C3 Corvettes Engine Modification Guide - Chevy DIY (2024)

You have an enormous number of options for engines and engine modifications. Most Sharks are equipped with the small-block Chevy, and an almost infinite number of heads, cams, intake, exhaust, ignition, rotating assembly, and other performance part are available. You can build anything from a mildly modified street engine to a race engine. If you have or want to install a Chevy big-block, the number of modifications is nearly as extensive and diverse.

This Tech Tip is from the full book: CORVETTE C3 1689-1982: HOW TO BUILD AND MODIFY. For a comprehensive guide on this entire subject, you can visit this link:

LEARN MORE ABOUT THIS BOOK HERE

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I spent many of my early years pulling cylinder heads and replacing camshafts on a long weekend or two, looking for more power. Sometimes the correct decision was made in haste, and other times a decision was made in haste and a crucial step was missed. Proper and methodical planning is key to any engine project and most automotive projects. You need to develop a clear goal and work back from that to the beginning of the project so all the engine parts are compatible and complementary. But you also need to plan out each crucial step along the way so every step is completed correctly and professionally. Not having a clear goal always costs additional time and money; not evaluating the engine health can set you up for a major disappointment.

Your current engine should go through an evaluation and inspection process to determine what direction to proceed. Your engine may be in questionable health: adding performance pieces could add the death blow to an already worn-out engine. Mileage is usually a factor to take into account when engine health is considered. When the early Shark odometers turned over at 100,000, often the engine was in need of a rebuild. You need to perform an engine compression and/or leak-down test to determine whether the engine needs to be rebuilt. Cylinder compression is an important measurement of overall engine health. Leak-down testing is the best way to check for excessive crankcase pressure (blow-by, as it is often called), valve sealing, and head gasket integrity. As piston rings and cylinder walls wear, combustion gases are forced into the crankcase, creating the excess pressure. A good indicator of worn rings is seeing a steady puff of smoke belching from the valve cover’s PCV valve grommet.

Observing the oil pressure, especially once the engine coolant temperature reaches more than 180 degrees, is an important step in determining the engine’s rotating components’ health. With fresh oil, you should see 15 to 30 psi at idle with the pressure rising to a minimum of 50 to 60 at high RPM. On an extremely hot day, oil pressure may run as low as 10 to 15 psi at idle, and that is normal. However, the pressure must rise as RPM increases. Low steady oil pressure in the 25- to 30-psi range at high RPM is a warning. It is a clear indication of worn internal rotating components. Big-block engines have different oil pressure requirements from idle to wide-open throttle (WOT). Your big-block should idle with at least 30 psi; 35 to 40 is preferred for performance-use engines. Once the throttle is opened, you should see a minimum of 60 to 75 psi as you near the engine’s redline.

Inspection and Testing

A good procedure to determine engine health begins with a compression test to see if there are any variations in cylinder pressure. Variations in pressure could indicate leaking valves, blown head gaskets, or bent connecting rods. As you proceed to the leak-down test, you can determine if the low pressure is due to internal leakage or short connecting rods. When connecting rods bend, rod length gets shorter; consequently, cylinder volume is added and compression ratio drops. Make a note of the cylinders with lower pressure, as it is imperative to determine which cylinder is out of factory spec.

In some cases, something as simple as incorrect valve adjustment causes the problem. Removing the rocker arms during the leak-down test verifies the misadjusted valves if you record the findings from each test. Your spark plugs also indicate a worn engine if they have black crusty deposits. Black insulators warn you that the engine was running too rich, possibly washing the oil off the cylinders and causing excessive piston ring wear.

Parts Compatibility

Now that your engine’s health has been determined, you should consider its reliability factor as parts are chosen. Factory engine rotating components are typically adequate for up to 400 hp. If horsepower rises above 450, it’s tough on the bottom end, so don’t expect original-equipment rotating components to live long. As horsepower increases, reliability decreases. Now it’s time to make some choices.

Cylinder heads, camshaft, and compression largely determine the final power output of any given engine. At least 95 percent of an engine’s power is determined by the Big Three—this has been the rule in the past, and it will hold true in the future.

