Ford small-block V-8s have always had a difficult time making power because they’ve always been limited by factory cylinder head port design issues. Small-block Ford intake and exhaust ports are too restrictive. By contrast, the 351C/351M/400 intake ports are too large with restrictive exhaust ports. Ports that are too large can reduce power as much as ports that are too small. When ports are too large, they limit low- to mid-range torque, which isn’t worth much on the street where these engines live. When you consider poor exhaust scavenging, it adds insult to injury.
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If you’re using stock cylinder heads, selection is limited but you do have some options. A good cylinder head porting shop can do a lot with 351W heads if you want to gain power from your 289/302. You can run the 351W head without port work or you can invest time and money in port work.
Another consideration in choosing the right 351W cylinder head is combustion chamber size. The 351W cylinder head received the same dimensions (port and valve size) as the 302 head in 1978. When you’re shopping for 351W cylinder heads, aim for 1969–1973 castings, which are the best heads for the 289/302.
From an economic standpoint, aftermarket cylinder heads remain the best value because selection is great and you can buy them and bolt them on without waiting for port work. And because most aftermarket heads are aluminum, you can opt for higher compression without the risk of detonation because aluminum heads are much better heat conductors.
Small-block Ford cylinder head identification is easy if you take the time to understand Ford castings. The most important clues are casting numbers and date codes. You also need to understand the difference between a casting number and part number; they are rarely the same. Begin with the Ford casting number, then look for the date code.
221/260
The 1962–1963 221-ci cylinder head is easily identified by its very small kidney bean–shaped 45- to 51-cc combustion chambers along with 1.590/1.390-inch intake/exhaust valves. These cylinder heads have casting numbers C2OE or C3OE and are virtually identical in appearance.
The 260 heads have larger 52- to 55-cc wedge chambers with the same valve 1.590/1.390-inch sizes. Expect to see C2OE-F and C3OE-B prior to February 1964.
In February 1964, Ford introduced an improved 260 head with larger 1.670/1.450-inch valves along with the same 52- to 55-cc chambers. The revised head is numbered C4OE-B and works on both the 221 and 260 without consequence.
289
The 289 cylinder head was produced in several casting types beginning in 1963. Like the 260 head, the 289 casting has small 52- to 55-cc chambers with a more recessed spark plug. Valve size remained the same as the revised 1964 260 head at 1.670/1.450-inch intake/exhaust.
In March 1964, Ford increased the 289’s intake valve size to 1.780 inches while keeping the exhaust valve size at 1.450 inches.
The 289 head casting numbers in 1963–1964 were C3AE-F, C3OE-E, C3OE-F, and C4AE-C. Casting numbers changed to C5DE-B, C6DE-G, C6OE-M, C6DE-C, and C6DE-E in 1965–1966. The C6DE-C and C6DE-E heads are Thermactor smog-reduction castings and not of much use unless you are performing a restoration on a Ford or Mercury originally so equipped. Thermactor emissions cylinder head exhaust ports, which are very restrictive, can be hogged out for performance use, but there’s a lot of port work involved and usually costs more than it’s worth.
Before May 2, 1966, Ford machined pushrod guide holes into the 289 cylinder head castings. From May 2, 1966 forward, Ford found a more cost-effective way to manufacture 289 engines by eliminating a cylinder head machining step (narrow pushrod guide holes) and using rail-style rocker arms, which were designed to keep rocker arms centered on longer valvestems.
The earliest 221/260 combustion chambers were similar to this 289 wedge chamber (fitted with a hardened-steel exhaust valveseat) yet smaller at 45 to 51 cc and shaped more like a kidney bean yielding very low 8.4:1 compression for use with regular gasoline. Valve sizing for the 221 and 260 was 1.590/1.390 inches. In mid-1964, the 260 received larger 1.670/1.450-inch valves.
This is the 289/302 combustion chamber at 52 to 55 cc with 1.780/1.450-inch intake/exhaust valves. Early 289 engines (1963–1964) had 1.670/1.450-inch intake/exhaust valves like the 260. In mid-1964, 289 valve sizing was changed to 1.780/1.450 inches and remained until 289 production ended in 1968. Early 302s had virtually the same cylinder heads as the 289.
