Timing Theory and Principles Variable Valve

There’s no doubt that engine specialists will begin seeing more variable valve timing (VVT) designed engines in their shops, as the generation of vehicles equipped with this technology begins to make its way into the service industry.  camsprocketVVT  .These camshaft sprockets and timing gears are integral parts on this Ford application. The stamped steel plates are reluctors that allow the camshaft position sensor to sense valve timing. A conventional timing chain sprocket completes the set. In fact, the current versions of VVT were popularly introduced into domestic production about 10 years ago.

Operating Principles

The theory behind variable valve timing is simple. Imagine a column of air speeding through a two-inch pipe at 250 feet per second. Suddenly, the air flow is blocked off by a valve at the end of the pipe. The kinetic energy of the air keeps it moving until a compression wave begins to develop at the valve. The optimum time to open the valve and achieve the greatest air flow is when this compression wave reaches its peak. In contrast, the best time to open the exhaust valve is when a vacuum wave develops at the valve. Variable valve timing takes advantage of these pressure and vacuum waves to achieve a greater air flow through a given size of engine. Advancing valve timing increases low-speed engine torque while retarding valve timing increases high-speed torque. The Powertrain Control Module (PCM) determines the valve timing position through data supplied by the camshaft position sensors or by valve timing sensors. Be aware of this terminology because some vehicles can use both types of sensors on a single engine.

Parts Nomenclature

The part that actually controls the camshaft position (and the valve timing event) is called a “phaser.” VVT Phaser design includes piston and vane-type configurations. In either case, the phaser uses engine oil pressure to push the piston or rotating vanes against a strong spring. With the vane-type phaser, a clock spring returns valve timing to a “default” position during engine start-up or if the VVT system fails. Another part, called a valve timing solenoid, meters engine oil pressure into the phaser. The VVT solenoid is supplied key-on voltage and the PCM momentarily grounds the circuit to meter oil pressure into the phaser until the valve timing reaches the desired value. The valve timing solenoid also includes a very fine-mesh screen to prevent sludge and debris from entering the mechanism.

Lubrication Issues

Since correct lubrication is critical to the operation of the VVT phasers and solenoids, it’s doubly important that the correct viscosity of oil is used in a VVT engine. Because VVT designs use a metered oil orifice to adjust valve timing, an oil with a higher than specified viscosity can cause false VVT trouble codes to be stored in the PCM. In addition, the oil must have the correct additive package to keep the engine’s oil passages, phasers, and VVT solenoid screens clean.


Standard and Reverse Rotation Marine Engines – What to Look For

 Standard and Reverse Rotation Marine Engines – What to Look For
Boats with twin engines usually turn in opposite direction so the torque reactions of the engines cancel each other out. The following four drawings show how the crankshaft and camshaft turn in the four combinations of drives. Some of the parts in these engines may be interchangeable, but will not function properly and can create problems for rebuilders.Gear Rotations





Crankshaft – Some of the reverse rotation cranks have the oil holes drilled symmetrically opposite. Check this closely.

Camshaft – In the above combinations none of the cams are interchangeable. The lobe timing and/or the distributor drive gear angle are different.

Distributor/Oil Pump – In all of the applications, we know of both the distributor and oil pump turn the same direction regardless of the crank rotation. This is done by making the angle of the drive gear on the cam and its mating gear opposite, when the cam turns the opposite direction. This makes the thrust of the gears in the opposite direction. For example, the SE Chevy thrust is up and is taken by the base of the distributor housing and the drive gear.

If the cam rotation and gear angle are changed, the thrust is down and there are no provisions for this in a stock distributor. A ball bearing distributor or magneto is required.
When working on marine engines, be sure you know what the components intended usage is and do not vary from it.


Effects of Sulfur Reduction in Motor Oils

The reduction of sulfur in diesel fuel, gasoline and motor oil has had measurable effects on fuel injectors and other vital engine parts. Add to that restrictions on additives like ­ZincDialkylDithioPhosphate(ZDDP), and it seems like the whole world of fuels and lubricants has turned upside down at times.

Before you let all this change give you a case of heartburn, remember that knowledge is power, so here is a summary of the changes in gasoline, diesel and motor oils. You can use this knowledge to steer clear of potential pitfalls as we navigate the new chemical landscape.

We’ll start with sulfur reduction. All crude oils contain sulfur. You may have heard of the term “Sweet or Sour” crude. This is in reference to the amount of sulfur in the crude oil. As a ­result, products of refined crude oil like diesel fuel, gasoline and conventional motor oils ­contain sulfur.

Today’s emissions regulations limit the amount of sulfur in all of these products. While this is a benefit for emissions, it does have some consequences. Primarily, sulfur is a natural ­lubricant, so reductions in sulfur reduce the ­natural lubricity of refined products. This has been evidenced in diesel engines since the ­advent of ultra-low sulfur diesel fuel. Problems with injector wear have been attributed to the lack of lubricity in this fuel type.