Essentially, engines are air pumps that perform best when the air entering and exiting the engine occurs as rapidly as possible. Installing high-flow aftermarket cylinder heads while using the factory intake and exhaust manifolds limits the cylinder head’s airflow design advantages. Installing a high-flow intake and exhaust with factory cylinder heads also produces minimal power gains. In addition, using the factory camshaft with new aftermarket performance pieces limits power gains as well. It should be evident that you need to select compatible and complementary components because the engine works as a system and the function and operation of one component directly affects another. You need to figure out the best intake manifold, cylinder heads, and camshaft for your application. Changing multiple components is another way to go until you hit something that “works” but that is costly and time consuming. I simply do not have the space to provide all the relevant options and combinations of engine parts for a wide range of C3 powerplants. How to Build Max-Performance Chevy Small-Blocks on a Budget by David Vizard and How to Build Big-Inch Chevy Small-Blocks by Graham Hansen are two excellent resources. They go into detail on building max-performance and stroker small-block Chevy engines.

Virtual Dyno Testing

You can back up the component manufacturers’ recommendations by using testing software, such as Virtual Engine 2000, which has proven to be very accurate. This product lets you input pertinent data, and then a virtual dynamometer pull is performed, showing you what power gain or loss the new component has contributed. The dynamometer software lets you check all the performance engine components you install, including the intake manifold, camshaft, exhaust system, and cylinder heads.

Desktop Dyno Engine Simulation is another virtual resource to ensure the correct performance parts combination. The same premise applies: input your engine data and test your performance parts choices. One advantage is that the Desktop Dyno software allows nitrous-oxide testing; at the other end of the spectrum fuel mileage can also be determined.

You can start component testing before the first wrench is turned. You need to know some very specific engine information for the most accurate end results. Keep in mind that guessing and inputting incorrect data can result in huge disappointments, or a major surprise with excellent power gains. Engine bore size, stroke, and combustion chamber volume can be found in factory service manuals after verifying your engine’s build codes. After you have taken some time to get acquainted with the software, figuring out the correct pieces is easy.

Intake Manifolds

An enthusiast often first installs an aftermarket aluminum intake manifold. Intake manifolds are typically single- or dual-plane design. Single-plane intakes typically have shorter, higher-angled runners (intake tracts) making the power band come in later, allowing higher RPM capabilities. Dual-plane intakes have longer and typically smaller-diameter intake runners, which enhance torque as they prevent reversion of incoming air while restricting high-RPM airflow.

If you want to make good torque at low RPM, dual-plane intakes are the ticket. If high-RPM horsepower is your game, select a single-plane intake manifold.

This Tech Tip is from the full book: CORVETTE C3 1689-1982: HOW TO BUILD AND MODIFY. For a comprehensive guide on this entire subject, you can visit this link:

LEARN MORE ABOUT THIS BOOK HERE

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The tough part of making an intake manifold decision is all the factors to consider. Larger-cubic-inch engines can provide plenty of torque with single-plane intakes, depending on many factors. Engine compression and camshaft selection, for instance, affect the torque output and, more important, when peak torque occurs. The smart plan is to carefully examine the possibilities and heed the manufacturer’s recommendations on the combinations that work.

The trick is balancing optimum intake performance with available underhood clearance when using factory hoods. In my experience, Shark owners rarely opt to install an aftermarket hood because they want to retain the factory look. Few single-plane intake manifolds fit under a stock hood. Typically, dualplane intakes sit much lower in the engine valley and allow the carb to fit under the stock hood. You need to select the entire intake package to clear the stock hood or you need to select an aftermarket hood that’s compatible with your intake package. That means the intake manifold, air cleaner, and yes, even the wing nut and air cleaner stud need to fit under the hood.

How to Measure Hood Clearance

Many GM and aftermarket intake manifolds are available. Each Shark is individual as body support cushions wear and hood clearances get tighter. The front-end bodywork often sags over time, which can be seen at the upper fender to door clearances. The gaps widen and the hood becomes closer to the air cleaner. You need to ensure that there is enough clearance between the air cleaner and the hood.

The only way to do that is to measure from the engine block intake manifold sealing surface to the hood. This determines whether there is adequate clearance. Aftermarket intake manifold manufacturers such as Weiand, Edelbrock, and Professional Products have fitment measurements on their websites, including how-to-measure instructions.

Once hood clearance is determined and a manifold is purchased, always check again for clearance before dropping the hood for the first time.