Cylinder head castings were typically marked like this. Early 221/260 cylinder heads weren’t always marked this way. Instead, they received casting numbers such as C2OE, C3OE, along with alphanumeric date codes.
This 289 cylinder head casting number is marked with “C5AE,” which means it’s a 1965 Ford casting. Else-where on this particular head is “289” and “65,” which further confirms identification. Also expect to see an alphanumeric date code.
Although rail-style rocker arms saved Ford money, they were never a good idea because they tended to jump off the valvestem at high RPM, which can be catastrophic. In fact, rail-style rocker arms are generally a bad idea because, as the rocker wears, the rails move closer to the retainer, putting the engine at risk for valve- spring retainer failure. The minute you hear rocker arm noise (clicking) with rail-style rockers, the rails are into the keeper and must be replaced.
Cylinder heads designed for rail- style rocker arms are numbered C7OE-A, C7OE-B, C7OE-C, C7OZ-B, and C7ZE-B from mid-1966 through 1967. Don’t be surprised to find a 1968 289/302 engine with these heads because there was considerable overlap.
For 1968, casting numbers to look for on a 289 are C8OE-D, C8OE-L, and C8OE-M, which have larger combustion chambers for reduced compression and improved emissions. Despite minor changes in chamber size and shape, these heads are virtually the same as previous castings except for the machined-in provisions on the exhaust side for the Thermactor air-injection pump system. The main thing you want to watch for is valve and combustion chamber sizing (larger chambers mean less compression). Another important difference for 1968 are positive-stop rocker arm studs, which are not adjustable. You only need to slowly run them down to the stop. Expect to see some overlap with adjustable rocker arm studs in 1968.
289 High Performance
The 289 High Performance cylinder head is a unique small-block casting with cast-in valvespring pockets and screw-in rocker arm studs, which are the only elements that made them different from a standard 289 cylinder head. These nuances help maintain valvetrain stability at high RPM, which makes them appealing for high-performance applications. However, you don’t need 289 High Performance cylinder heads to get high performance from your small-block. Your machine shop can install screw-in rocker arm studs, pushrod guide plates, and valvespring cups with the same result. Valve and port size is identical to 289-2V/4V heads at 1.780/1.450 inches.
The 1967 289 High Performance head has slightly larger ports with the same 1.780/1.450-inch valve sizing; the increased port size difference is insignificant to performance.
The best 289 High Performance cylinder head is the C3OE, which is the early 1963 casting with smaller 49.2-cc chambers for greater compression. This head also has smaller valves (1.670/1.450 inches), which hinder performance to some degree. This head is desirable because of its smaller chambers for great compression. However, it may be limited by smaller valves, which can be replaced with larger 1.940/1.600-inch valves to improve performance (Chevrolet valve sizes). Watch out for excessive valve shrouding when you use larger valves.
The 289 High Performance cylinder head is a unique casting because it has valvespring pockets and screw-in rocker arm studs for valvetrain stability. Intake and exhaust ports are the same as on the 289-2V/4V along with 1.780/1.450-inch intake/exhaust valves.
This 289 High Performance cylinder head has screw-in rocker arm studs, valves, retainers, keepers, and springs. Because these rocker arm studs screw into the water jacket, you must use a commercialgrade Teflon sealant to keep coolant where it belongs. (Permatex’s The Right Stuff is also an excellent sealer for stud threads.) If you install them without sealant you will have coolant leaks.
The “289” with two bumps is exclusive to the 289 High Performance cylinder head. External markings (cavity numbers 19, 20, 21) in the outside corners are also a quick means to Hi-Po head identification. If you see any of these numbers you have a 289 High Performance head.
The 289 High Performance cylinder head has the same intake ports size as its 2V/4V counterparts, which means it doesn’t breathe any more aggressively than the 2V/4V. An experienced cylinder head porting shop can perform wonders with a Hi-Po head without it being noticeable externally. Good port and bowl work reduces restriction and improves flow.
The 289 High Performance exhaust port is the same as the 2V/4V exhaust port. Note here the “4V” cast marking. Expect to see cavity numbers 19, 20, or 21 for 289 High Performance cylinder heads.
Beginning in 1964, Ford increased the small-block Ford valve size to 1.780/1.450 inches. The combustion chamber size also increased to 54.5 cc for 1964. Casting numbers are C4OE-B, C5OE-A, and C5AE-E.