The sulfur reduction has also impacted both gasoline and motor oil. The lower level of sulfur in modern motor oils does reduce the natural lubricity of the oil. Starting in the mid-1990s, more and more motor oils are being blended from lower sulfur Group II and Group III base oils as opposed to the traditional, higher sulfur Group I base oils. Couple that with the ­reduction in ZDDP, and it is easy to see why premature camshaft and lifter wear has skyrocketed since the mid-’90s.

The effect of reducing sulfur in gasoline is not related to lubricity, but it is related to corrosive wear. You see, sulfur is not just a lubricant, it has an affinity for metal surfaces, which can prevent other chemicals from reacting with those metal surfaces. Couple the reduction in sulfur along with the advent of Ethanol in gasoline, and carburetors suddenly were at risk.

Again, the timing is similar. In the mid-1990s Ethanol began to be added to gasoIine just as the sulfur levels were reduced. By the mid-2000s, the critical point had been reached – there was too much Ethanol in the fuel compared to the level of sulfur and gasoline detergent additives.

The result was widespread corrosion in carburetors, which continues to this day. Ethanol is corrosive towards the aluminum, steel and Zinc alloys used in carbs, fuel pumps and fuel tanks, and now the fuel has less sulfur to protect those components from the Ethanol.

Couple that with lower levels of gasoIine detergents in pump fuel, and it is easy to see why carbureted engines from Big Block Chevys to two-stroke leaf blowers have been struggling in the past decade.

Ethanol Addition
The reduction in sulfur is not the only issue affecting fuel and lubricants. The drive to reduce emissions resulted in other chemical changes besides reducing sulfur.
One change we already mentioned is the addition of Ethanol to gasoline. This is directly related to emissions, and the advent of Ethanol-blended gasoline has been
effective in regards to emissions reduction.

However, the addition to Ethanol in gasoline has had other side effects – primarily corrosion. Ethanol is hygroscopic, which is a fancy way of saying that Ethanol absorbs water. The chemical cocktail of Ethanol and water is very corrosive to aluminum, steel and Zinc.

The presence of water in the fuel also speeds up the oxidation of the fuel – again, a fancy way of saying the breakdown of the fuel. When the fuel oxidizes, it can lead gummy deposits that affect the performance of both fuel injection systems and carburetors.

Because moisture contamination is related to storage time and conditions, daily drivers rarely see any of these issues.

However, vehicles that see long term storage and infrequent use tend to fall victim. Marine applications are the worst case scenario because they feature both high-moisture environments and long periods of storage.

Another area of chemical change is in motor oil. In order to provide better catalytic converter efficiency, the amount and type of additives used in motor oils have changed.
The most recent API SN and ILSAC GF-5 oil standards call for the use of a new type of ZDDP that provides better catalytic converter protection. At this you may be asking,“aren’t all the Zinc additives the same?”

The simple answer is – no. Several different compounds within the ZDDP family exist, and some are better at protecting catalytic converter performance than others.

These new additives are called Phosphorus Retention ZDDPs, and they have replaced the older-style ZDDP in API SN and ILSAC GF-5 motor oil formulas. While this is good news for modern engines and stock valve trains, engine testing has shown these new ZDDPs are not as good for the older style flat tappet valve trains.

Again, knowledge is power. Now that you are aware of these issues, you can easily take steps to avoid these problems.
Diesel engine owners have a variety of fuel additives to choose from that restore lost lubricity to ultra-low sulfur diesel.
Owners of street rods and lawnmowers alike can seek out non-Ethanol gasoline, or choose to treat Ethanol-blended gasoline with a corrosion and deposit-inhibitor additive.

These fuel additive products impart lubricity, corrosion protection and deposit control to readily available fuels and motor oils with boosted levels of ZincDialkylDithioPhosphate to provide the increased anti-wear protection older and high performance
engines need.


The universal engine oil is expected to die in 2016.


Diesel, gasoline and natural gas engine oils are going to be changing by 2016.

With the current regulatory emphasis on improving fuel economy, which also reduces greenhouse gas (GHG) emissions, engine oil scientists will soon be reformulating all three oils to improve fuel economy.

When the Federal government enacted fuel economy regulations for trucks, diesel engine builders in the Engine Manufacturers Association (EMA) asked the lube oil industry to help them meet these requirements by developing a new diesel oil performance category (PC-11), which would define oils providing better fuel economy and increased compatibility with biodiesel fuels. Development has been underway for at least two years.

The initial change, which will be made to diesel oils to improve fuel economy, is to lower viscosity. When engines are properly lubricated, a hydrodynamic film exists between engine components. Larger engine component clearances (primarily bearing clearances) require higher viscosity oils to provide hydrodynamic lubrication.

