Engine technology has come a long way since the small-block Ford V-8 was introduced in 1962. When Ford was developing the 221/260 small-blocks at the beginning of the 1960s, there was no such thing as a small-block or a big-block. These were just V-8 engines, much as the Chevrolet 265 and 283 were. The Chevy V-8 and the new small Ford V-8s differed from tradition with a skirtless block design and the large bore and relatively short stroke.
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A large 4.000-inch bore and a short 2.870-inch stroke begged the question of how it would make a lot of power. It really did change how you approached the making of power. You had to learn how to make power with less displacement. If you’re building a stock small-block Ford, you don’t have to think much further than an off-the-shelf flat-tappet hydraulic or mechanical camshaft. However, if you’re building a small-block Ford for daily driving, weekend getaway, or all-out performance, you need to put more thought into cam and valvetrain selection. You want plenty of low- to mid-range torque for good acceleration. You also want improved fuel efficiency and longevity.
Cam Selection Considerations
Proper cam selection depends on what you want your small-block Ford to do. Even if you’re building a mild small-block for the morning commute, you should choose a roller-tappet hydraulic camshaft as a performance enhancer and friction reducer because you’re also building efficiency into the engine. The decision to go with a roller cam depends on budget. Not everyone can afford it. Although roller cams and roller rocker arms cost a lot more going in, they pay off in power and efficiency over the lifespan of an engine.
Airflow and Fuel
Camshaft selection for the street should focus on a civilized idle with 18 to 22 inches of mani-fold vacuum. Vacuum is important to performance. It is also vital to vacuum-operated accessories such as climate control and power brakes. If you want a more aggressive sound with a “rumpity-rump-rump!” idle, you want to focus on lobe centers and valve overlap.
However, expect to sacrifice low-end and mid-range torque when you turn your attention toward horse-power. It is challenging to achieve both horsepower and torque, especially with a carbureted small-block. Horsepower has little or no value on the street. However, it becomes a high priority on the racetrack where engines rev high and both horsepower and torque unite to become speed.
Camshaft profiles are rooted in what you want the camshaft to do. And because camshaft-speak is wild-weird science for most people, it becomes challenging to choose the right cam for your application. The objective is to draw as much air and fuel into the cylinder as possi ble as early as possible to make the most of the light-off. Fuel and air do not “explode” in the combustion chamber. Instead, the ignition of air and fuel is more like a quick fire (a light-off) as with your water heater or furnace when the gas valve opens and the gas ignites. Heat and pressure act on the piston and crank where linear motion becomes rotary motion. To make the most of heat and pressure, you need just the right valve timing, which depends on what you want the engine to do.
Low-end torque on the street calls for different valve timing events than high RPM on a race track. And remember, there are no free lunches when it comes to camshaft profile. It is nearly impossible to have both low-end and high-RPM benefits in a single camshaft; that’s because engines employ different dynamics at low and high RPM. Power is made differently at low RPM than it is at high RPM.
Airflow through an engine takes on a momentum, which is where camshaft profiling and piston timing can become rather complex. You want airflow to behave one way down low (velocity at low RPM) and another way up high (velocity at high RPM). It is volume and velocity that make power.
In a perfect world, cam timing works out when the intake valve opens at exactly top dead center (TDC) and closes at bottom dead center (BDC). Unfortunately, it has never worked that way with four-cycle piston engines because it’s a momentum thing with internal combustion engines.
Because valves open and close gradually, you must plan for that slow response by opening the intake valve before TDC and closing it after BDC. Add to that the speed with which air moves through the induction system and intake port. The way the intake valve opens and closes is dependent upon engine speed (RPM). The higher the RPM, the later the intake valve should close. By the same token, the earlier it closes the more low- to mid-range torque you have.
The camshaft turns at one-half crankshaft speed for a 2:1 ratio. And that creates the four cycles of intake, compression/ignition, power stroke, and exhaust. Your small-block’s crankshaft makes two complete revolutions (720 degrees of rotation) for every one camshaft revolution or four complete cycles. Flat-tappet camshafts work differently than roller camshafts, which means you have to approach each type differently. Flat-tappet camshafts limit what you can do with lobe profile if you want streetability. If you want an aggressive profile with flat tappets, you can only go so far with a street engine or suffer with poor drivability (rough idle, low manifold vacuum). If you want an aggressive profile in a street engine, I suggest stepping up to a roller camshaft, which can handle the aggressive profile better using roller tappets.