Despite the 289 High Performance head’s reputation for rarity and value, much better aftermarket heads are available. When originality is important in a restoration, there’s no substitute for the 289 High Performance head. Rarity affects price, which is important to remember when you’re looking for Hi-Po heads. Some have sold for $1,000 per pair. If performance is your only goal, however, don’t waste money on a 289 High Performance head. The aftermarket offers a great cylinder head selection.
302
The 302 has virtually the same cylinder head casting as the 289 with the same port and valve sizing along with similar combustion chamber sizing. The decidedly rare 1968 302-4V head is unique for its smaller 53.5-cc chambers, which increase compression. Compression is this cylinder head’s only advantage. It’s a good cylinder head for any 289/302 Ford if you want to increase power. The 4V head has the same-size valves and ports as the 289.
The 302-2V head for 1968 has larger 63-cc chambers to lower compression and reduce emissions.
Look for casting numbers of C7OE-C, C7OE-G, C8AE-J, C8DE-F, C8OE-J, C8OE-M, C8OE-K, and C8OE-L.
Like 289 heads, all 302 heads are the same except for Thermactor air-injection pump provisions. The truck head, C9TE-C, employs a 58.2-cc chamber for slightly higher compression. Ultimately, all 302 heads were carryovers of the 289 head castings, making them interchangeable.
When it comes to interchanging cylinder heads, the most important consideration is chamber size and its effect on compression. As federal emissions standards became stricter, chamber size grew larger, further reducing compression for use with lower-octane, low-lead, or no-lead fuels. Most 1970s 302 heads had 58-cc chambers, the same port size, and 1.780/1.450-inch valve size.
Casting numbers to watch for are D1TZ-A, D5OE-GA, D5OE-A3A, and D5OE-A3B. Beginning with the D5OE head, Ford eliminated the Thermactor manifold bungs on the exhaust side and went to a common internal air injection manifold that ran the length of the head and reduced exhaust port restriction.
Beginning in 1977, chamber size increased to 69 cc to further reduce the 302’s compression ratio. These heads are numbered D7OE-DA and D8OE-AB, which are undesirable castings, no matter what you do with them.
In 1979, Ford introduced a D9AE the 302/351W cylinder head casting very similar to the D7OE and D8OE castings with 67- to 70-cc chambers.
The D9AE-6049-AA casting was in production until 1985. When Ford went to roller tappets and a new 5.0L roller block in 1985, it also released a new E5AE-6049-CA head casting designed to clear roller tappets, making it possible to replace these lifters without removing the cylinder heads.
For 1986, Ford went with the E6AE-6049-AA casting with “High-Swirl” chambers. Ford used this head on the 1986 5.0L High Out-put V-8 with Sequential Electronic Fuel Injection (SEFI).
Purpose-cast 302 heads are marked “302.” This is a C9TE truck casting with a single bump above the 302, also known as the “E” head.
The 1969 302 C9TE “E” truck head has a 69-cc chamber. It is clearly larger than the 289/302 55- to 57- and 60-cc chamber. Valve and port sizing remains the same.
For 1987, cylinder head selection changed again, with two types: the E7TE-6049-PA head with fast-burn chambers and existing-stock E5TE- 6049-PA, a truck head. The E7TE-PA head was the most common casting used through 1995.
The 1993–1996 GT-40 cylinder head (F3ZE-6049-AA) was used in the Mustang Special Vehicle Team (SVT) Cobra and Lightning F150 pickup. It was a modest improvement over the E7TE-PA casting thanks to smaller 60- to 63-cc chambers and larger 1.840-inch (intake) and 1.540-inch (exhaust) valves. It can be identified by three vertical ribs cast into each end of the cylinder head. Sometimes, there’s a “GT” cast into the same area, but very few were made that way.
The F3ZE-AA head evolved into the F4ZE-AA service head for 1994; they were virtually identical in appearance. The GT-40 head is a good budget casting because not only did Ford cast this head for the Mustang, but for Ford Motorsport SVO, Ford’s aftermarket performance parts group, as M-6049-L302. Swap meets are crawling with these heads.
When the 5.0L High Output engine became a Ford Explorer and Mercury Mountaineer option in the late 1990s and early 2000s, Ford produced an odd-duck cylinder head for this engine designed to reduce emissions while boosting power. This head is known as the GT-40P or “P” head (F7ZE-AA) designed specifically for Explorer/Mountaineer.