Racers build engines with extremely tight clearances in order to reap the horsepower benefits of these low viscosity oils, but diesel engine builders haven’t yet had sufficient time to research reduced bearing clearances.

If you are interested in lower viscosity oils, evaluate thinner engine oils in your fleet one viscosity grade at a time after conferring with your engine manufacturer.

Since most (83%) North American heavy-duty diesel oil is SAE 15W-40, primary effort has been focused on reducing oil viscosity to improve fuel economy in engines with clearances designed for SAE 15W-40 oils. Future developments will no doubt include research into using friction—modified oils to further improve fuel economy.

Biodiesel is being ignored at this time. The new PC-11 category will most likely specify two oils—a low viscosity oil for use in 2014 and later model year engines, and a more viscous oil for use in older engine designs. Look for completely new diesel engine oils that should yield improved fuel economy by 2016.

New passenger car engine oils called API SP and ILSAC GF-6 are also being developed for introduction in 2016. The major driver for these new oils is also fuel economy and fuel economy retention throughout the oil change interval. Passenger cars do utilize friction—modified oils, but these additives can sometimes be depleted prior to the oil being changed.

Environmentalists are also asking for a further reduction in oil phosphorus levels from the current GF-5 maximum of 800 ppm % wt. Their objective is to extend catalytic converter service life, but I’ve seen no evidence of field problems. Reduced phosphorous limits means reduced extreme pressure (EP) protection for highly-loaded engine components. Although new engine designs can reduce component loading to deal with reduced phosphorous oils, existing engines are vulnerable. High performance valvetrains are particularly susceptible.

Oils for engines using natural gas traditionally have been developed directly with engine OEMs in the absence of universal standards. These oils are much more oxidatively stable than diesel oils, so they need far less detergency and dispersancy. These manufacturers will have to investigate fuel economy for engines operating under stop and go conditions as well as steady state.

For years, fleet operators have been using “universal oils” in both diesel and gasoline fuelled engines. Honda favors SAE OW-16 oils for their new passenger car engines. I doubt that diesels can survive on oils that thin. I also doubt that highly stressed fuel injection components can achieve satisfactory service life on oils containing less than 800 ppm % wt. phosphorus.

Using an oil that meets current API diesel oil specs in a gaseous fuel engine is wasting money. In 2016 fleet operators should concentrate on using the optimum engine oil for each engine/fuel

The universal engine oil should die in 2016.


Common Causes of Water Pump Failure

1. Failure Symptom: Seal Leakage-Dirty System

Evidence of seal leakage from weep hole  – This pump has been in service only a short time before rusty-looking coolant began to leak out of the weep hole, leaving behind large deposits of rust and calcium.  Figure 1 shows a buildup of rust particles with a mud-like consistency within the pump.

Cause of Failure: Cooling System Contamination

The abrasiveness of the particles found in a badly contaminated system will prematurely wear the water pump seal . Harmful contamination is common in systems that are not properly maintained.  A system that is not properly pressurized will allow air to enter and promote the build-up of rust.  If water with a high mineral content is added to the system and is heated, it will begin to form deposits that will accumulate and cause passage restrictions, which may damage the seal.

Remedy:  Thoroughly flush a contaminated system BEFORE replacing the water pump. Check system pressure, use correct coolant mixture, and consider using distilled water where locally deemed necessary.

2. Failure Symptom: Shaft Breakage

A break usually occurs through the front bearing race portion of the shaft. This particular break can be noted by a clean fracture, rather than blue heat discoloration, which can appear in this same type of failure .

Cause of Failure: Bearing Overload

This bearing failed as the result of a sudden overload caused by vibration or imbalance.  The lack of heat-related discoloration indicates that this was sudden rather than gradual, and was probably compounded by rapid engine acceleration.  Blue discoloration of the shaft would indicate that there was excessive heat build-up for some period prior to shaft breakage.  This heat build-up can be caused by the tremendous centrifugal forces created by imbalance.  This overloads the bearing generating a great deal of heat.  This load is amplified through rapid acceleration and high RPM operation.

Remedy:  Carefully check alignment of all pulleys.  Also check the pulleys for straightness or fatigue.  Install belts using a belt tension gauge according to manufacturer’s recommendations.  Carefully inspect fan/fan clutch assembly for a bent or damaged fan, a worn spacer, or a worn or damaged fan clutch.  Be sure to evenly tighten the mounting bolts to manufacturer’s specifications.

3. Failure Symptom: Casting Breakage

This breakage will normally occur around the bearing support .

Cause of Failure: Excessive Vibration

Casting failure is normally associated with heavy vibration or imbalance which can be caused by a badly worn fan clutch or bent fan.