Replacing the Intake

The replacement of an intake manifold on the big- or small-block Chevy engine is one of the easiest mods to perform. Keeping things clean is the key; preparation and then torquing the intake bolts in sequence ensures a tight seal with no oil leaks.

Intake Manifold Installation

Step 1: Match Intake Ports on Cylinder Heads

I am beginning to port- or gasket-match this intake to a set of Patriot cylinder heads. This engine will be run at 6,500 rpm and above often. The port on the right is quite a bit smaller and would be fine for a low-RPM high-torque engine. If you plan on using out-of-the-box cylinder heads, one of the main concerns is to make sure the intake port is smaller than the cylinder head port to avoid airflow disturbance as the intake air and fuel enter the cylinder head. If the cylinder head ports are larger than the intake port, there is no need to do any machining if you plan on keeping the RPM below 5,500. Unless you just have to have matching ports, you don’t feel any performance gain.

Step 2: Prep for Gasket Install

I am prepping the cylinder head and engine block end surfaces for gasket installation. As you see, I have stuffed each port with paper towels to keep debris out of the engine. Previously the same blue towels were lying in the valley area to collect debris. If any debris falls into the lifter valley, take some time and remove it to avoid filling the oil pump pick-up tube with junk. I use naphtha, brake cleaner, or alcohol to wipe down all surfaces before placing the gaskets on the engine.

Step 3: Seal Engine Top End

Hot oil-resistant silicone sealer is used at the front and back of the intake manifold for the best sealing. Before we put the gaskets in place on this Racing Head Service cast-iron Vortec cylinder head, a dab of silicone is placed in the corner of the cylinder head and engine block below the gasket. Then silicone sealer is applied in a 3/16- to 1/4-inch bead ending approximately 1/4 inch up the intake gasket at the corners to prevent oil leakage. Not only does oil leak out, unfiltered air in the engine compartment can be drawn into the engine.

Step 4: Torque Intake Manifold

Proper sealing and torquing of the intake manifold are important if you want to avoid intake leaks and prevent distorting or breaking your aluminum intake. This Weiand intake on an early small-block requires bolt sealing to prevent oil from wicking up the bolt threads. I also apply Never-Seez to the outer four bolts to prevent rust or corrosion from forming in the threads if the intake gaskets weep coolant over time. Torque the intake manifold to the supplier’s recommendation, which is 35 to 40 ft-lbs. Take the extra time and read the instructions. Tighten the bolts in sequence and torque the intake bolts to their specs. Tightening sequence is equally important to avoid a cracked or broken intake flange. I use the tightening sequence for a preliminary hand tightening to seat the manifold, then go back and do the final torque. For the most part the tightening sequence starts at the center and works outward, alternating across the intake.

Cylinder Heads

Consider the following when selecting heads. Cast-iron cylinder heads are capable of making plenty of power for many reasons, including excellent thermal efficiency. Aluminum cylinder heads dissipate heat quicker, which drops combustion chamber heat, lowering their thermal efficiency. Cast-iron cylinder heads are much harder to port match and maximize flow with the denser material; because of this, few people use them as performance pieces. Aluminum cylinder heads are lighter weight, and the easy-to-modify intake tracts have made them very popular. Always consider the cylinder head’s combustion chamber size and piston configuration that affect your engine’s compression ratio. Higher compression ratios make more power and require higher-octane fuels.

Small-Block Cylinder Head

Original-equipment GM small-block heads have angled valves relative to the block deck. If you look at the top of the cylinder block, the valves are angled 23 degrees inward at the top toward the intake manifold area. Race-bred small-block cylinder heads have 18-degree valve angles, and the intake ports are not raised as high. This allows a smoother transition for incoming air into the cylinder head. The 18-degree heads require many extra pieces and are impractical when using a stock lower end with a cylinder head/cam change. In this section I only discuss the 23-degree version.

The 1968–1974 OEM Shark small-block (and big-block cylinder heads, by the way) has cast-in valve seats and valve guides. When unleaded fuels were introduced in 1975, valveseat temperatures were elevated, requiring tougher materials to withstand the heat. From 1975 on, General Motors installed replaceable hardened seats in its cylinder heads to handle the unleaded fuels.If you choose a set of pre-1975 GM cylinder heads for your project, expect to spend extra on machining and installation of hardened seats.