The “P” head has a reduced spark plug angle where the firing tip has been moved closer to mid-chamber. The intake valve size is the same as on a GT-40 at 1.840 inches. However, the exhaust valve size is smaller at 1.460 inches. The problem with this cylinder head is using it in anything but an Explorer/Mountaineer because spark plug angle presents header and exhaust manifold clearance issues.
255
In its quest for reduced fuel consumption, Ford introduced the 255-ci small-block in 1980. This short-lived engine lasted just three model years, through 1982. Ford reduced the 302’s 4.000-inch bore to 3.680 inches and kept the same 3.000-inch stroke to achieve 255 ci and satisfy federally mandated corporate average fuel economy (CAFE) numbers. The 255 head (E0SE-AB) with its small 53- to 56-cc chambers and 1.680/1.460-inch valves is a unique casting with small, round, restrictive intake ports to improve emissions and fuel economy.
Although many Fox-Body Mustangs were produced with this engine in 1980–1982, it was never conceived with performance in mind.
351W
Because the 351W has a greater displacement, it has larger valves than its 289/302 counterparts. This makes the 351W head a nice performance upgrade for a 289/302 engine if you want a stock look and factory iron heads. If you’re building a 351W, it’s important to know which head castings work best for your Windsor.
The most desirable 351W head castings are C9OE-B, C9OE-D, D0OE-C, D0OE-G, and D0OE-C. All of them have the same 60.4-cc chamber and 1.840/1.540-inch intake/exhaust valves. Truck heads have larger 69-cc chambers for reduced compression.
Here’s the 1975 351W cylinder head with 69-cc combustion cham-bers and 14-mm spark plugs. The “WCP” marking (upper right corner) means that this head was cast at the Windsor, Ontario, iron foundry. It is unknown what the “20A” marking (lower left corner) means.
A closer look at the 1975 351W head casting shows the “WCP” and “351” markings. When you are shopping for 351W cylinder heads, focus on 1969–1974 castings with the 60-cc chamber and 1.840/1.540-inch valves. By 1978, the 351W head was noth-ing more than a 302 casting with smaller 1.780/1.450-inch valves. A popular misconception is that the 351W head has larger ports. In reality, port sizing is the same as on the 289/302. Only valves are larger through 1977.
The 1969–1974 351W 60-cc combus-tion chamber is shaped like a shovel and equipped with the 18-mm spark plug. Valve sizing is 1.840/1.540 inches. Port sizing is 1.94 x 1.76 inches intake and 1.24 x 1.00 inches exhaust.
Beginning in 1975, the 351W chamber grew to 69 cc and was more rounded with a 14-mm spark plug hole. Port and valve sizing remained the same; however, compression was lost with the 69-cc chamber.
Beginning in 1978, the passenger- car 351W chamber grew to 69 cc for lower compression. The number to watch out for here is D8OE-AB; it’s the 351W head to stay away from. This casting is basically a 302 head with smaller 1.780/1.450-inch valves and the 69-cc chamber. Ford went to smaller valves for improved emissions and better low-end torque.
As 351W production continued into the 1980s, not much changed, with cylinder head castings differing very little from the 302.
When Ford produced the limited- production SVT Lightning F150 pickup in the early 1990s, the 351W/5.8L engines received the same GT-40 cylinder heads as the 1993–1995 Mustang SVT 5.0L Cobra. This makes your cylinder head search easy if you’re building an F-150 Lightning 5.8L High Output. Your objective needs to be torque, not necessarily horsepower.
351C/351M/400
The 335-series Cleveland engines are grouped together here because they’re basically the same engine architecture with the same selection of cylinder heads. Selection among the four basic variations of the Cleve-land cylinder head depends on how you intend to use the engine.
The 351C-4V cylinder head is the most desirable casting because it has huge intake ports and valves along with high-compression wedge chambers, which offer excellent quench and high compression. If you want 351C-4V heads, look for a D0AE-H or D0OE-R with Holland Tunnel–size 2.500 x 1.750-inch intake ports and 61- to 64-cc wedge chambers. This is a great cylinder head for high-RPM operation because it flows so well and offers the power advantage of compression. Just keep in mind the available fuel octane, spark timing, and fuel mixture.