Remedy:  Carefully inspect pulley, belt alignment and fan/fan clutch assembly, replacing any bent or worn components.

4. Failure Symptom: Seal Leakage-Clean System

Leakage was observed from this pump, which had just recently been installed in a fairly clean cooling system .

Cause of Failure:  Thermal Shock

The seal was more closely inspected after no signs of contamination were observed. This revealed that the seal damage had come from thermal shock, typically caused by adding cold coolant to an overheated engine. The damage appears as a diametrical crack across either the seal face or the mating ring.  This can also occur following water pump replacement if the engine is started before adding coolant.

Remedy:  Take proper precautions when filling your radiator, especially when the engine may be very hot.  Allow an overheated engine to sit and cool before adding coolant. Then, restart engine and allow it to run while slowly adding the remainder. NEVER start the engine without coolant.



Motor Oil Fact or Fiction

1. Synthetic motor oil is too slippery. It causes roller bearings to slide instead of roll, and that causes the bearings to fail.

Fact or Fiction? – Fiction

If you have ever flown on a jet airplane, you have enough experience to debunk this myth. All jet turbine engines utilize rolling-element bearings, and every jet turbine engine runs on synthetic oil. In fact, only synthetic oil can handle the high speeds and extreme temperatures found in turbine engines. This myth is very popular among the motorcycle crowd, and the roots of this myth are based in the misapplication of passenger car motor oil. The power density of motorcycle engines place greater shear forces on the motor oil than passenger car engines do. As a result, most passenger car motor oils are not appropriate for use in a motorcycle engine. This is especially true of passenger car motor oils optimized for passenger-car fuel economy. These oils are the least shear stable, and should not be used in motorcycle engines.

Failures in motorcycle engines have long been blamed on synthetic oil. However, the problem was is not the synthetic base oil, it’s the fact the synthetic oil is not formulated for a motorcycle engine. A properly-formulated synthetic motorcycle oil will provide superior performance in a motorcycle engine. Likewise, a properly-formulated synthetic passenger car motor oil will provide superior performance in a passenger car engine as well.

2. Flat tappet engines can’t use synthetic oil because the lifters won’t rotate – the synthetic oil is too slippery.

Fact or Fiction? – Fiction

This is a variation on the first myth that has become popular since flat tappet camshaft failures began to increase about 10 years ago. Like the first myth, the origin of this one also relates to misapplication of passenger car motor oil. About two decades ago it was common for racers to use off-the-shelf motor oils in their racing engines. At that time, these motor oils contained enough ZDDP (aka Zinc) to protect the aggressive camshaft designs found in racing engines. Because NASCAR teams raced for hundreds of miles each weekend at very high oil temperatures, it was common practice to use synthetic motor oils.

You could purchase premium synthetic motor oil right off the shelf back in the early 1990s that was capable protecting a flat tappet race camshaft. By the time 2005 rolled around, however, the ZDDP levels in off-the-shelf motor oils had been reduced due to EPA regulations for passenger cars, and this reduction in ZDDP found these formulations to be deficient for protecting flat tappet camshafts. As a result, the racers using off-shelf-motor oils began having camshaft failures, and because many racers used synthetic passenger car motor oils, it appeared the cause was synthetics.

Today, every NASCAR team still runs engines that use flat tappet cams, and every one of those flat tappet engines are lubricated with synthetic motor oils. However, these synthetic motor oils are special formulations with more ZDDP to protect the flat tappet camshaft. Again, misapplication is often the cause for problems that appear to be oil related.

3. Once you use synthetic motor oil, you can never change back to conventional oil.

Fact or Fiction? Fiction

An engine running conventional motor oil can change to synthetic motor oil, and you can change back to conventional if you would like. The likely start to this myth stems from an actual good practice – it is not a good idea to switch back and forth between different brands of oil. You’ve probably heard an old-school mechanic tell you to pick a brand and stick with it. That is a pretty good idea. However, it is more important to use the correct type of motor oil for your engine.

Most high performance and racing engines are actually initially broken in on conventional motor oil (specially formulated for engine break-in) and then switched to properly-formulated synthetic motor oil for use after the break-in process. Again, the key lesson here is to select an oil formulated for the specific needs of your application and then stick with that product.

4. Synthetic oils are bad for engines with old seals.

Fact or Fiction? Fact

You thought all of these would be fiction didn’t you? Well, this one turns out to be true in most applications. Notice we said most applications. While some exceptions to this rule can be found, the majority of times this rule does apply – don’t use synthetic motor oils in old engines with original seals.

When we say old engines, we mean engines that were built before 1992. Synthetic base oils are not compatible with many of the traditional seal materials, and even with “seal conditioner” additives, synthetic oils are harder on traditional seal materials than conventional oils. To avoid leaking seals, avoid very light synthetic motor oils in older engines. The low viscosity and resulting free flowing nature of the synthetic makes it easier for the oil to find a leak path. Higher-viscosity oils tend to leak less. Thus, most old-school hot rodders use thicker-viscosity conventional oils like a 15W-50 or 20W-50 in their engines.