The best street performance cams are ground with a lobe separation between 108 to 114 degrees. When you keep lobe separation above 112 degrees, you improve drivability because the engine idles smoother and makes better low-end torque. You also have more intake manifold vacuum at idle for accessories such as power brakes. When lobe separation goes below 108 degrees idle quality and streetability suffer. But there’s more to cam selection than just lobe separation.
Compression and cam timing must be considered together because one element always affects the other. Valve timing events directly affect cylinder pressure and ultimately affect working/dynamic compression. Long intake valve duration reduces cylinder pressure. Shorter intake duration increases cylinder pressure. Too much cylinder pressure can cause detonation (pinging). Too little and you lose torque.
You can count on cam manufacturers to figure stock compression ratios into their camshaft selection tables, which makes choosing a camshaft easier than it’s ever been. Plug your application into the equation and you will be pleased with the result most of the time. If you’re a novice, you need to be conservative with cam specs if you want reliability and an engine that will live a long time. Stay with a conservative lobe lift profile (less than .500-inch lift). High lift camshafts are hard on the valvetrain. They also put valve-to-piston clearances at risk. Watch duration and lobe separation closely, which helps you to be more effective in camshaft selection. Instead of opening the valve wider (lift), you want to open it longer (duration) and in better efficiency with piston timing (overlap or lobe separation).
Before selecting a camshaft, always consider what you have for induction, heads, and exhaust. The savvy engine builder understands that to work effectively, an engine must have matched components. Cam, valvetrain, heads, intake manifold, and an exhaust system must all work in harmony or you’re just wasting time and money.
If you will use stock cylinder heads, your cam profile should not be too aggressive. Opt for a cam profile that gives you good low- to mid-range torque. Torque doesn’t do you any good on the street when it arrives at 6,000 rpm. Choose a cam profile that makes good torque between 2,500 and 4,500 rpm.
Another thing to remember with camshaft selection is how the cam works with your engine’s cylinder heads. Take a close look at valve lift with a particular cylinder head and determine its effect. Some camshafts actually lose power with a given head because there’s too much lift or duration. This is why you want to be familiar with a cylinder head before choosing a camshaft. You want to seek optimum conditions with any cylinder head/camshaft combination.
The type of fuel you run also affects camshaft selection. You can actually raise compression if you’re running a mild camshaft profile or using a higheroctane fuel. Camshaft timing events must be directly tied to compression ratio. The longer the duration, the lower the cylinder pressure and working compression. The shorter the duration, the less air you bring into the cylinder, which also affects compression.
The objective needs to be the highest compression possible without detonation. With this in mind, you want the most duration possible without compression extremes. Duration gives you torque as long as compression is sufficient.
As you know, valve overlap is the period between exhaust stroke and intake stroke when both valves are slightly off their seats. This occurs to improve exhaust scavenging and cylinder filling. It improves exhaust scavenging by allowing the incoming intake charge to push the remaining exhaust gases out via the closing exhaust valve. Were the exhaust valve completely closed, you wouldn’t have scavenging.
The greater the overlap in a street engine, the less torque the engine makes down low where you need it most. This is why you want less valve overlap in a street engine and more overlap in a racing engine, which makes its power at high RPM. Increased valve overlap works best at high RPM.
Street engines need 10 to 55 degrees of valve overlap to be effective torque powerhouses. When valve overlap goes above 55 degrees, torque on the low end falters. A really hot street engine needs greater than 55 degrees of valve overlap, but not much greater. Racing engines need 70 to 115 degrees of valve overlap at high RPM.
For a street engine, you want valve overlap to maximize torque, which means taking a conservative approach. Push overlap as far as you can without compromising torque. You also have to figure in lift and duration with valve overlap to see the complete power picture.
Lobe Separation Angle
Another area of consideration in street cam selection is lobe separation angle. You choose lobe separation based on displacement and the way the engine will be operated. Consider lobe separation based on how much displacement and valve size you will use.
The smaller the valves, the tighter (fewer degrees) the lobe separation should be. However, tighter lobe separation does adversely affect idle quality. This is why most cam-shaft manufacturers spec their cams with wider lobe separations than the custom grinders do.