There are two types of 351C open chamber (low-compression) heads: 2V and 4V. Neither is the most desirable casting for real performance use. However, Tim Meyer of TMeyer Precision Automotive Machining says the 351C-2V open chamber heads work quite well for street performance use thanks to modest port and valve sizing, which improves low- to mid-range torque. A fundamental shortcoming of the 351C open chamber head is poor quench, which makes these heads prone to pinging or spark knock regardless of how you tune the engine. Apply light throttle under load and you get spark knock. In fact, you can goose the throttle in neutral and get spark knock. The main thing is to keep compression conservative with these heads.
The 351 Cleveland 4-barrel cylinder head is easily the greatest Ford production head thanks to its 61- to 64-cc wedge chambers and cocktail table–size 2.190/1.710-inch intake/exhaust valves. Drive-through intake ports measure 2.50 x 1.74 inches (huge passages) and flow very well at high RPM. They were never designed for low- to medium-range street torque. Tight wedge chambers offer great quench.
Although this looks like a 351C-4V cylinder head, it is a Boss 302 cylinder head modified to fit a 351C-4V engine. The difference is the cooling passages (arrows) bored into the casting of a 351C engine. This cylinder head was removed from a 351C-4V engine during a rebuild. The builder, MCE Engines, was surprised to discover its Boss 302 status and the Cleveland cooling passages plugged with epoxy.
The poly-angle-valve 351C cylinder head is legendary for its performance potential. If you can find the optimum combination of 351C-2V ports and 351C-4V chambers in an Australian Cleveland head, it’s a great off-the-shelf cylinder head. Be advised: The Aussie Cleveland head is scarce and expensive. This is a North American 351C-4V head cast at the Cleveland foundry with a “CF” logo.
This is a 351C-4V 61- to 64-cc chamber with huge 2.190/1.710-inch intake/exhaust valves. Because this is such a compact chamber and so well thought out, it offers great quench and is less prone to detonation. On a stock 351C-4V engine, it yields 11.0:1 compression.
The 351C-4V can easily boast having the largest intake ports of any domestic V-8 engine of the era including the Chrysler Hemi. It’s great to spin a Cleveland to 6,000 to 7,000 rpm because that’s where horsepower and torque connect and become very productive when the pedal meets the metal. On the street, low- to mid-range torque is poor with this head because you just don’t have the velocity at low RPM that yields torque.
This “4” with a bump indicates a 351C-4V cylinder head. In more than 30 years of automotive writing and dozens of Cleveland castings, I can say with great confidence that this “4” marking always means it’s a 4V head. However, always check combustion chamber sizing before buying. Some 351C-4V heads have the 61- to 64-cc wedge chamber (1970–1972) and some 351C-4V heads have the 74- to 77-cc open chamber. The difference can mean an 11.0:1 or 9.5:1 compression ratio.
Despite the 351C-4V cylinder head’s great intake port sizing, the exhaust ports can be restrictive, depending on how you intend to use them. With port and bowl work, you can achieve improved scavenging.
When you’re searching for 351C cylinder heads, watch out for the rocker arm pedestal type. It has a bolt-fulcrum pedestal designed for a bolt-fulcrum rocker arm, which is the “set it and forget it” no-adjust rocker arm. You can machine this pedestal for a screw-in stud-mounted adjustable rocker arm with pushrod guide plates.
This Boss 351C cylinder head has a screw-in stud pedestal. The Boss and High Output heads were the only 351C cylinder heads cast for screw-in stud-mounted rocker arms and guide plates. The trick is distinguishing between the 1971 Boss and the 1972 High Output. The Boss D1AE casting has 61- to 64-cc chambers. The 1972 D2AE High Output head has the large 71- to 77-cc chamber. Although the 1972 head is rare, the 1971 head is more desirable.
The more conservatively sized 351C-2V intake ports are virtually identical to Australian 351C-4V and 302C intake ports. This is generous port sizing for the street because you get great low-end torque.