Modern engines and modern seal materials are designed to be compatible with synthetic motor oils. This is so you can use a synthetic in a freshly rebuilt Small Block Chevy for your 1969 Camaro. If you have a ‘69 Camaro with the original seals though, then you should use a conventional oil. Now if you also happen to have a 2013 Camaro, you should use a synthetic motor oil in that engine.

Hopefully all of this puts to bed any worries or fears related to any myths you’ve heard about oil. More importantly, we hope you now see the importance of selecting the proper type of oil for the needs of a specific application. Just like a tailored suit fits the person it was tailored to better than an off-the-rack suit, application-specific formulas provide a better fit for the unique needs of performance enthusiasts than off-the-shelf motor oils.


Phaser-Style Variable Valve Timing System Controls and Operation

Vehicles with variable valve timing (VVT) have become commonplace over the last decade. Even more commonplace are engines that use a phaser to manipulate camshaft position and, hence, valve timing.
The phaser style of VVT is the focus of this article.
The oil control valve is the traffic control device of oil pressure. In this hold position, neither chamber receives pressure nor is drained.
Phasers commonly can be found on just the exhaust cam or on both the intake and exhaust cams.
Alteration of camshaft position changes the cam centerline and the lobe separation angle between intake and exhaust cams.
This gives engineers flexibility in improving fuel economy and power while continuing to meet emissions standards.
VVT presents additional diagnostic challenges and repair opportunities to the service industry including new trouble codes.
If you are not familiar with these units, it’s time to advance your diagnostic readiness by examining the VVT system, its controls and operation.
The oil control spool valve moves by PCM control of the solenoid. One set of chambers is pressurized while the opposite chambers are drained to create phaser movement.
Mechanical, hydraulic and electrical controls have been added to VVT engines.
Motor oil is the hydraulic medium that makes VVT work.
That means it is imperative that engines are filled to the correct level with clean motor oil of the proper viscosity.
Low oil level or the wrong viscosity can result in system slow response codes such as P000A or P000B and possible drive complaints including an illuminated MIL.
Oil pressure is critical, and as bearings wear and develop clearance, pressure will be affected.
The spool valve directs oil pressure and oil drain to move the phaser in the opposite direction
Engines are machined with additional oil galleys for VVT and are equipped with one or more fine mesh screens to prevent debris from entering components.
Replacing these screens often requires major engine disassembly.
Sensors that monitor oil pressure and oil temperature are common on VVT engines and are a part of system control strategy.
The major control component in camshaft phasing is the oil control valve (OCV). The OCV is a spool valve much like those found in automatic transmissions. The PCM (powertrain control module) duty-cycles a solenoid that alters valve position.
The OCV is an oil traffic control device of sorts. It determines which ports receive pressurized oil and which are vented.
These are the oil drain ports that allow oil directed by the OCV to drain into the front timing cover.
Pressurized oil travels through the OCV to one of the camshaft bearing journals. Oil flows though passageways inside and toward the front of the camshaft.
At the nose of the camshaft, oil enters ports of the camshaft ­phaser. The phaser is a mechanism with two major pieces, the rotor and the phaser body.

The oil control valve feeds or vents these camshaft bearing ports. Oil flows into and out of passageways inside the camshaft. The phaser body is physically bolted to the camshaft sprocket. The rotor is connected to the camshaft using a dowel pin.  The two pieces are able to move about 20° (40 crankshaft degrees) independently of each other. Ports inside the phaser direct oil in or out of eight chambers.Four chambers are considered side “A” and the other four are side “B.”As one group of chambers receives pressurized oil, the others are vented to ­provide the force necessary to move or hold the rotor relative to the phaser body.

 Internals of a cam phaser. The larger hole near the center at the 3:30 position is where the dowel of the camshaft locks to the phaser. The other four holes direct oil to and from the camshaft passageways. The outer body attaches to the cam sprocket. Also notice the oil seals that separate the oil chambers.
Oil seals fit into machined grooves of the rotor to provide a tight seal between the chambers.
Vented oil from the phaser ports travels back through the camshaft, the cam bearing ports, through the oil control valve and then drains into the front timing cover.
There is a mechanical device inside the phaser known as a lock pin.