Excessive valve guide wear has been an issue on 1968–1982 GM heads. As the guide wears, it must be machined out and an aftermarket valve guide installed. Knurling is a less expensive alternative machine operation performed to tighten the valve in a worn valve guide. The cost of knurling is considerably less than replacing 16 valve guides. This is a temporary fix at best and not recommended for long-term performance use.

Check with your local machine shop about the cost; in the majority of cases, modifying original cylinder heads comes close to the cost of purchasing a set of aftermarket or GM performance cylinder heads. Your pre-1975 cylinder heads still have the same airflow rates and need a lot of work grinding on cast iron to achieve any dramatic results.

GM’s small-block performance aluminum cylinder head with D-shaped exhaust port is in plentiful supply and can be found on 1986 to late-1991 Corvette L-98 engines. General Motors designed the L-98 aluminum cylinder heads for the Tuned Port Induction (TPI) engine that made high torque at low RPM. The Corvette’s L-98 engine was breathing hard at 4,500 rpm because of the intake design, so the heads do not flow big numbers at high RPM. L-98 cylinder heads are good for 400 hp with plenty of torque in excess of 400 ft-lbs at or below 5,000 rpm. The L-98 cylinder head is relatively inexpensive and can be readily found at swap meets, so this makes them a deal unless you’re after high-RPM horsepower. To make high-RPM horsepower, they require plenty of porting work.

There is also a concern with the L-98 head’s limited valve-opening clearances, requiring extra pieces to make them compatible with high-lift camshafts. It makes sense to run the budget numbers before buying a used set of L-98 heads and then prepping them for high RPM with a high-lift camshaft.

General Motors made a really great-flowing OEM cast-iron cylinder head for use on 1996–1999 truck applications. The same Vortec cylinder heads were available from GM Performance Parts (now Chevrolet Performance) as an aftermarket replacement part. The Vortec heads had an improved combustion chamber, promoting better flow with a slight change in spark plug placement for better combustion. The heads are easy to spot because of their intake manifold retention bolt configuration. All Gen I non-Vortec cylinder heads use 12 bolts at a 90-degree angle to retain the intake to the cylinder heads. When the Vortec cylinder heads were introduced in 1996, 8 bolts at a 72-degree angle fastened the intake manifold onto the heads.

As you can imagine, when using GM Vortec heads the intake manifold must be replaced. The Vortec heads flow much better at low valve lift numbers than the late-1986–1991 Corvette L-98s, allowing horsepower to approach 480. General Motors redesigned the Vortec cast-iron head with taller, narrower intake runners and dual-bolt patterns with two port sizes (PN 25534421 for the small port and PN 25534431 for the large port). If you don’t mind a little extra weight, the Vortec head saves you a few dollars with airflow numbers approaching CNC-ported aluminum heads.

Big-Block Cylinder Head

GM big-block cylinder heads came in a large number of configurations on the early Shark, including oval-intake port for standard-performance and rectangular intake port for high-performance versions. Open and closed combustion chamber versions were also intermingled among oval- and rectangular-port cylinder heads. Oval-port intake runner volume is less than that of a rectangular port. Oval-port heads produce better low-speed torque output while hindering high-RPM power. Closed-chamber cylinder heads have less combustion chamber volume, which increases the compression ratio. Open-chamber big-block cylinder heads have better airflow characteristics with unobstructed valves.

The GM rectangular big-block cylinder head was offered in various aluminum versions. These special high-performance aluminum cylinder heads made it into limited production on Shark Corvettes with RPO L-89-optioned 427-ci engines. Casting integrity plagued the early big-block aluminum heads, so few were used in production or sold over the counter. These heads are rare pieces and best suited for high-end restorations.

You should consider buying a set of aftermarket high-performance heads that’s suited to your performance package rather than using limited-production Shark cast-iron big-block cylinder heads in a high-performance application. Let someone use the hard-to-find early big-block heads on a numbers-matching restoration.