This side-by-side comparison shows the 351C’s two combustion chambers. On the left is the 71- to 77-cc open chamber head casting for 1970–1974 351C-2V, 1972–1974 351C-4V, 1972 351C-4V High Output, 1975–1982 351M, and 1971–1978 400. On the right is the 1970–1974 61- to 64-cc 351C-4V wedge chamber. Although the Ford Master Parts Catalog shows variations in chamber sizing across these heads, they consistently show 71 to 77 cc and 61 to 64 cc through many engine builds.
The 351C-2V open chamber head was used from the beginning in 1970 (D1AE-AA and D1AE-CB) and continued with the 351M and 400 engines.
The 351C-4V open chamber head (D1ZE-DA and D1ZE-GA) offers very little in terms of performance because its chamber design loses compression and aggravates spark knock. What’s more, the 351C-4V open chamber head’s large ports and valves contribute nothing to street torque. The 351C-4V open chamber head is the least desirable of all 351C heads.
Open chamber 2V and 4V heads (74.7- to 77.7-cc chambers) net 9.5:1 compression depending on piston selection. By comparison, the 351C-4V closed wedge chamber head (61.3- to 64.3-cc) makes 11.0:1 compression, depending on piston selection and compression height.
A good street performance head for the 351C/351M/400 is the Australian 351C head sporting smaller 64- to 67-cc wedge chambers with the correct size 2-barrel ports for excellent low- to mid-range torque. These cylinder heads aren’t always easy to come by, but they’re out there.
CHI Aftermarket Heads
There was a time when your only choices of Cleveland engines were factory iron heads you could improve with some good port work. Today, you can take your pick of terrific aluminum castings for the Cleveland. The most common high-performance cylinder heads are the iron and aluminum alloy castings from Cylinder Head Innovations (CHI) in Australia. They are available from a number of sources in the United States in a wide variety of configurations. CHI has invested tremendous amounts of time in Cleveland head technology, and its cylinder head has competed successfully at the Engine Masters Challenge.
CHI has made the most of the Cleveland’s great potential with right-size ports, ports large enough to flow generous amounts of air and hot gases, yet small enough to make velocity. With velocity comes torque, and torque is what you want for the street and weekend racing. In road racing, torque thrusts you out of turns and down straights. In drag racing, you want torque coming off the line under hard acceleration. And with the right head, cam, and induction combination, torque hands off to horsepower at high RPM.
2V, 3V, 4V Cleveland Heads
CHI offers the 2V, 3V, and 4V as bare or complete in ascast or CNC ported heads. The 2V head, as its designation indicates, has the 351C-2V (2-barrel) port configuration. The 4V head has 351C-4V port sizing. The 3V head has the airflow potential of the 4V head with 2V port sizing. The 3V is a great compromise between the 2V and the 4V.
Engine builders such as Jon Kasse and Darin Morgan have been able to massage these legendary cylinder heads and make a lot of power. CHI heads are completely manufactured in-house from foundry to finished product. This enables CHI to maintain high-quality standards.
CHI 3V Iron Head
The CHI 3V castiron Cleveland head is an iron version of its aluminum 3V brethren with the same chamber, valve sizes, and port configurations. CHI conceived the 3V iron head for racing classes where aluminum heads are not permitted, yet it has many of the same benefits of the alloy head.
Depending upon how you configure your Cleveland package, the 3V iron head can deliver upward of 500 hp and comparable torque with standard displacement. If you dial in more displacement, horse-power and torque go up accordingly. Because the iron 3V head is available on a very limited basis (for racers primarily), availability is inconsistent. In truth, this is not a head that the average street enthusiast will want. Why order iron when you can shave weight (and heat) and have aluminum?
If you find Australian 302C or 351C head castings, you won’t find a Ford North American casting number. Expect to see something like this “30J6” marking.
Here’s a rare casting not often seen in the Northern Hemisphere: the Australian 302 Cleveland cylinder head with supercompact 56- to 59-cc wedge chambers.
At a glance this cylinder head resembles a 351C-4V. However, you can tell that it is a Boss 302 casting by the missing cooling passages common to a 351C. Study the deck surfaces closely and you’ll notice a 289/302 cooling passage pattern.
Edelbrock also produces an Australian-style 351C aluminum cylinder head, which offers lightweight design, good temperature dissipation, and improved airflow. It is a nice alternative to the iron Ford head.