The spring-loaded lock pin on the rotor engages into the phaser body to lock the two pieces together. The lock pin prevents noise and potential wear upon engine start. Oil pressure is required to disengage the lock pin.The 2.4L Chrysler engine that I disassembled also featured a spring on the exhaust camshaft.
The lock pin is on the rotor at right at about the 9 o’clock position. It locks into the phaser body at left. During low oil pressure events such as cranking, the pin locks the two components together to prevent noise and wear.
The locked phaser positions on this engine are full retard on the intake and full advance on the exhaust.Because of the clockwise rotation when viewed from the front of the engine, the exhaust rotor requires additional assistance in reaching the full advance position.
In the default position, there is no valve overlap. It should be noted that service information does not recommend phaser disassembly and ­individual parts are unavailable.
As for service parts, phasers are sold as an assembly.  Electrically, the OCV solenoid has two terminals. I measured the resistance of several solenoids from various manufacturers.They ranged between 7 and 12 ohms of resistance.
Both circuits connect to the PCM, which provides duty-cycle control either on ground or the insulated (power) side.I found versions of both on our laboratory vehicles. OCV solenoids are typically cycled upon ignition run mode as part of a cleaning and diagnostic strategy.Regardless of control specifics, the PCM monitors solenoid circuits for faults including opens, shorts to ground or shorts to voltage.


Camshaft Failure Reasons and Causes

Cam failure is rarely caused by the cam itself. The only things that can be controlled during manufacture pertaining to cam lobe wear are lobe taper, lobe hardness and surface finish.

  Of all the damaged cams that Mayor`s has checked over the years, it says more than 99.99 percent have been manufactured correctly. Some people have the misconception that it is common for a cast iron flat tappet cam to occasionally have a soft lobe. Crane says they have yet to see a cast iron flat tappet cam that had a soft lobe. When the cast core is made at the casting foundry, all the lobes are flame hardened. That process hardens all the lobes to a depth below the barrel of the core. That depth of hardness allows the finish cam grinder to finish grind the cam lobes with a Rockwell hardness above 50Rc. The generally accepted hardness on a finished cast cam should be between 48Rc to 58Rc. All of the finished cams that we have checked are always above 50Rc hardness on the lobes. Many outside factors, or a combination of factors, can cause cam failures. We will list some of the factors that have been determined may cause camshaft failure.

 Lobe wear, incorrect break-in lubricant. Use only the moly paste that is included with the cam from the manufacturer. This moly paste must be applied to every cam lobe surface, and to the bottom of every lifter face of all flat tappet cams. Roller tappet cams only require engine oil to be applied to the lifters and cam. Also, apply the moly paste to the distributor gears on the cam and distributor for all camshafts. For extra protection, an anti-wear additive should be added, such as Super Lube. Do not use synthetic oil during the break-in period. It is not recommended to use any type of oil restrictors to the lifter galley, or use windage trays, baffles,or plug any oil return holes in the valley. Oil has a two-fold purpose, not only to lubricate, but also to draw the heat away from whatever it comes in contact with. The cam needs oil splash from the crankcase and oil run-back from the top of the engine to help draw the heat away. Without this oil flow, all the heat generated at the cam is transferred to the lifter, which can contribute to its early demise.

 Correct break-in procedure. After the correct break-in lubricant is applied to the cam and lifters, fill the crankcase with fresh non-synthetic oil. Prime the oil system with a priming tool and an electric drill so that all oil passages and the oil filter are full of oil. Preset the ignition timing and prime the fuel system. Fill the cooling system. Start the engine. The engine should start quickly and run between 1,500 and 3,000 rpm. If the engine will not start, don’t continue to crank for long periods, as that is very detrimental to the life of the cam. Check for the cause and correct. The engine should quickly start and be run between 1,500 to 3,000 rpm. Vary the rpm up and down in this rpm range during the first 15 to 20 minutes, (do not run the engine at a steady rpm). During this break-in time, verify that the pushrods are rotating, as this will show that the lifters are also rotating. If the lifters don’t rotate, the cam lobe and lifter will fail. Sometimes you may need to help spin the pushrod to start the rotation process during this break-in procedure.

 Lifter rotation is created by a taper ground on the cam lobe and the convex shape of the face of the flat tappet lifter. Also in some cases, the lobe is slightly offset from the center of the lifter bore in the block. If the linear spacing of the lifter bores in the block is not to the correct factory specifications, or the angle of the lifter bore is not 90 degrees to the centerline of the cam, the lifter may not rotate. Even if the engine you’re rebuilding had 100,000 miles on it and the cam you removed had no badly worn lobes, this still doesn’t mean that your block is made correctly. It just means that the break in procedure caused everything to work correctly. Be careful to watch the pushrods during break in to verify lifter rotation. Don’t assume everything will work correctly the second time.

 Always use new lifters on a new flat tappet cam. If you are removing a good used flat tappet cam and lifters and are planning to use them again in the same (or another) engine, you must keep the lifters in order as to what lobe of the cam they were on.    The lifter breaks-in to the specific lobe it is mated with and it can’t be changed. If the used lifters get mixed up, you should discard them and install a new set of lifters and break the cam in again as you would on a new cam and lifters. You can use new lifters on a good used cam, but never try to use used lifters on a new cam. Roller tappet cams don’t require any break-in. You can use roller lifters over again on a new cam if they are in good condition. There will be, of course, no lifter or pushrod rotation with the use of a roller tappet cam.