This Tech Tip is from the full book: CORVETTE C3 1689-1982: HOW TO BUILD AND MODIFY. For a comprehensive guide on this entire subject, you can visit this link:

LEARN MORE ABOUT THIS BOOK HERE

SHARE THIS ARTICLE: Please feel free to share this post on Facebook or any automotive Forums or blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link: https://www.chevydiy.com/c3-corvettes-engine-modification-guide/

Aftermarket Cylinder Head

Most aftermarket cylinder heads are aluminum castings. However, cast-iron cylinder head companies, such as Racing Head Service, offer some excellent flowing iron heads that save you a few bucks. Although cast-iron heads are heavier than aluminum heads, the cost savings may steer you that way. Ultimately, a Shark’s front-to-rear weight balance is most important for handling. The majority of us cannot use the available power, and anything that improves handling makes better sense.

In most cases aftermarket cylinder heads have larger valves than stock heads to maximize airflow. They raise the intake port at the manifold area and modify the intake runner volume, maximizing the airflow into the intake valve area. Combustion chamber design is optimized to swirl the incoming air and fuel mixture for the best hom*ogenous flow into the engine’s cylinders.

Spark plug placement is also optimized for the best possible flame travel during the fuel’s ignition process.

Valveseat science has also grown tremendously, with five-angle seat machining replacing the three-angle seat formation that was used for many years.

Intake runner volume is a hot topic in the high-performance community. As with a small-diameter straw, it takes more effort to draw through it than with a larger-diameter straw. Having the highest flow numbers does not necessarily mean the best overall power combination. Low intake runner volume helps low-RPM torque by increasing the velocity of the incoming air into the cylinder. On the big end, though, it can hurt high-RPM power as a restriction.

Choosing the correct intake runner volume requires camshaft, intake, and vehicle usage info. A correctly set up intake, cylinder head, and camshaft features a single-plane intake for up to 7,000 rpm use, and a long-duration camshaft with 210-cc intake runner volume cylinder heads on a 350- to 383-ci engine. The opposite end of the spectrum is a dual plane intake for a maximum of 5,500 rpm, and a mild camshaft with 180-cc intake runner cylinder heads maximizing low-RPM torque for 350-ci engines.

A few manufacturers of ready-to-bolt-on performance cylinder heads make your task easier when it comes time to find the maximum horsepower. One of the top performers is Airflow Research (AFR). Great-flowing small- and big-block cylinder heads are what AFR is about, through many years of flow testing and tweaking for the most available power. Patriot Performance cylinder heads are another choice at excellent prices for the performance gain. Edelbrock has a number of options for both big- and small-block engines. They all have good products that provide out-of-the-box performance gains. The smart move is to contact them and see what they have to offer, then use their specifications for a run on your Desktop Dyno or Virtual Engine 2000 software. Don’t forget the intake manifold/hood clearance restrictions; that excellent-flowing cylinder head may not work as designed if the intake manifold is prohibiting airflow.

Cylinder Head Installation

The installation of heads typically takes a few days. Cleaning alone can take three to four hours when done properly but time spent cleaning makes the difference in keeping your engine alive for the most possible miles. Cylinder head gaskets affect sealing, compression ratio, and possibly valve-to-piston clearance. You need to pay particular attention to any recommendations the manufacturer provides.

Cylinder Head Installation

Step 1: Prep Block for Head Installation

This original 1969 Shark 350-hp engine had good compression and minimal leak-down, making it a good candidate to replace its original cast-in valve seat heads for a set of new, high-flow cylinder heads. This cleaning step is often missed during the installation phase. Thirty-two of the 34 head bolt threads are subjected to coolant, which prevents a proper tightening. The grit between the threads makes it feel as if you torqued the bolts to 65 ft-lbs, but in reality the threads are tight, not the cylinder heads. A 7/16- 14 thread tap is used for the clean out. Be careful when cleaning the top row of bolts; the tap can bottom out and break.

Step 2: Verify Trueness of Machined Surfaces

Central Tools provides precision measuring and testing tools such as this straightedge being used to check for cylinder head damage. The first step in checking the cylinder head for any distortion is to clean any carbon and gasket material from the surfaces. I left half of the cylinder head sealing surfaces as they came off the engine to show that there is quite a buildup of material that affects the testing procedure. The most common areas of distortion are between the cylinders. Place the straightedge lengthwise across the head surface. Insert a feeler gauge between the straightedge and the surface of the head. The .002-inch feeler gauge is being used to see if this cylinder head requires machining. The engine block should also be checked for any discrepancies, or you will pay the price in repeated head gasket failures.