Duration and Compression
Duration in a street engine is likely the most important dynamic to consider in the camshaft selection process. You increase duration whenever less lift is desired. Why? Because you introduce airflow into the cylinder bore in two ways, lift and duration. You can open the valve more and for less time to get airflow. Or you can open the valve less and keep it open longer via duration to increase airflow. Each way has a different effect on performance.
Duration is determined by the size of the cylinder head, how much displacement you have, and how the engine will be used. Excessive duration hurts low-end torque, which is what you need on the street. So you have to achieve a balance by maximizing duration without a loss in low-end torque. You do this by using the right heads with proper valve sizing. Large valves and ports don’t work well at all for street use. Dial in too much duration and you have no power at the traffic light.
So what does this tell you about duration? You want greater duration whenever displacement and valve sizing go up. Increasing duration falls directly in line with torque peak and RPM range. This does not mean you necessarily gain any torque as RPM increases. It means the peak torque simply comes in at a higher RPM range.
For example, if the engine makes 350 ft-lbs of torque at 4,500 rpm and you increase duration,you may well be making the same amount of torque at, say, 5,200 rpm. In short, increased duration does not always mean increased torque.
Compression has a direct effect on duration. When you run more compression, you have to watch duration closely because it can drive cylinder pressures too high. Sometimes you can curb compression and run greater duration, depending on how you want the engine to make power. With greater duration, an engine makes more power on the high end and less on the low end. This is why you must carefully consider duration when ordering a camshaft.
Higher compression with a shorter duration helps the engine make torque down low where you need it most in a street engine. The thing to watch for with compression is detonation and overheating. Maximum street compression should be around 10.0:1.
Also pertaining to an engine’s needs is valve lift. Small-blocks generally need more valve lift than big-blocks. As lift is increased, so is torque. This is especially important at low- and mid-RPM ranges where it counts on the street. Low-end torque is harder to achieve with a small-block because these engines generally have short strokes and large bores. Your objective needs to be more torque with less RPM if you want your engine to live longer. High revs drain the life out of an engine more quickly.
To make good low-end torque with a small-block, you need a cam-shaft that offers a combination of effective lift and duration. As a rule, you need longer intake lobe duration to make the most of valve lift. But rocker arm ratio is the other half of the equation. The most common rocker arm ratio is 1.6:1, which means the rocker arm gives the valve 1.6 times the lift than at the cam lobe. When you step up to a 1.7:1 ratio rocker arm, valve lift becomes 1.7 times the lift at the lobe.
It is best to choose a conservative cam profile, especially if you’re building an engine for daily and weekend race use. Whenever you opt for an aggressive camshaft with a lot of lift, you put more stress on the valvestem, guide, and spring. The constant hammering of daily use with excessive lift can kill an engine without warning.
Rocker Arm Tip
It is vital that you confirm proper centering of the rocker arm tip on the valvestem tip when you set up the valvetrain. You do this by using the correct-length pushrod for your application. If tip centering is in doubt you can use a pushrod checker. It’s an adjustable pushrod used to properly configure a small-block’s rocker-to-stem geometry.
If the pushrod is too long, the tip is “undercentered” on the valvestem, causing excessive side loads toward the outside of the cylinder head. If the pushrod is too short, the rocker arm tip is “over-centered,” causing excessive side loading toward the inside of the head. In either case, side loads on the valvestem and guide cause excessive wear and early failure. This is why you want the rocker arm tip to be properly centered on the valvestem, and for smooth operation.
A roller tip rocker arm is an accessory that reduces valvestem tip wear and side loading. Roller tip rocker arms roll smoothly across the valvestem tip, virtually eliminating wear. Stamped-steel, roller tip rocker arms are available at budget prices; they don’t have the added cost of extruded or forged parts.
Camshaft selection, along with rocker arm type, has a more direct effect on an engine’s performance than any other element because you can control valve lift via rocker arm ratio and lobe lift. With respect to factory camshaft grinds, you have a wide variety of choices. However, unless you are seeking a spot-on factory feel and performance, there’s not much point in using a factory grind because modern technology is an improvement over the factory offerings.
When you’re planning camshaft selection keep firing order in mind. Small-block Fords (221/260/289/302) prior to 1982 had a firing order of 1-5-4-2-6-3-7-8. When Ford introduced the 5.0L High Output engine in 1982, it opted for the Marine cam for power, which had the 351W firing order: 1-3-7-2-6-5-4-8.