 Spring pressure. Normal recommended spring seat pressure for most mild street-type flat tappet cams is between 85 to 105 lbs. More radical street and race applications may use valve spring seat pressure between 105 to 130 lbs. For street hydraulic roller cams, seat pressure should range from 105 to 140 lbs. Spring seat pressure for mechanical street roller cams should not exceed 150 lbs. Race roller cams with high lift and spring pressure are not recommended for street use, because of a lack of oil splash onto the cam at low speed running to help cool the cam and lubricate the lifters. This high spring pressure causes the heat created at the cam to be transferred to the roller wheel, resulting in its early failure. Any springs that may be used must be assembled to the manufacturer’s recommended height. Never install springs without verifying the correct assembled height and pressures. Increased spring pressure from a spring change and/or increased valve lift can hinder lifter rotation during cam break-in. We have found that decreasing spring pressure during the break-in period will be a great help. This can be accomplished by using a shorter ratio rocker arm to lower the valve lift; and/ or removing the inner spring, during the cam break-in time, if dual springs are being used.

 Mechanical interference. The following are some of the factors that can cause mechanical interference: pring coil bind: This is when all of the coils of the spring (outside, inside or flat damper) contact each other before the full lift of the valve. It is recommended that the spring you are using be capable of traveling at least .060″ more than the valve lift of the cam from its assembled height. Retainer to seal/ valve guide boss interference. You need at least .060″ clearance between the bottom of the retainer and the seal or the top of the valve guide when the valve is at full lift. Valve to piston interference: this occurs when a change in cam specs. (i.e., lift, duration or centerline) is enough to cause this mechanical interference. Also: increased valve size, surfacing the block and/or cylinder head may cause this problem. If you have any doubt, piston to valve clearance should be checked. Minimum recommended clearance: .080″ intake and .100″ exhaust.

 Rocker arm slot-to-stud interference: As you increase valve lift, the rocker arm swings farther on its axis. Therefore the slot in the bottom of the rocker arm may run out of travel, and the end of the slot will contact the stud and stop the movement of the rocker arm. The slot in the rocker arm must be able to travel at least .060″ more than the full lift of the valve. Some engine families, like small block Chevrolet, have stamped steel rocker arms available in long and extra long slot versions for this purpose. Distributor gear wear. The main cause for distributor gear wear is the use of high volume or high-pressure oil pumps. We don’t recommend the use of these types of oil pumps. If you do run these types of oil pumps, you can expect short life of the cam and distributor gears, especially for low speed running, in street type applications. If you must run these types of oil pumps, you can increase the life of the gears by adding more oil flow over the gear area to help cool off the point of contact.

 Distributors that have end play adjustment (up and down movement of distributor shaft and gear) should maintain a maximum of .010″ end play to help prevent premature wear. Camshaft end play. Some engines have a thrust plate to control the forward and backward movement of the cam. The recommended end play on these types of engines is between .003″ to .008″. Many factors may cause this end play to be changed. When installing a new cam, timing gears, or thrust plates, be sure to verify end play after the cam bolts are torqued to factory specs. If the end play is excessive, it will cause the cam to move back in the block, causing the side of the lobe to contact an adjacent lifter. broken dowel pins or keys. The dowel pin or woodruff key does not drive the cam; the torque of the timing gear bolt, or bolts, against the front of the cam drives the cam.

 Some reasons for the dowel pin or key failing are: Bolts not being torqued to correct specs; Incorrect bolts of a lower grade being used; Stretching and losing torque; Not using the correct hardened washer that may distort and cause torque of the bolt to change; Thread-lock not being used; Or some interference with the cam and lifters or connecting rods causing the cam to stop rotation. Broken cam. A broken cam is usually caused by the cam being hit by a connecting rod, or other rotating parts of the engine coming loose and hitting the cam. When this happens, the cam will usually break in more than two-pieces. Sometimes the cam will break in two pieces after a short time of use because of a crack or fracture in the cam due to rough handling during shipping, or some time before installation. If a cam becomes cracked or fractured due to rough handling, it will generally not be straight.

 Most people will not have any means of checking cam straightness. As a general rule, if you can install the cam in the engine and install the timing gear, the cam should turn freely with just your finger pressure. There should not be any drag or resistance in turning the cam. This free turning of the cam is assuming that if new cam bearings were installed, they were the correct parts and they were installed correctly. When removing a used cam that may be worn, you may have difficulty turning or removing it. This may not mean that the cam is cracked or fractured. The heat generated at the cam during the failure of the cam lobe, and/or lifter, will distort the cam and cause it not to be straight any more.


