
|D1ZE-B||64-67 cc||2.19 in/1.71 in||2.50 in x 1.75 in, Int |
2.00 in x 1.74 in, Exh
|D2ZE-A||73-76 cc||2.19 in/1.71 in||2.50 in x 1.75 in, Int |
2.00 in x 1.74 in, Exh