Step 3: Prep Engine Block

Fairly new cotton T-shirt material works well for wiping down the block surfaces before gasket installation. But you need to be sure the rag is lintless, because you don’t want the fiber of the rag to get inside the engine and cause damage or potential failure. Coarse rags may leave behind lint on a recently machined cylinder head deck. Here, naphtha or brake cleaner removes any grease or oil left behind from piston installation. Any oil left behind prevents gasket material sealing, creating plenty of extra work when you find that the heads have to come off for another set of gaskets.

Step 4: Install Cylinder Heads

The task seems simple enough: Pick up the cylinder head and set it on the engine block. Aluminum heads make the job easier, but they, like cast-iron cylinder heads, can cut the head gasket or put a serious ding in it that will cause grief later. Try to set the head level and on the alignment pins, moving it around until it seats on the pins. If a sharp edge cuts into the gasket you could be doing this all over again. Combustion leaks can occur: once they do, they can do severe damage to the engine block and/or cylinder heads.

Step 5: Torque Cylinder Heads

This is serious stuff here, especially if you plan on putting some extra squeeze in the cylinder with nitrous or a supercharger. Torque the cylinder head bolts in sequence starting at 25 ft-lbs for the first pass, then another pass to 50 ft-lbs before tightening them to the cylinder head manufacturer’s recommendations. I have used this procedure for many years on supercharged and nitrous-equipped engines without gasket failure. Take the time to go over all the bolts one final time after you have done the final pass, torquing the heads to the manufacturer’s recommendations.

Camshaft Selection and Installation

As I mentioned earlier, using virtual dyno testing with computer software gives you information in addition to that from the manufacturer, but now it is time to make the selection.

In my mind, swapping a camshaft is less work than swapping the cylinder heads. Performing both operations at the same time makes plenty of sense because the labor overlaps and these components are interdependent. Again, cleanliness is the best policy, and torquing the fasteners is important.

Camshaft Swap

Step 1: Remove Harmonic Balancer

Harmonic balancer removal is the first step in camshaft removal and installation. The Shark’s crossmember is in the way, making it difficult to use anything but this long wrench to slowly force the balancer off the crankshaft. To avoid removing the transmission’s torque converter cover to hold the crankshaft during balancer removal, use large channel-lock pliers to hold on to the balancer removal tool.

Step 2: Remove Timing Gear

The small- and big-block crankshaft timing gear is pressed on, requiring a puller to remove it. This three-jawed puller does a good job of easing it off. I try to avoid applying heat with the gear in place, as crankshaft main bearing damage can occur. I also use a stop on the end of the crankshaft to avoid damaging the crankshaft balancer’s threaded hole during puller use. It is a good idea to change this gear even if the replacement chain and gear match the one in place: wear occurs and slack timing chains alter timing and performance.

Step 3: Remove Valve Lifters

Valve lifters can be very tough to remove from high-mileage engines for two reasons: sludge buildup and mushrooming of the lifter where it rides on the camshaft. My first suggestion is to use carburetor or throttle-body cleaner to soften the oil sludge deposits. Spray the cleaner on the sides of the lifter, then work the lifter up and down to knock off the sludge. This cleaning and working the lifter up and down can take awhile. If you feel that you need a hammer to get the lifter out, it is time to rethink the plan. Either the lifter is mushroomed on the bottom, or the sludge is so bad the engine will not live much longer even if you clean it up. Lifter bore damage can occur if a mushroomed lifter is forced out of the engine block. In that case you need more machine work than a typical rebuild. Bite the bullet and go through the engine, or get that crate engine you were considering.

Step 4: Install Camshaft

You can use a cam installation tool. Instead, I use this long number two Phillips screwdriver. When guiding the cam into the cam tunnel, keep the camshaft lobes from cutting into cam bearings as you work the camshaft out and it is seated into the correct position. Slowly move the camshaft to keep the lobes of the camshaft away from bearing surfaces. You can rest the cam on the bearing surfaces to regain a good grip if necessary as the camshaft is removed or installed. The lifters interfere with the cam during installation, so leave them out. The fuel pump needs to be removed to allow the fuel pump pushrod to fall away from the camshaft lobe.