Three Important Elements Around the Top Corner of a Piston

On forced induction and on nitrous applications, which experience extreme shock loads, Mayor`s says they move the top ring down from the piston crown to around .300˝. However, depending upon valve configuration and the positioning of the valve reliefs, the top ring can be moved down by as much as .450˝. But on most small-block applications with standard in-line valves and a power adder, setting the top ring at around .300˝ protects the top land and the top ring from slight detonation and other conditions that may occur in forced-induction applications.

With the top ring positioned at a dimension of .260˝ down from the piston crown, the piston will accept 250 to 260hp shots of nitrous.  The big consideration with nitrous, Mayor`s says, is air-fuel ratios. If they are inconsistent no amount of top-ring-down will save the piston.

On naturally aspirated engines a higher placement of the top ring is desirable. As a result the crevice volume between the piston and the cylinder is smaller. The higher placement of the top ring also induces the induction gases to enter the chamber faster, as smaller crevice volumes provide quicker reactions to the initial pull. Super Stock racers, whose engine changes are closely regulated, always place the top ring as high as possible


Machining an Engine Block

If you’re fortunate enough to have more than one engine block to choose for machining an if you haven’t yet purchased one, here are some obvious things to look for.First, Before machining an engine block you want to look for cracks on the water jacket area and in the lifter valley area. an If the block has ever been frozen, this is where cracks will show up. Next, look for cracks around the main webs, these are hard to spot when the block is greasy, but we are just looking for obvious cracks now.

If the webs check out okay, unbolt the main caps and look at the bearing seats for evidence of a spun bearing. If one or more of the seats look rough, and the material is blackened from heat, the block is not going to be suitable for performance use.

Provided the seats all look okay, place the main caps back on the block. They should snap into the block registers nice and snug. If they fit loosely, the caps will slide around under pressure and could cause a main bearing failure. After the main caps pass inspection, start checking for core shift.

Core shift occurs at the foundry when the blocks are being cast. The internal core will shift from the external core during casting, resulting in an “off center” block. The biggest problem with this is an un-uniform cylinder bore thickness. It is of utmost concern when using large overbores or very high horsepower.

The easiest way to check for core shift is to look at the cam and lifter bores. If they are in the center of the cast bulkhead in the block, the core didn’t shift too much, if they are way off center the core did shift. A block with a moderate amount of core shift will still be okay for performance use.

Once you’ve found a good core to start with, the first thing that needs to be done is get it cleaned. There are two basic options here: hot tanking or baking and peening. Peening does a much nicer job of removing scale and rust from the block. Peening is how we clean all of our race blocks, but it does cost a few dollars more, and it does rough up the machined surfaces a little. So, if you are planning on getting away with as little machine work as possible, hot tanking may be better for your job.

After the blocks are cleaned, check it for cracks using magnetic particle inspection. Again, they’ll be a lot easier to spot on a clean block. If no cracks are found, it’s time to start machining the block.

For stock rebuilds or very mild performance use, start by checking the cylinder head mounting surface. If it’s flat and not warped, it won’t need to be “decked.”

Next, check the main bearing housing bores, if they are in close alignment and the diameter is in the factory specified tolerance, it won’t need to be align honed. If everything checks out okay, all the block should need is bored and honed to fit whatever piston you are using.

For high horsepower applications, you must be more particular about tolerances, so we recommend decking the block. By doing this, you can achieve the desired surface finish for whatever gasket is used. Ensure that the decks are parallel to the crankshaft axis, and at the proper height to get the quench that you want, (quench is the distance from the flat portion of the piston, to the flat portion of the cylinder head).

When boring a block that has been decked, the cylinder bore becomes perfectly perpendicular to the crankshaft axis, which will help ring seal and reduce side loading of internal engine parts. When honing a high horsepower block, a torque plate should be used. This is a thick steel plate that is torqued to the deck with the cylinder head fasteners, this simulates a head being torqued to the block. Torquing a head down on a block creates imperfections in a cylinder bore, by using a torque plate, you can hone them to near perfection.

The main bearing housing bores are machined with a boring tool from the factory. This leaves a moderately rough finish for the bearing to rest against, so the actual contact area is reduced to where the bearing contacts the high spots on the surface of the bearing seat. For any high horsepower application, the block should be align honed. This ensures that the bores will be in perfect alignment and also provides a very flat, smooth bearing seat.

Depending on the application, budget and horsepower levels, it is sometimes necessary to use billet splayed bolt main caps. These are much wider than stock caps and the outer bolts reach into the sides of the block adding to the strength and reliability of the main webs.

This should cover most of the major stuff you’ll need to be concerned with. There are some oil and cooling system modifications that could be beneficial, but they are very application specific and should be determined by your needs.