Boss 302
The 1969–1970 Boss 302 cylinder head is little more than a specially machined 351C-4V head casting revised for use on a Boss 302 block. The primary difference between the heads is the cooling passage routing; the 351C has a dry intake manifold and the Boss 302 is wet. Coolant is routed through the intake manifold with the Boss 302 instead of across the block as with the 351C.
You have three basic Boss 302 cylinder head castings to choose from: C9ZE-A with 63-cc chambers and huge cocktail table–size 2.230/1.710-inch valves, D0ZE-A with smaller 58-cc chambers and 2.190/1.710-inch valves, and D1ZE-A service head also with 58-cc chambers and 2.190/1.710-inch valves. Ford went to a smaller 2.190-inch intake valve with the D0ZE-A and D1ZE-A head castings to improve low-end torque. However, these smaller stop-cocks do very little for low-end torque.
Although the Boss 302 cylinder head is a 351C-4V casting, it was cast with its own Ford casting number, in this case D0ZE-6090-A, specifically for Mustang although there were Boss 302 Cougars.
Another unique nuance to this 1970 Boss 302 head casting is the “WF” Windsor foundry casting code. It’s proof that not all of them were cast at the Cleveland foundry.
This Boss 302 cylinder head is receiving mill work at JGM Performance Engineering. Close inspection of the Boss 302 cylinder head proves that you can modify a 351C-4V head for use on a Boss 302 (and vice versa) because the basic casting is the same. All you have to do is close cooling passages with an epoxy resin filler and machine the head for either a Boss 302 or 351C-4V engine. You can also do the same with a 289/302/351W engine to create a Cleveland.
This Boss head was found on a 351C-4V engine. Because the Boss 302 has a “wet” intake manifold, cooling passages were cast into the head for cross flow through the intake manifold. The 351C has a “dry” intake manifold, making these passages unnecessary. They were filled with epoxy for use on a 351C.
Ford’s Boss 302 was never intended to be a low- to mid-range RPM street engine. It does its best work at high RPM on a racetrack and was born for road racing. The Boss 302 head can easily be compared to the Boss 351 head with pushrod guide plates and screw-in rocker arm studs.
“Aftermarket” Cylinder Heads
The broadest selection of aftermarket cylinder heads really isn’t found in the aftermarket, but from the factory. Ford Performance (formerly Ford Racing and Ford Motorsport SVO) has offered the performance enthusiast many options. Selection isn’t what it used be because Ford Performance focuses on the Modular and Coyote engines today. Some of these time-proven heads are still available. Others have been discontinued and are available either used or as NOS in their original packaging.
The cool thing about Ford Performance aftermarket heads is the ease of selection along with their simplicity. You don’t have to search for factory iron castings such as 289 Hi-Po or 351W heads anymore. Ford Performance, or the used aftermarket, has a cylinder head for virtually every application.
The most common Ford aftermarket head is the GT-40 High Flow, available in iron or aluminum. If you want a more stock appearance that offers an improvement in performance, the GT-40 is a good choice. The GT-40, with good port, bowl, and chamber work, improves horsepower on the high end thanks to 1.840/1.540-inch intake/exhaust valves, which can be grown easily to 1.940/1.600 inches (Chevrolet intake valve size). The GT-40’s 65.5-cc chambers are a nice compromise between older 54- to 55-cc and 70-plus-cc chambers. You can mill this cylinder head’s deck surface to reduce chamber size and raise compression.
The GT-40 Turbo-Swirl cylinder head is now known as the M-6049-X306 and M-6049-X307 for 289/302/351W engines. The X306 aluminum head has a 64-cc chamber; the X307 head has a 58-cc chamber. Intake ports flow 240 cfm at .550-inch lift. Exhaust flows 170 cfm at .500-inch lift. This head is machined for 1.940/1.600-inch intake/exhaust valves.
This threaded insert plugs up the Thermactor smog-pump passages in late-model small-block Ford cylinder heads, enabling you to run late-model cylinder heads on a vintage small-block. The plugs can be sourced from nearly any auto parts store and Summit Racing Equipment.
Your pistons must have valve reliefs to reduce the risk of valve- to-piston contact. You must also check intake manifold port compatibility by doing a gasket match. The nice thing about the GT-40 head is its compatibility with just about any small-block intake manifold or header.