Step 5: Install Camshaft Retainer Plate

This is a 1987 or later small-block with factory roller lifter camshaft. Position the camshaft retainer plate on the block. Squirt some Loctite on the screws and torque them to 20 ft-lbs. Early engines (non-roller lifter) do not require a camshaft retaining component unless a retrofit camshaft is installed. High-performance engine builders use a roller bearing under the camshaft gear and a roller button that rides on the camshaft timing cover to keep the camshaft from moving around at high RPM. Follow your camshaft manufacturer’s recommendations regarding the use of a retaining component on roller lifter camshaft retrofits.

Step 6: Degree the Camshaft

You need to degree the camshaft. High-performance engine builders pay careful attention to camshaft timing on every build, and so should you. This is an effort to extract every possible bit of power out of an engine. The use of computer testing software may have indicated that retarding the camshaft timing added horsepower at the top end where you really want it; degreeing the camshaft is the only sure way to know where the camshaft is sitting.

Step 7: Install Harmonic Balancer

I am a strong believer in this harmonic balancer installation tool as opposed to using a big hammer to pound it in place. Lisle makes an inexpensive version without a bearing under the forcing nut: it works well for someone doing one or two balancer installs per year. Major automotive parts chains also rent them at a reasonable cost, or you can buy one for about $45. Apply a light film of Never-Seez on the balancer’s inner hub to aid installation, and make sure to apply lubricant to the front crankshaft seal to avoid burning up the seal at startup.

Step 8: Adjust Valve Lifter

My favorite way to adjust lifters is to do it while the manifold is off. When it’s done this way, it is much easier to feel the load on the pushrods as the rocker nuts are tightened down. With each cylinder at top dead cylinder (TDC) on the compression stroke, this can be determined by placing the balancer on TDC for cylinder number-1 to begin with. As you watch the number-1 cylinder’s valves during crankshaft rotation, look for the number-1 cylinder’s intake valve to open then close. When that intake valve closes, begin watching the balancer. As the TDC mark on the balancer matches the zero on the timing cover tab, you are now at the cylinder number-1 TDC. Both valves can be adjusted on that cylinder. Rotate the balancer 90 degrees and adjust the next cylinder in the firing order, which would be number-8. Repeat the procedure using the firing order until all the valves are adjusted. The rocker arm adjusting nuts are tightened until the pushrod just begins to have drag on it while trying to rotate it. Once you feel the slight drag, turn down the nut is an additional 3/4 of a turn to center the lifter. All too often the rocker nuts are left loose to avoid lifter pump up at high RPM. But you cannot leave them loose because they beat up the valve stems and can cause them to fail at high RPM.

Step 9: Seal Oil Pan

I highly recommended one-piece rubber oil pan gaskets to avoid oil leaks. Apply two beads of hot oil-resistant silicone at the front and back of the oil pan to seal up any imperfections at the corners or in the oil pan itself. Once you apply the silicone to the gasket, put the gasket into the proper position as soon as possible. Within 10 to 15 minutes, the silicone provides good bite to the block surface. If the silicone gets too dry, it skins over and does not grip the metal or gasket. Have all the bolts and required tools ready nearby to keep moving once the pan is put into place.

Once you have all the work completed, you need to fill the crankcase with the proper engine oil and set up the engine for tuning. If you choose a flat-tappet hydraulic or solid lifter camshaft, you need to be very careful about what oil you put in the crankcase. Zinc has been phased out of engine oils as of 2007, which requires you to use a zinc additive to prevent cam lobe wear.

Joe Gibbs Driven Break-In Oil and others on the market have ZDDP. This additive can be found in engine oils designated as off-road or race blends. The story is the Feds want catalytic converters to last 100,000-plus miles, and the zinc was contaminating them. Engine oil manufacturers, such as Brad Penn, have multiple viscosities available with the proper zinc blended into each quart for long camshaft lobe life.

Kirban Motorsports has ZDDP in 4-ounce bottles to add to your favorite motor oil. Synthetic motor oils for late model engines do not have zinc and do not protect your camshaft; you must use the zinc supplement. The best policy is to check the contents of the oil before you drop it in the engine; no zinc, no go.

Written by Chris Petris and Posted with Permission of CarTechBooks

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