Ford used the 351W firing order to improve crankshaft loading. This means a more even distribution of power across the main journals. It has been said that there were crankshaft breakage issues with the 1-5-4-2-6-3-7-8 firing order and lighter 5.0L crankshafts; however, this has never been confirmed by Ford.
The 351W Marine camshaft was an off-the-shelf item Ford could slip into the 5.0L engine and make more power without doing much else.
Spring pressure and cam profile (lift primarily) must be compatible. Not enough spring pressure and you float the valves at high RPM. Too much spring pressure and you wipe out cam lobes. In the good old days, Ford marketed a great concoction called Ford Oil Conditioner (C2AZ-19579-A) in 1-pint cans. Today, you’d call it a zinc additive (such as ZDDP), which reduces engine wear, especially during break-in when flat tappets and cam lobes are getting to know one another.
What this means for you 50 years later is that regardless of whether you have a flat-tappet camshaft or a modern roller, ZDDP should be used as a friction reducer to minimize engine wear, especially when an engine is fresh.
Today’s camshaft aftermarket offers the greatest selection of camshafts in performance history that far outperform what was available long ago. Although roller cams and rocker arms are expensive, they’re worth every dime of better performance, better efficiency, and reduced wear.
Reduced internal friction is everything to power gains. You can run a more aggressive lobe without the struggles of a hot cam. The nice thing about roller cam technology is its invisible status. It’s in there, but no one knows it is. If you’re running a 289 High Performance or Boss 302, you can actually run a hydraulic roller cam and get the same sound without having to perform periodic valve adjustment. Much depends on how high you intend to rev the engine.
When it comes to high-end performance, there’s no substitute for a hot mechanical roller camshaft.
You’ve undoubtedly heard the term “dual-pattern” camshaft. A dual-pattern camshaft runs different profiles on the intake and exhaust side to meet a specific need. I run dual-pattern profiles whenever I’m pushing the revs up. Typically, a dual-pattern camshaft runs a shorter exhaust valve duration due to less time required to scavenge the exhaust gases at high RPM. It is also beneficial with nitrous or supercharging/turbo-charging where exhaust scavenging is rapid and furious.
Running a dual-pattern camshaft on the street makes less sense because you lose torque and fuel economy at low- and mid-RPM ranges. Keeping the exhaust valve open longer is what helps a street engine.
A number of changes in small- block Ford timing set configuration were made throughout this engine’s production life. You must pay very close attention to the changes to make sure everything works well together. Three basic thrust plates are available.
The C3OZ-B thrust plate has lubrication slots 180 degrees apart with a 47/64-inch center hole and two 19/64-inch bolt holes. The use of this thrust plate calls for a C2OZ-A timing sprocket. This applies to the 260-2V and 289-2V/4V engines. It does not, however, apply to the 289 High Performance V-8, which accepts a C3OZ-A thrust plate (3/8-inch thick) and compatible timing sprocket.
Small-block Fords manufactured after change “L7” in 1965 call for the use of one of three camshaft thrust plates: C9OZ-A is the standard 1/4-inch-thick thrust plate; C9OZ-B is .002-inch oversize; C9OZ-C is .004-inch thicker. These thrust plates have different thicknesses to take up endplay.
Three cam sprocket types were available from Ford: C3OZ-C iron sprocket for 221, 260, and 289-2V/4V engines; C3OZ-A iron sprocket for the 289 High Performance V-8; and C5OZ-B nylon-coated aluminum sprocket for the 289-2V/4V after change “L7” in 1965. The nylon-coated sprocket is strongly discouraged because, although quieter, it is not as durable and fails sooner. Nylon-coated gears were conceived for quieter operation; however, they’ve never been known for longevity.
Check camshaft endplay with the timing gear installed to determine which thrust plate/sprocket combination is correct for your engine. If endplay is significant, thrust plate and sprocket width should be thicker.
When you’re building a high- performance engine it is a good idea to opt for a dualroller timing set to ensure precision timing and durability. Dual-roller chains are less prone to stretch. If you have a dual-roller timing set, don’t forget to remove the crankshaft oil slinger, which can interfere with the timing chain and do severe engine damage. One solution is to flatten the oil slinger, which keeps it away from a dual-roller chain so you can still enjoy the benefits of an oil slinger. The crankshaft oil slinger serves two purposes: to sling oil onto the timing set and keep excessive oil away from the crank-shaft front seal.