The Z aluminum cylinder head is a great alternative to the Turbo-Swirl for daily driving and weekend racing. Made of A356 T6 cast aluminum, the Z head offers improved flow numbers and more power if you give it your best attention. The Z mandates a competition valve job and bowl work. It is a CNC-ported head you can buy from Ford Performance. You get premium stainless-steel 2.020/1.800-inch intake/exhaust valves for more horsepower and improved midrange torque. Beehive valvesprings eliminate valve float. Laser-cut guide plates yield perfect fit. Expect 319.7-cfm intake flow and 227.7-cfm exhaust at .550 inch.
The castiron Ford Performance Sportsman head (M-6049-N351) is a nice compromise between the Z, GT-40 Turbo-Swirl, and the Yates NASCAR head. It has 2.020/1.600-inch valves for improved flow with 64-cc chambers. This head is usually suggested for 351W engines, but can be used on the 289/302 with a head bolt adaptor kit. The Sportsman head accepts an M-6569-C351 stud girdle.
The Robert Yates High-Port aluminum head is a NASCAR-level race head (M-6049-C3) sporting a 40-cc chamber. It comes bare and you choose what goes inside. The M-6049-C3L Yates head has 67-cc chambers for reduced compression. Huge 2.100/1.600-inch intake/exhaust valves occupy both heads. Because this is an all-out race head, it is not suggested for the street. But it is surely a Ford cylinder head. And because it is a race head, you can plan to make all kinds of modifications.
Valvecovers
Small-block Ford valvecovers are a study in change both internally and externally. Sometimes changes in valvecover shape were made because of changes inside the engine, such as rail-style rocker arms in mid1966, which made it necessary to “pent roof” the 289’s valvecovers to clear the rail-style rocker arms. The 335 series Cleveland engines didn’t experience much change over their long production life. Aside from steel versus finned cast aluminum, the Cleveland valvecover was virtually the same from beginning to end. The Boss 302 valvecover is nothing more than a 351C valvecover, be it steel or cast aluminum.
All small-block Fords were topped with “slope-side” stamped-steel valvecovers from 1962 to 1966. The earliest 221 and 260 engines didn’t have an oil filler neck in the valvecover, but instead a filler tube in the timing chain cover. This is a 1965 289-4V engine with the California emissions closed crankcase ventilation filler cap.
On May 2, 1966, Ford redesigned the 289 valvetrain to a rail-style rocker arm instead of a pushrod guide cast in the cylinder head. Because the rail-style rocker arm created clearance issues with the slope-side valvecover, Ford designed a new pent-roof flat-top valvecover, which ran through the 1967 model year.
This 1967 289 High Performance V-8 has a chrome flat-top pent-roof valve-cover. Although this valvecover was designed for the rail-style rocker arm, the 289 High Performance V-8 was never fitted with rail-style rocker arms.
During the 1966 model year, Shelby went to solid-letter finned aluminum valvecovers with a black wrinkle finish. You could also have solid-letter Cobra valvecovers in a natural aluminum finish.
Here’s a Cobra dress-up kit with hollow-letter cast aluminum Buddy Bar valvecovers. Buddy Bar is an aluminum casting operation in Los Angeles that produced aluminum castings for Ford and Shelby American.
Beginning in the 1968 model year, Ford added “Power By Ford” to the pentroof flat-top stamped steel small-block valvecover.
Ford used a pent-roof stamped steel small-block valve-cover in 1975. This valvecover continued into the early 1980s. Note the PCV valve and oil filler cap combination, which first arrived on the 351C engine in 1971.
When Ford introduced SEFI for 1986, it came with these cast-aluminum valvecovers, which were in production until 1994.
These black recessed stamped steel valvecovers arrived with the 1993 SVT Cobra GT-40 V-8 and continued through the end of 5.0L and 5.8LW production.
The broad-shouldered, finned cast- aluminum Cleveland valvecover arrived for 1970 on the Boss 302 engine. Ironically, it did not appear on the 351C engine until 1971. All 1969 and very early 1970 Boss 302 engines were fitted with chromed stamped steel 351C valvecovers.
This stamped steel 351C/351M/400 valvecover was commonplace from 1970 to 1982.
The 1971 Boss 351C engine was fitted with finned cast-aluminum pent-roof valvecovers, which first appeared on the 1970 Boss 302.
Written by George Reid and Posted with Permission of CarTechBooks
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