Ford used several types of timing covers on small-block Fords from 1962 to 2000 and they’re all interchangeable, depending on your engine application. From 1962 to 1967, two cast-aluminum timing covers have cast-in timing pointers. The C4AZ-B (C2OE-6059-D) cover has a provision for an oil filler tube as you see on some but not all 1962–1964 221/260/289-ci small-blocks. The oil filler timing cover (C4AZ/C2OE-6059-D) was more common from 1962 to 1963 though not as common in 1964.
The Ford Master Parts Catalog lists change “L8” in association with the C4AZ-6019-B timing cover. With change “L8” came the timing cover devoid of the oil filler tube provision. The earliest versions of this timing cover with cast-in pointer were numbered C4AE-6059-B. In the Ford Master Parts Catalog, the suggested part number is D3OZ-6019-A, which is a universal timing cover with bolton pointer used from 1968–up, including the 351W.
Beginning in 1970, when the water pump inlet was moved to the driver’s side for improved radiator crossflow, the timing pointer was moved to the passenger’s side. This change came with a revised four-bolt harmonic balancer. The 1970 cross-flow radiator still had vertical tubes. In 1971, the crossflow radiators switched to horizontal tubes in most applications, for even better cooling.
When 5.0L and 5.8L engines first became equipped with Central Fuel Injection in 1980, Ford used a timing cover with a timing light magnetic pick-up point on the passenger’s side. Beginning in 1994, Ford went to a reverse-rotation cooling system with a different timing cover and water pump.
Another change was the elimination of the fuel pump provision sometime before the end of the 1993 model year.
The reverse-rotation water pump timing cover is easy to identify because the water pump is smaller and the timing cover is designed only for this water pump.
Valves, Springs, Retainers and Locks
The 221- and 260-ci V-8 engines stand alone when it comes to valvetrain components for several reasons. Valve size is the smallest of any small-block Ford, with a petite .310-inch stem, which is smaller than the 289/302’s .342-inch stem. The 351W has the same .342-inch size valvestem as the 289/302.
Boss 302 and 351C/351M/400M engines share the same basic cylinder head design. Like the 289/302/351W, the Boss 302 and Cleveland engines share the same valvestem size (.342 inch) with larger valve faces.
Valvespring keepers and retainers mandate close attention and with good reason. This is an area you do not want to overlook. The same can be said for valvesprings, which should be replaced anytime you build an engine. Valvespring pressures should always be compatible with cam lobe specifications. When you’re shopping for camshafts and valvetrain components, use the same brand in the interest of compatibility.
If you’re building a 260/289/302, opt for larger 1.94-inch intake and 1.60-inch exhaust valves for improved performance. Larger valves are an easy modification, especially when you’re getting a valve job anyway. New valveguides are mandatory. A shop can ream and bronze line existing guides, which is cheaper. You can improve oil drainback by opening up the drain holes in the cylinder heads.
Valves, springs, retainers, and locks play a very important role in engine reliability and security. Never reuse old valvesprings. The reason is that valvesprings experience cyclic fatigue through time and use. If valvesprings have been sitting in a stored engine for a long time, they’re no longer useful due to cyclic fatigue and spring compression where valves have been open for a long time. Never media blast or shot peen valvesprings for reuse either.
When you install valvesprings, make sure they’re indexed properly in the spring pocket. Ideally, you use a spring cup, which protects both spring and cylinder head. The 289 High Performance head has cast-in spring pockets. But you don’t need a Hi-Po head to have spring pockets. Be cautious in the way you handle valvesprings. Even a tool nick can lead to spring failure.
When you are installing valve- springs, closely examine keeper and lock compatibility for fitment. It’s a good idea to check installed height and spring pressure if you have the means. If you don’t have the right equipment, have a trusted machine shop check them. Also, have the machine shop install 16 new valves along with hardened steel exhaust valveseats for good compatibility with unleaded fuel. Have Viton valve seals installed, which offer excellent sealing and oil control.
When the small-block Ford was introduced, it was equipped with stud-mounted cast-steel rocker arms. Studs were pressed into the cylinder head with a tight interference fit. Pushrod guides were cast into the cylinder head. Rocker arms were fully adjustable, whether 221, 260, or 289 with hydraulic lifters. When the 289 High Performance V-8 was introduced for 1963, it was also fitted with adjustable stud-mounted rocker arms. The Hi-Po differed from the others in that screw-in rocker arm studs didn’t pull out of the head casting. Pushrod guides were also cast into the head.
In the interest of reducing production costs, Ford went to a rail-style rocker arm on May 2, 1966. The rail-style rocker arm eliminated the need for machining pushrod guide holes in the cylinder heads. Instead, longer valvestems and rocker arm guide rails kept the rocker centered on the valvestem. The only exception to this change was the 289 High Performance V-8, which was never fitted with a rail-style rocker arm.
Beginning in 1968, Ford went to a positive stop, no-adjust rocker arm stud pressed into the cylinder head that calls for a slow tightening process to allow for lifter piston movement and lockdown. The positive stop, non-adjustable rocker arm stud was in production from 1968 until the late 1970s when Ford adapted the Cleveland-style bolt-fulcrum stamped-steel rocker arm to the 302/351W small-blocks.
The 335-series 351C/351M/400 engines were manufactured with two types of valvetrain systems: bolt-fulcrum versions with stamped- steel rockers (351C-2V and 4V, 351M, and 400) and stud-mounted adjustable stamped-steel rocker arms (Boss 351 and 351 High Output). Bolt-fulcrum stamped-steel rocker arms were introduced on the 351C in 1970.
Although factory rocker arm systems work quite well and are certainly durable, they are not the most efficient rocker arm system. At the very least, you should use a roller tip rocker arm even if it’s one of the stamped-steel budget types. A roller tip isn’t as hard on the valvestem and it reduces internal friction.
It is advisable to spend the money for a good, high-quality full roller rocker arm such as the Comp Cams Pro Magnum because it employs rollers and bearings at the fulcrum and at the tip. What’s more, full rollers make a nice mechanical tappet chatter.
When you convert to roller rocker arms, keep valvecover clearances in mind. You need a minimum of 1/8 to 1/4 inch between rocker tip and valvecover. Sometimes, you can get away with a double-thickness valvecover gasket (available from sources such as Fel-Pro) and achieve the proper clearance. Other times, you need a valvecover spacer or different type of aftermarket valvecover for the clearance needed.
Although hundreds of thousands of small-block Fords were equipped with three-piece pushrods, you should use one-piece thick-wall pushrods for durability. The use of onepiece pushrods virtually eliminates the risk of failure unless you didn’t get the valvetrain geometry correct and there’s extreme stress on the rocker arm and pushrod.
Small-block Fords with a timing cover oil filler tube didn’t have a valvecover oil filler neck or a PCV valve. They had a draft tube at the rear of the intake manifold. Some applications even had a valvecover oil filler neck and a draft tube.
The first changes to small-block valvecover shape and design came on May 2, 1966, when Ford went to a rail-style rocker arm, which called for additional clearance between rocker arm and valve-cover. This change was known as a pent-roof-style valvecover (flat top) that was used until the end of 5.0L production in 2000. From 1962 to 1966, small-block Fords came with a slope-sided valvecover either with or without an oil filler tube and PCV valve provision.
Pent-roof-style flat-top valve-covers continued for 1968 with the words “Power By Ford” stamped into the cover. This designation was retained until 1975 when Ford changed to the corporate “Ford” oval, which continued through the early 1980s when Ford Blue gave way to a new corporate version of battle-ship gray.
With the advent of fuel injection came a passenger-side valvecover oil filler and a closed crankcase ventilation tube. When Ford introduced the 5.0L-2V High Output V-8 in 1982, finned cast-aluminum “Power By Ford” valvecovers became standard on the High Output, which were used through 1985.
When Ford introduced the 5.0L SEFI High Output V-8 for 1986, ribbed cast-aluminum valvecovers also arrived with a tall oil filler tube and crankcase ventilation on the passenger’s side. When the 1993 Mustang Cobra was introduced with a 5.0L GT-40 V-8, it had black stamped-steel valvecovers with the long oil filler tube with crankcase ventilation tube tied to the throttle body.
The greatest challenge you face in selecting valvecovers is valvetrain clearance issues. Aftermarket poly-locks and rocker arms don’t always clear the valvecovers. Rocker arm cover spacers and double-thickness valvecover gaskets are available, from Fel-Pro for example, that enable you to clear valvetrain components. Scott Drake valvecovers have unique oil splash baffles designed to clear all valvetrain components.
Written by George Reid and Posted with Permission of CarTechBooks